GPS World

Tag: Survey Scene

  • LightSquared: High-Precision Receivers Are Collateral Damage

    Originally, the LightSquared/GPS Technical Working Group’s (TWG) report was due to the FCC on June 15, 2011. LightSquared requested from the FCC, and received, a two-week extension to submit their report. Three days later, LightSquared announced it found a solution to the GPS interference problem. Its new proposed solution is not good news for the high-precision GPS user community. Instead, it’s a threat directed squarely at high-precision GPS users like you and me. Do you recall what I wrote a month ago? It’s ringing true with the latest LightSquared proposal.

    “I’m going to keep this simple. You, the high-precision GPS user, are likely going to be considered collateral damage.

     

    The military is going to be accommodated in the name of national security. The aviation industry is going to be accommodated in the name of safety-of-life. The auto navigation industry is going to be accommodated because they are high-profile. The high-precision user is going to be thrown under the bus because we are the most difficult to accommodate (technically) and don’t have a high profile nor are perceived as significant enough to accommodate.”

     

    If you recall, the TWG consists of LightSquared and GPS industry representatives tasked with testing the effect that LightSquared’s proposed system may have on GPS. Four of the five sub-teams were ready to file their final report with the FCC on June 15. LightSquared’s sub-team, according to the Coalition to Save Our GPS webinar on Thursday June 16, was only sub-team not ready to file its report.

    Ok, so after the FCC granted LightSquared the two-week extension, I’m thinking we have a two-week hiatus from the LightSquared discussion as LightSquared compiles and prepares their July 1 submission.

     

    Nope, not a chance.

    On Monday, a mere three business days after they requested a two-week extension from the FCC,  LightSquared announced they’ve found a solution to the GPS interference problem and issued a statement titled “LightSquared Solution to GPS Issue Will Clear Way for Nationwide 4G Network.”

    LightSquared’s solution is to temporarily abandon the upper frequency they originally planned to roll out (1550-1555 MHz) and rollout its service using the lower spectrum I refer to as “modified” (1526-1536 MHz) in Figure 1.

    It’s important to remember that the lines separating frequency spectrums are not “brick walls.” There is signal “roll off” that results in a gray area between spectrums. That’s the reason the LightSquared upper frequency at 1550-1555 MHz was slamming GPS. Even though it is apparently separated from GPS L1, the sheer power of the LightSquared signal at 1,500 watts significantly bled into the red RNSS zone (1559-1610 MHz) in Figure 1.

     

                                                  Figure 1: FCC Spectrum Dashboard

    Using only the lower frequency spectrum (1526-1536 MHz), LightSquared claims that they are “largely free of interference issues with the exception of a limited number of high-precision GPS receivers that are specifically designed to rely on LightSquared’s spectrum.” LightSquared’s CEO said that this solution will accommodate 99.5% of the GPS receivers.

    Uh oh, guess who the remaining .5% are? Yes, your high-precision GPS receiver. One half of one percent is about the percentage of high-precision GPS receivers with respect to the total GPS market size in the U.S.

    I’m pretty confident that LightSquared isn’t weighting the receivers, so that means a $2 GPS chip inside a mobile phone carries the same weight as your $15,000 RTK receiver. But obviously the impact on our infrastructure and economy differs by orders of magnitude between the two.

    Remember last month when I wrote that high-precision GPS receivers might be thrown under the bus and considered collateral damage (LightSquared: It’s Worse than You Think)? The latest LightSquared proposal is what I was referring to. High-precision GPS receivers are the most difficult to accommodate, and LightSquared is thinking that if they tell the FCC (and the world) that they’ve taken care of 99.5% of the GPS receivers in the U.S., the other .5% can deal with it.

    It’s not yet clear how LightSquared broadcasting on 10L (1526-1536 MHz) will affect high-precision receivers. We should see some of those details at the end of the month when all reports are filed with the FCC.

    But either way, it’s clear that LightSquared broadcasting in the 1526-1536 Mhz spectrum would slam OmniSTAR and Deere & Co. Starfire users as you can see in Figure 1.

    Not so fast, say GNSS engineers. What about GLONASS, Galileo, and Compass?

    Russia’s GLONASS satellites are increasingly being used by high-precision receivers. In fact, it’s safe to say that all major manufacturers sell GPS/GLONASS receivers, which is an expensive option on most receivers. However, it’s relatively easy to justify the additional expense due to the productivity gains from the additional GLONASS satellites. Generally speaking, more satellites equals less down-time.

    The problem is that the U.S. government has no vested interest in protecting the GLONASS spectrum.

    The FAA doesn’t care about it. The U.S. military doesn’t care about it. The first-responders don’t care about it. Although GLONASS is starting to show up in consumer GPS chips, it’s not being used in those markets like it is in the high-precision markets such as surveying, engineering, construction, agriculture, GIS, and various machine control applications. Therefore, no GLONASS testing was performed at the Maryland test site (simulator not configured to output GLONASS) and little or no testing was done using GLONASS at the New Mexico or Las Vegas sites unless individual companies took it on themselves.

    Some say that GLONASS will get hammered by LightSquared mobile phones.

    To this point, most of the talk has been about GPS interference from LightSquared transmitters in the 1525-1559 MHz spectrum. We also need to be aware of LightSquared mobile phones, of which they intend to field 250 million — 100 million by the end of 2012. While LightSquared has control over the filtering on their transmitters, it have no control over the filtering used in mobile phones designed to use their system.

    I’ve heard there is some mention of LightSquared mobile phones in the reports that are to be filed with the FCC, but not made public yet. However, no LightSquared mobile phones exist today so it’s only possible to simulate them in a lab environment using a lot of design assumptions.

    The uplink frequency used by LightSquared mobile phones (to talk to the nearest tower) is in the range 1626.5-1660.5 MHz. That frequency is getting close to the top end of GPS and really close to GLONASS L1 which has a range of ~1598-1605.4MHz.

    According to one RF engineer I’ve spoken to, “We already know that Iridium (1616-1626.5 Mhz) and Inmarsat cannot co-exist in the upper band and seeing that the LightSquared handset transmit frequency is in that same spectrum, I think GLONASS in the U.S. is toast.”

    The future of GNSS receivers is definitely trending towards integrating GPS, GLONASS, Galileo, Compass, etc. signal
    s. A section of the NPEF report (mentioned above) succinctly describes the interference issue with GNSS receivers.

    Another approach examined involves limiting the LightSquared transmissions to the lower 5 or 10 MHz channel of their planned deployment. However, while this approach would protect a limited number of GPS applications other applications would still be susceptible to interference. Using this approach it may be possible to protect classes of GPS receivers, primarily those with greater receiver selectivity. However, some classes of GPS receivers would still not be protected under this mitigation technique. Receivers having wider RF front-end characteristics, such as those used for scientific and commercial uses requiring high-precision measurements, and some receivers capable of receiving multiple signals from different GNSS systems (e.g., GLONASS) would remain susceptible. Additionally, the use of only the lower LightSquared channel would provide only a temporary solution to the existing interference problems as 4G LTE levels of service may not be possible. Thus, even if allowed, the FCC’s objectives and service conditions on the LightSquared license would not be met.

    Finally and on a slightly different note, the future GPS L1C signal and L1 signals proposed by Galileo and Compass are a wider band than the current GPS L1 CA, which means they are likely more subject to interference from the LightSquared system.

     

    FCC Chairman Julius Genachowski: “As I have stated previously to Congress, the commission will not permit LightSquared to begin commercial service without first resolving the commission’s concerns about potential widespread harmful interference to GPS devices. Under no circumstances would I put at risk our nation’s national defense or public safety.”

    The FCC has stated on numerous occasions that LightSquared won’t be allowed to begin commercial service until GPS interference issues are resolved, but what does that really mean?

    Chairman Genachowski has also stated that “It should come as no surprise to anyone involved in the LightSquared matter that the company was planning for some time to deploy a major terrestrial network in the spectrum”. He’s implying that all parties involved should have prepared for this moment, and if the GPS industry didn’t, it should bear some of the burden. This is bad news indeed.

    Bottom line: The FCC is not looking out for your interests. The National Broadband Plan is heavy on their minds. I can clearly see the FCC thinking “in the interest of the bigger picture, the high-precision GPS user community can deal with it since its only .5% of the total GPS market.”

    We need to squash this new proposal by LightSquared in a hurry. It’s a threat directed squarely at the high-precision GPS user community.

     

    LightSquared Consultant claim: in the GPS industry’s “insatiable thirst for precision,” it made poor engineering decisions that made GPS receivers more vulnerable to interference from neighboring bands.

    Although it appears the statement is from an independent consulting firm, PRTM consultant Dan Hays is a Harbinger crony so don’t let it fool you into thinking it’s anything but another piece of LightSquared propaganda.

    But, let’s visit the subject for a minute to clarify because LightSquared has also claimed that high-precision GPS receivers are somehow at fault because they “are looking in our spectrum”.

    Jim Kirkland, VP and General Counsel for Trimble Navigation, said it well when I presented Mr. Hays’ statement during the Coalition to Save Our GPS webinar last Thursday. Mr. Kirkland responded:

    “… we’ve engineered our products to use services that are available for payment to LightSquared’s predecessors. That’s a critical point…these precision receivers are designed to receive MSS signals to make the services better and they pay for those services to Skyterra (owned by LightSquared) and Inmarsat (LightSquared vendor). So if that’s a bad design decision that we decided to design our receivers so that our customers could pay money to Skyterra (LightSquared), that’s one of the more absurd things I’ve heard in this whole debate.”

     

    What he’s talking about is that OmniSTAR pays SkyTerra (LightSquared) to lease bandwidth on their satellite to deliver corrections to high-precision GPS users on the ground. Yes, if you pay OmniSTAR for their VBS, HP, or XP service, then a portion of what you pay goes to LightSquared. The irony is as thick as molasses. Furthermore, Deere & Co/Navcom offer a similar service called Starfire in which they lease satellite bandwidth from Inmarsat. LightSquared and Inmarsat are connected. Based on an original agreement signed in December 2007 between LightSquared’s predecessor and Inmarsat, Inmarsat is to receive hundreds of millions of dollars from LightSquared towards “the re-banding and efficient reuse of L-band radio spectrum covering North America.”

    Essentially, what LightSquared is doing is selling the GPS industry their satellite-to-earth wireless services (a la OmniSTAR), but they are complaining that the GPS industry has designed GPS receivers to utilize services in which LightSquared gets paid. Is that a “poorly designed GPS receiver”?

    I’ve even heard, through the grapevine, that some legislators are regurgitating this nonsense of “poorly designed GPS receivers.” Maybe there’s no ill-intent, but it’s either that or a fair amount of ignorance.

    Logically, many of today’s high-precision GPS receivers have OmniSTAR/Starfire capability built into their antennas and RF front-ends to look into the 1525-1559 Mhz spectrum for the OmniSTAR/Starfire signals. They don’t focus on particular frequencies in that band because the frequencies change periodically as OmniSTAR users can attest. Also, even if you have the OmniSTAR/Starfire capability turned off in your receiver, the antenna is still designed to look into that band so there’s no way around it.

    Like I mentioned earlier, even if your receiver isn’t designed to utilize OmniSTAR/Starfire, no one knows yet if it might be affected by the LightSquared 5L/10L signal.


    Where do we go from here?

    There’s a lot more to talk about on this issue. It’s as critical as it’s ever been that you make you concerns known to your state senators and representatives as well as the FCC. Scroll to the bottom of this article for web links and contact information.

     

    Free Webinar – Thursday, June 23. LightSquared: What it means to the GPS Surveying/Mapping User Community

    Thursday, June 23, I will conduct a webinar to discuss the LightSquared issue as it relates specifically to the GPS Surveying/Mapping community (high-precision users). Joining me will be Dr. Mike Whitehead, VP of Technology at Hemisphere GPS. He’s a leading GNSS design engineer and can speak clearly about the technical ramifications of LightSquared interference on high-precision GPS receivers. Click here to sign up for the webinar. Sign up even if you can’t attend the live webinar on Thursday because you’ll be sent an email on how to view the archived presentation that you can listen/view at your convenience.

     

    Light
    Squared coverage at the Esri Survey Summit (July 7-12, San Diego, CA)

    Esri has coordinated comprehensive coverage of the LightSquared issue at this years Survey Summit. Remember, this year the Survey Summit is combined with the ACSM (American Congress on Surveying and Mapping) annual conference so the turnout should be very good.

    On Friday, July 8th @ 2pm at the Survey Summit, I’ll be giving a 60 minute presentation entitled “GPS/GNSS Technology Update” focused on covering the latest developments in GPS/GNSS. I will cover the latest LightSquared news as well as other recent GPS/GNSS technology developments.

    On Saturday, July 9th @ 3:30p and 4:00p respectively, Jeffrey Carlisle from LightSquared and Peter Large from Trimble Navigation will give 30 minute presentations on the GPS/LightSquared interference issue.

    On Sunday, July 10th @ 8:00a-10:00a there will be a GPS/LightSquared discussion panel consisting of myself, Peter Large, Jeff Carlisle, Curt Sumner (ACSM), John Matonich (NSPS), and Dr. Javad Ashjaee. The panel discussion will be moderated by Joe Paiva. This will be the first panel discussion in the industry focused on the high-precision GPS/LightSquared interference issue.

    Following the discussion panel, at 10:30am-Noon,  there will be a strategy session designed to plan actions that surveyors (high-precision users) can take to avoid becoming collateral damage.

    ———————–

    Take Action Now
    The Coalition to Save Our GPS has posted guidance on its website as to how to submit your comments. They are:
    Voice your concerns directly to Congressional Representatives
    To voice your concerns about GPS interference, you can send letters, emails, faxes, call or visit your Congressional representatives’ office in person to explain how you use GPS as a local business and what the impacts of interference would be to the local economy.
    Contact Your Local Senator
    Ask your Senator to support and co-sign the letter from Senators Roberts (R-KS), Nelson (D-NE) and nearly a third of the U.S. Senate: explain how you use GPS in your state and what impact interference or any compromise of the GPS service would have on you and the local economy.
    Write Your Representative
    The Washngton Wire reported this week that “A bipartisan group of 66 House members asked the FCC Tuesday to protect global positioning systems from interference from wireless broadband start-up LightSquared…”
    Please include: “Coalition to Save Our GPS and FCC File No. SAT-MOD-20101118-00239” in your correspondence.
    Send your comments directly to the Federal Communications Commission (FCC)
    Email the FCC: [email protected]
    For your ready reference, below are the actions the Coalition is seeking from the FCC:
    1. The FCC must make clear, and the NTIA must ensure, that LightSquared’s license modification is contingent on the outcome of the mandated study unequivocally demonstrating that there is no interference to GPS. The study must be comprehensive, objective, and based on correct assumptions about existing GPS uses rather than theoretical possibilities. Given the substantial pre-existing investment in GPS systems and infrastructure, and the critical nature of GPS applications, the results of studies must conclusively demonstrate that there is no risk of interference. If there is conflicting evidence, doubts must be resolved against the LightSquared terrestrial system. The views of LightSquared, as an interested party, are entitled to no special weight in this process.
    2. The FCC should make clear that LightSquared and its investors are proceeding at their own risk in advance of the FCC’s assessment of the working group’s analysis. While this is the FCC’s established policy, the Commission’s International Bureau failed to make this explicit in its order.
    3. Resolution of interference has to be the obligation of LightSquared, not the extensive GPS user community of millions of citizens. LightSquared must bear the costs of preventing interference emanating from their devices, and if there is no way to prevent interference, it should not be permitted to operate. GPS users or providers should not have to bear any of the consequences of LightSquared’s actions.
    4. This is a matter of critical national interest. There must be a reasonable opportunity for public comment of at least 45 days on the report produced by the working group and further FCC actions on the LightSquared modification order should take place with the approval of a majority of the commissioners, not at the bureau level.
    Thanks, and see you next time.
    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

  • LightSquared: It’s Worse than You Think

    Tired of hearing about LightSquared? Think it’s a bunch of panicking journalists hungry for something to write about? Listen, it usually takes a lot to get the hairs standing up on the back of my neck. On the LightSquared issue, they are at full attention.

    Why?

    The GPS receivers that would likely be affected the most aren’t military, automobile, aviation, mobile phones, etc. The GPS receivers that would be affected the most are the ones you use, the high-precision GPS receiver!

    This means any receiver designed to produce accuracies at meter-level or better (submeter, decimeter, centimeter receivers). This means surveying, engineering, construction, bridge/dam/structure/seismic monitoring, GIS, precision agriculture, mining, utilities/telecom, transportation, environmental, disaster management, and all sorts of machine control across a vast number of industries.

    Do the Math

    LightSquared is planning to construct 40,000 ground-based transmitters broadcasting 1,500W each across the U.S. These are targeted at metropolitan areas with high-density population. The will pop-up like mobile phone towers. What do you think a map looks like with 40,000 LightSquared transmitters overlaid on the current infrastructure of CORS (1,500+ GPS receivers in the U.S.) and RTK networks (100+ consisting of several thousands of receivers in the U.S.)?

    Do you use OPUS? Do you use CORS? Do you use an RTK network? Do you use WAAS corrections? Do you use OmniSTAR? Do you use StarFire? Do you operate your own high-precision base station (real-time or post-processing)? I do not know one high-precision user who does not use one of the aforementioned technologies in their GPS operations. All of the above technologies are in jeopardy.

    I’m going to keep this simple. You, the high-precision GPS user, are likely going to be considered collateral damage.

    The military is going to be accommodated in the name of national security. The aviation industry is going to be accommodated in the name of safety-of-life. The auto navigation industry is going to be accommodated because they are high-profile. The high-precision user is going to be thrown under the bus because we are the most difficult to accommodate (technically) and don’t have a high profile nor are perceived as significant enough to accommodate.

    In other words, the high-precision user will be told to “deal with it.”

    What Does “Deal with It” Mean?

    It’s not clear at this point, but without any hardware modification, your receiver performance will likely be degraded (weakened or lost signal) in metropolitan areas, and to a lesser extent in rural areas. That totally depends on where LightSquared decides to place its towers. Very soon, with the final Working Group report due to the FCC (June 15), we will see how serious the interference will be.

    GPS receiver manufacturers would likely offer some sort of hardware upgrade, if possible. You can bet that they won’t support upgrading older hardware and it’s possible some newer hardware won’t be retrofittable, so the upgrade turns into a “trade-in” with a hefty price tag. But beware that a hardware upgrade doesn’t mean it will solve the problem, but rather minimize it.

    In order to have a chance of not being forgotten or dismissed as collateral damage, you need to jump loudly and with resolution to raise awareness with your congressperson and the FCC about the importance of GPS to your operations. If you’re an international user, write the FCC.

    You can view the list of submissions made to the FCC by clicking here. Deere & Co. as well as Fugro and many others provided very clear and concise comments.

    The Coalition to Save Our GPS has posted guidance on its website as to how to submit your comments. They are:

    Voice your concerns directly to Congressional Representatives

    To voice your concerns about GPS interference, you can send letters, emails, faxes, call or visit your Congressional representatives’ office in person to explain how you use GPS as a local business and what the impacts of interference would be to the local economy.

    Contact Your Local Senator

    Ask your Senator to support and co-sign the attached letter from Senators Roberts (R-KS) and Nelson (D-NE): explain how you use GPS in your state and what impact interference or any compromise of the GPS service would have on you and the local economy.

    United States Senate Letter from Pat Roberts (R-KS) and Ben Nelson (D-NE)

    Find Your Local Senator

    Write Your Representative

    Find Your U.S. House of Representatives

    Please include: “Coalition to Save Our GPS and FCC File No. SAT-MOD-20101118-00239” in your correspondence.

    Send your comments directly to the Federal Communications Commission (FCC)

    Email the FCC: [email protected]

    For your ready reference, below are the actions the Coalition is seeking from the FCC:

    1. The FCC must make clear, and the NTIA must ensure, that LightSquared’s license modification is contingent on the outcome of the mandated study unequivocally demonstrating that there is no interference to GPS. The study must be comprehensive, objective, and based on correct assumptions about existing GPS uses rather than theoretical possibilities. Given the substantial pre-existing investment in GPS systems and infrastructure, and the critical nature of GPS applications, the results of studies must conclusively demonstrate that there is no risk of interference. If there is conflicting evidence, doubts must be resolved against the LightSquared terrestrial system. The views of LightSquared, as an interested party, are entitled to no special weight in this process.
    2. The FCC should make clear that LightSquared and its investors are proceeding at their own risk in advance of the FCC’s assessment of the working group’s analysis. While this is the FCC’s established policy, the Commission’s International Bureau failed to make this explicit in its order.
    3. Resolution of interference has to be the obligation of LightSquared, not the extensive GPS user community of millions of citizens. LightSquared must bear the costs of preventing interference emanating from their devices, and if there is no way to prevent interference, it should not be permitted to operate. GPS users or providers should not have to bear any of the consequences of LightSquared’s actions.
    4. This is a matter of critical national interest. There must be a reasonable opportunity for public comment of at least 45 days on the report produced by the working group and further FCC actions on the LightSquared modification order should take place with the approval of a majority of the commissioners, not at the bureau level.

     

    Lastly, following is the list of high-precision GPS receivers that the Working Group (consisting of US GPS Industry Council representatives and LightSquared representatives) have chosen to test:

    Hemisphere R320 (with A52 antenna)
    Hemisphere A320 (with Integral antenna)
    Deere iTC (with Integral antenna)
    Deere SF‐3000 (with Integral antenna)
    Deere SF‐3050 (with Aero antenn
    a)
    Trimble MS990
    Trimble MS992
    Trimble AgGPS 252
    Trimble AgGPS 262
    Trimble AgGPS 442
    Trimble AgGPS EZguide 500
    Trimble CFX 750
    Trimble FMX
    Trimble GeoExplorer 3000 series GeoXH
    Trimble GeoExplorer 3000 series GeoXT
    Trimble GeoExplorer 6000 series GeoXH
    Trimble GeoExplorer 6000 series GeoXT
    Trimble Juno SB
    Trimble NetR9 (with Zephyr 1 antenna)
    Trimble NetR9 (with Zephyr 2 antenna)
    Trimble R8 GNSS (with Integral antenna)
    Trimble 5800 (with Integral antenna)
    Trimble NetR5 (with Zephyr 1 antenna)
    Trimble NetR5 (with Zephyr 2 antenna)
    Leica SR530 (with AT502 antenna)
    Leica GX1200 Classic (with AX1202 antenna)
    Leica GX1230GG (with AX1202GG antenna)
    Leica GR10 (with AR10 antenna)
    Leica Uno (with GS05 antenna)
    Leica GS15 (with Intergral antenna)
    Topcon HiPer Ga
    Topcon HiPer II
    Topcon GR‐3 (with Integral (5/8) antenna)
    Topcon GR‐5 (with Integral (5/8) antenna)
    Topcon MC‐R3 (with MC‐A3/cabled (5/8) antenna)
    Topcon NET‐G3A (with CR‐G3/cabled (5/8) antenna)
    Topcon TruPath/AGI‐3 (with Integral (special mount) antenna)
    NovAtel PROPAK‐G2‐Plus (with GPS‐702/GPS‐701 antenna)
    NovAtel FLEXG2‐STAR (with GPS‐701GGL/GPS‐701 antenna)
    NovAtel FLEXPAK‐G2‐V1 (with GPS‐701GGL/GPS‐702 antenna)
    NovAtel FLEXPAK‐G2‐V2 (with GPS‐702GGL/GPS‐702 antenna)
    NovAtel PROPAK‐V3 (with GPS‐702GGL/GPS‐702 antenna)
    NovAtel DL‐V3
    NovAtel FLEXPAK6 (with GPS‐702GGL/GPS‐702 antenna)
    Septentri PolaRx3e (with PolaNt GG antenna)
    Septentrio AsteRx3 (with PolaNt G antenna)

     

    Thanks, and see you next time.

    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

     

     

     

     

     

  • Q&A from L5 and LightSquared Webinars

    In late March, I conducted a webinar titled “A Closer Look at L5: The Future of High-Precision GNSS,” in which I discussed the impact that the new GPS L5 signal/frequency may have on high-precision users. Then, in April I was part of a discussion panel-format webinar titled “LightSquared: Our Story So Far.” Many questions and comments arose from both webinars, and I’ll attempt to address those in this column.

    First of all, the day after the March 17 webinar, I published a summary with some links and illustrations. If you want to review it to refresh your memory or get a quick overview if you didn’t attend the webinar, click here.

    During the March 17 webinar, I conducted several polls. Following are the poll questions with accompanying pie charts to illustrate the results. I think polls are a great tool to gain a better understanding of what your colleagues are thinking.

    Poll #1: Does your organization use dual frequency GPS (L1/L2) receivers?

    Gakstatter comment: Nothing earth-shattering, but good to know most of the audience members polled are high-precision users.

    Poll #2: When do you plan on upgrading your GPS receivers to take advantage of the new L2C and L5 signals?

    Gakstatter comment: I think the large number of “I don’t know” answers is due to two major variables. #1 is the economy. If the economy was healthy, I think folks would be more inclined to take the risk upgrade to the latest technology. #2 is the unclear status of GPS and Galileo (and other GNSS). If there was a launch schedule that people knew they could count on and plan for, I think users would be more inclined to upgrade sooner rather than later.
    Poll #3: Do you believe that GPS and Galileo will meet their projected deployment dates of 2014/2015?
    Gakstatter comment: I understand the skepticism about GPS and Galileo staying on schedule. I don’t think the GPS schedule can push out too far because the FAA requires a full constellation of GPS satellites broadcasting L5 by 2019. The Galileo program is under a lot of pressure to deliver something to the user community. A very important milestone this year is the scheduled September launch of the first two operational Galileo satellites, followed by the launch of a second pair the first quarter of next year. This is an opportunity for the Galileo program to set a new tone and sense of urgency with the user community.
    Poll #4: How concerned are you that LightSquared’s initiative might interfere with your GPS operations?
    Gakstatter comment: Since the March 17 webinar, there’s been much more information released and published about LightSquared’s potential effect on GPS. In April, I participated in a webinar about LightSquared’s potential effect on GPS with my portion of the webinar specifically addressing high-precision users. I will discuss this later in this article. But, suffice to say that this is a serious issue for the U.S. high-precision GPS user community. LightSquared isn’t going to walk away from this without putting up a big fight, and they have enough of an argument that I could see the FCC (Federal Communications Commission) folding or trying to negotiate a compromise. However, any compromise is likely to have a negative effect on the high-precision GPS user community. Best case scenario, there would be a hit in signal strength. Worst case, you’ll need a hardware upgrade.
    As I normally do, a number of questions were raised during the webinar and I will address them here to the best of my ability. I’ll start with the L5 questions and then address some of the questions regarding LightSquared that were asked from both the March and April webinar.

    On to the Questions

    Question #1: What impact will L5 have on RTK networks?

    Gakstatter comment: Great question. There’s only upside in having another GPS frequency to work with. Since the premise behind RTK Networks relies heavily on atmospheric modeling, L5 is going to help. It’s further separated, with respect to frequency, from L1 than L2 and the signal is much stronger than L2. L5 will go a long way in mitigating the effects of the atmosphere on high-precision GPS positioning.

    They logistics of implementing L5, by the manufacturers, into RTK Networks may not be so easy. I’m not sure that L5 has been defined well enough in the RTCM specifications and even if it was, I’m not sure how fast manufacturers would implement it. Take, for example, L2C. Even though there are eight satellites broadcasting L2C, I’m not sure there are any RTK Networks taking advantage of it and transparency between different rover manufacturers. However, my gut tells me that manufacturers will be more willing to jump on the L5 bandwagon with a sense of urgency due to the potential significant increase in receiver performance.

    Question #2: What could be a better frequency combination in terms of acheiving higher sensitivities: L2C/L5 or L1/L5?

    Gakstatter comment: This is another great question. Technically speaking, I’m guessing that L2C/L5 would be a higher-performing combination due to the significantly-improved code structure of L2C (longer code and improved error-correcting methods), which allows
    the signal to be acquired and tracked better in tough GPS conditions such as under tree foliage.

    Question #3: If I toggle on L2C in my current Trimble GNSS; that would give me an extra 8 SV broadcasting

    Gakstatter comment: Good, creative thinking, but it doesn’t work that way. You are already using those eight satellites with L1 C/A and L2P. If you utilize L2C from those satellites, you’ll get some marginal gain in performance (assuming the reference station is broadcasting L2C info), but nothing like adding eight additional satellites.
    Question #4: What accuracy can be expected from single frequency L5?

    Gakstatter comment: It’s going to be better than L1 C/A due to the stronger signal strength (4 x more powerful than L2C) and much longer code structure (than even L2C). With SBAS corrections, we’re seeing about 60cm now with L1 C/A. It will probably be slightly better than that and definitely more robust positioning in marginal GPS conditions.

    Question #5: What sort of base line distances can we expect to get with L5?

    Gakstatter comment: Using L5 will definitely help with longer baselines, but baselines are already pretty long. Look at the distance between reference stations in RTK Networks today. Some are pushing 70-80km. Will they go longer than 100km? I’m not sure. That would be cool, lowering infrastructure costs of setting up and operating RTK Networks.

    Question #6: Using RTK corrections the bandwidth requirements will increase with all these extra satellites will there be more efficient correction broadcast techniques like CMRx?

    Gakstatter comment: I agree. I think there will need to be an efficient way of getting the data from reference network to rover. That either means using up more bandwidth on your mobile phone data plan (if you aren’t using UHF/VHF/Spread spectrum radios) or manufacturer’s inventing more efficient formats. 

    Questions Regarding LightSquared

     

    LS Question #1: LightSquared is going to filter their signal heavily until it will not interfere. They have too much invested to fail.

    Gakstatter comment: I agree that LightSquared is not going to walk away from their huge investment. But even if they heavily filter the base transmitters (40,000 of them), I still think there will be some interference. The nature of high-precision GNSS receivers is that they have a wideband RF front-end to take into account better code tracking and accomodate other signals such as OmniSTAR and Starfire. 
    Also, since LightSquared can’t control the design/production of the mobile phones that will use their system, each of the mobile phones can potentially be a “mobile GPS jammer”. It’s one thing to know the fixed location of each of the 40,000 transmitters, but how about the tens of thousand, hundreds of thousands or millions of mobile phones using the LightSquared infrastructure.

    LS Question #2: What do you see as the future for OmniSTAR?

    Gakstatter comment: Obviously, OmniSTAR and Starfire people must have major concerns since they are well within the LightSquared frequency spectrum. Ironically, OmniSTAR currently leases satellite bandwidth from LightSquared to broadcast their corrections.

    I’m sure they are working on a solution, but I’m not privy to what the options they are considering.

    Another option is another delivery method such as NTRIP over mobile phone networks.

    LS Question #3: If the signal effects high precision users, it will also effect casual users(hunters, fishermen, and also field technicians – forestry inventory and utility asset mapping – will w ALL need to change the GPS devises currently used today?

    Gakstatter comment: It won’t affect casual users as much as high-precision users due to the inherent design of the receivers. But, you’re right about forest inventory, utility mapping, etc. which typically use high-precision receivers. If LightSquared is allowed to continue on their desired path, it’s possible that each high-precision receiver would need to be upgraded (or traded in). That’s the worst-case scenario.

    LS Question #4: Would better filters on the GPS receiver front-ends improve the concerns?

    Gakstatter comment: Yes, but it’s not clear if high-precision receivers would perform as well with such filters designed into the receiver.

     

    LS Question #5: Is the transmitter the cell phone or Lightsquare base station?

    Gakstatter comment: This is a bit outside of my area, but both are transmitters. The LightSquared base stations are designed to broadcast at 1,500 watts while the mobile phone’s highest transmission power is probably 1-3 watts while it’s first connecting to the network. The base stations are transmitting at the band adjacent to GPS on the lower end while the mobile phones transmit in the adjacent band above the GPS. I look forward to reviewing the data in the next working group report to the FCC which includes interference testing from both base station transmitters as well as mobile phones.

    LS Quest
    ion #6:     How does LightSquared affect L2C, if at all?

    Gakstatter comment: From what I know and have read, I don’t think it would have any direct affect on L2 since L2 is at 1227MHz, far from LightSquared’s frequency spectrum of 1525MHz to 1559MHz. Indirectly, it would have an affect on L2P as L1/L2 receivers need L1 to utilize L2P. That’s not the case with L2C, but remember there are only eight satellites broadcasting L2C at this time.

    Obviously, there is more to discuss. I didn’t touch on the affect on GLONASS receivers (yes, there is a potential problem too). The feedback I received from the LightSquared webinar is that many of you would like to have a webinar that is focused on LightSquared as it relates to the high-precision user (surveying, mapping, engineering, GIS, etc.). I plan to conduct such a webinar in early June. Stayed tuned for the announcement. Hopefully, I’ll have some interesting new data to present from the report due to the FCC on May 15.

    Lastly, I attended NOAA’s Space Weather Workshop last week in Boulder, Colorado. I plan on a more comprehensive write-up, but in the mean-time you can check out my Geospatial Solutions Weekly newsletter with some info on my visit there. I’m still working on a GPS space weather notification system I wrote about last summer. I’m getting closer to having something for you.

    Thanks, and see you next time.

    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

  • GPS Surveying/Mapping Current Events

    Trimble Navigation has made a fair number of strategic acquisitions in the past ten years. Spectra-Precision and Tripod Data Systems were acquired early last decade. Applanix, Seco Manufacturing are some you’ve heard of, but there’s been a fair number of companies that you’ve never heard of, typically ones that allow Trimble to entrench themselves deeper into their core vertical markets (engineering, construction, GIS, MRM, etc.). Trimble has always strived at providing a complete solution (hardware, software, sensors, etc.) and it’s one of the reasons they’ve been so successful.

    Within the past 30 days, they announced two acquisitions that are higher profile and you may have noticed.

    The first acquisition was Measurement Devices, a UK-based company specializing in laser rangefinders. The acquisition is not surprising as the ground-based (terrestrial) laser scanning business is growing. Actually, I should clarify, I’m not sure it was an acquisition or what kind of acquisition it was since there’s been no press announcement on it that I’ve seen, but it doesn’t matter. Obviously, something happened because this week Trimble announced the Trimble LaserAce 1000 handheld laser rangefinder, which is clearly based on MDL technology.

    Trimble LaserAce 1000

    The second acquisition was a bit more surprising to me and some of you, but probably a smart move on Trimble’s part. Trimble announced they acquired certain assets of OmniSTAR’s land applications business. OmniSTAR also has a significant offshore client base (oil & gas) so apparently that wasn’t included in the sale. The acquisition does include OmniSTAR’s land business for North/South America, Europe/North Africa/Middle East/India, Asia Pacific, and South Africa.

    The OmniSTAR acquisition is pretty smart, at least for the medium-term. Trimble has been quietly (until now) growing their GPS correction service business. Their VRS Now service, a subscription-based RTK Network, provides both RTK and decimeter corrections in many parts of the world already. OmniSTAR will only enhance Trimble’s subscription offering. In the short-term, they will have a strong portfolio in the real-time corrections business with Deere/Navcom being the only other major player offering satellite-based world-wide subscription services. However, the Deere/Navcom system (StarFire) is focus on agriculture and doesn’t have much support from receiver manufacturers/integrators outside of the agriculture market like OmniSTAR does. With Trimble’s acquisition of OmniSTAR’s land business, Deere/Navcom might look at the non-ag markets differently. It will be interesting to watch.

    The longer-term competition for real-time decimeter correction are the public (free) SBAS such as WAAS (North America), EGNOS(Western Europe/No Africa), MSAS (Japan), and GAGAN (India). They are all slated to implement the new civil L5 signal. Once that happens, albeit 5-10 years from now, decimeter accuracy will be at your fingertips, free of charge, if you’re using an L1/L5 capable receiver and in an SBAS coverage area.

    Speaking of Deere/Navcom, just this week they showed signs of non-agriculture life by taking a step to enter markets outside of agriculture with the introduction of their pole-mount SF-3040 GNSS receiver. Although somewhat of a “me too” product, it does include the capability of accessing their StarFire network, which makes it unique.

    Deere/Navcom’s SF-3040 Pole-Mount GNSS Receiver

     

    Seeing how OmniSTAR seems to be a popular subject this week, newcomer Geneq added another OmniSTAR receiver to their product like this week. Claiming to be the smallest GPS L1/L2 OmniSTAR receiver in the world, they introduced the SXBlue III-L GPS that’s able to use OmniSTAR’s HP and XP corrections services. If you recall, a few months ago, Mike Whitehead and I collected 24 hrs. of OmniSTAR HP-corrected data as part of some experimenting we did for the January webinar. I ran the data through a rigorous statistical software program that randomly tested the accuracy of the data. The horizontal accuracy (at the NSSDA 95% confidence level) was 9cm.

    Geneq SXBlue III-L GPS

     

    LightSquared Saga

    I feel I need to keep you up-to-date on what’s going on with LightSquared. As crazy as it sounds, I could see the FCC pushing this through unless the GPS community makes a lot of noise. Bear in mind, I don’t think it’s an ‘all or nothing” deal. LightSquared is not going to rollover. For sure, the testing will show it jams GPS to some extent. I’m confident of that. At the end of the day, I think they will push for some sort of compromise, a compromise that would likely mean that GPS functionality would be degraded, possibly signal strength degradation. The high-precision users (sub-meter and below) will take the hit because those receivers try to squeeze as much from GPS as possible, so a few dB of signal strength is very important.

    On April 21, we are hosting a free webinar entitled “LightSquared and GPS: Our Story So Far”. I’ll be on the webinar dicussion panel as well as some people who are a lot more intelligent than me. My role is to bring a high-precision user community perspective to the discussion. If you want to gear up on the LightSquared issue, the webinar is a good opportunity.

    To help visualize the issue, following is a graphic I lifted from the Federal Communications Commission (FCC) website. I’ve inserted the GPS center frequencies (L1, L2, L5) as well as frequencies that LightSquared wants to use. If radios worked with nice, clean lines, we’d be in good shape. LightSquared would stay below 1559 MHz and GPS would stay above 1559 MHz. But it doesn’t work that way. High-precision GPS receivers use a wide radio front-end for improved performance. It can be as much as 25 MHz wide. 1575 MHz (GPS L1 center frequency) minus 25 MHz = 1550 MHz. LightSquared base stations are broadcasting at 1,500 watts. A certain amount of noise is going to invade the 1559-1610 MHz range that GPS uses. Furthermore, mobile devices built to use LightSquared’s signal may also invade the 1559-1610 MHz range. The water starts to become muddy very quickly. Bear that in mind when viewing the chart below.

     

    Source: FCC

     

    Click here
    to view the latest article from GPS World on LigthtSquared and GPS.

    Lastly, it’s not too late to take action. Following is a response I received from Oregon U.S. Senator Jeff Merkley after contacting his office about my concerns.

    I haven’t heard anything more since I received this letter on March 25, 2011, but I trust Mr. Merkley’s staff is querying the FCC about this. The more attention we draw to the issue, the better.

    Thanks, and see you next time.

    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

     

  • Webinar Brief – A Closer Look at L5: The Future of High-Precision GNSS

    Yesterday I conducted a webinar titled “A Closer Look at L5: The Future of High-Precision GNSS.” Preparing for it was quite interesting, so I thought I’d share some of the slides I produced (and had produced) for the webinar. I think you’ll find them interesting.

    The webinar was focused on discussing the value of the new L5 civilan frequency for GPS/GNSS receivers. An interesting challenge in preparing for the webinar was my attempt at estimating what a satellite constellation of satellites (GPS and others) broadcasting at least L1 and L5 would look like four or five years from now. The point of it was to illustrate that a useful constellation of satellites broadcasting L1 and L5 (as well as L2C) is potentially only four to five years away.

    In that timeframe, there are potentially 30 satellites that would be healthy and broadcasting navigation signals on the L1 and L5 frequencies that we can use. How is that possible?

    Both GPS and Europe’s Galileo support the new L5 civil frequency (as well as L1). The U.S. has already launched one of the new GPS model IIF satellites. The IIF is currently healthy and broadcasting three civil frequencies; L1 C/A, L2C and L5. There are 11 more of the IIF satellites being built. It’s estimated that all 11 will have been launched into their orbits by ~2015. On the other hand, the first 18 Galileo satellites have been contracted to be built, and it’s estimated that the 18 will be launched into their orbits by ~2015. The Galileo satellites are designed to support L1 and L5 (as well as others). That’s a total of 30 satellites broadcasting L1 and L5.

    In an ideal world and in the best interest of the civilian user community, the Americans and Europeans would coordinate orbits planes/slots of the 30 satellites so they would be in an optimal configuration (steady # of visible satellites, reasonable PDOP) for the user community. But, I seriously doubt that’s going to happen.

    So, the next best thing is to attempt to estimate what an “uncoordinated” constellation of 30 GPS/Galileo satellites would look like in 2015 (assuming the launch schedules hold). Fortunately, our friends at the Galileo Supervisory Authority (GSA) have already mapped out the orbit plane/slot data for the 18 satellites. Without that data, none of these projections would have been possible.

    GPS was a little tougher to estimate. The U.S. Air Force doesn’t have (or at least they don’t share) a long-range plan for where the next 11 IIF satellites are going to be inserted in the GPS constellation. They look out one satellite at a time. That’s understandable because the health of the GPS constellation changes over time. However, the U.S. Air Force does present a “watch list” of the weaker satellites in the constellation so we have some idea of where the new ones are going to be placed.

    Once we compiled the information from the Galileo folks and our projections on where the next 11 IIF GPS satellites will be inserted, we were able to come up with some interesting plots I’d like to share with you.

    All of the following satellite visibility plots are based on my location in Portland, Oregon, USA, and with a 15º elevation mask. Using a 15º elevation mask is pretty conservative so the plots are pretty conservative if you’re working in an open-sky environment like in agriculture.

    The first plot is of the 12 GPS IIF satellites only. You can see there’s an average of about three IIF satellites in view between 6 a.m. and 8 p.m. Thanks to Analytical Graphics, Inc. for help generate the following plots.

     

     

    The next plot is of the 18 Galileo satellites. You can see there’s an average of 4-5 Galileo satellites in view between 6 a.m. and 8 p.m.

     

     

    The next plot is of both the 12 GPS IIF satellites and the 18 Galileo satellites. You can see there’s an average of 8 GPS IIF and Galileo satellites in view between 6 a.m. and 8 p.m.

     

     

    Finally, the last plot is of the 12 GPS IIF satellites, 18 Galileo satellites, and the 19 remaining legacy GPS satellites (broadcasting L1 and L2). You can see there’s an average of 12 GPS IIF, Galileo, and legacy GPS satellites in view between 6 a.m. and 8 p.m.

     

    For a different perspective, here are 3D orbit plots of the 18 Galileo satellites and the 12 GPS IIF satellites.

    3D orbit plot of 18 Galileo satellites

     

    3D orbit plot of 12 GPS IIF satellites

    There are several more plots similar to these in my webinar for different locations around the world including London, Rio de Janeiro, New Dehli, Perth, and Bangkok. In the webinar presentation, I also provide more details about the benefits of L5. You can view a recording of the webinar by registering here. After registering, you’ll receive an e-mail with instructions on how to view the webinar.

    Thanks, and see you next time.

    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

  • I’m Buying A New RTK Receiver. What Should I get?

    In light of this weeks webinar, A Closer Look at L5: The Future of High-Precision GNSS, and spurred by an email from a reader about how to sift through all the GPS/GNSS receiver choices, following are my thoughts if you’re looking to purchase an RTK receiver today.

    First of all, an email from a reader succinctly sums up the challenge:

    I currently utilize static GPS / GLONASS receivers in my day to day operations and I am looking at buying a couple more receivers (an RTK setup). To be honest, I am totally confused as to what technology I should buy.
    Specifically, I don’t know whether or not it is worth buying receivers that have L2C and L5 capabilities. It seems that vendors are not very well educated on what these options can do for you, and how many satellites are up and running that provide these signals. It is my understanding that L2C is simply a civilian code that is carried on the L2 frequency, and that it provides an almanac and atmospheric correction information. I don’t even know if receiving L2C will help me as a surveyor, or if it is more designed for autonomous use in navigation. It sounds like L5 will be of great advantage once the constellation has enough SVs that broadcast it.  It also seems like Galileo will be extremely helpful for surveyors, but who knows when that will be available. Basically, I don’t want to spend thousands of extra dollars for “bells and whistles” that are not yet operational from a practical standpoint, and that won’t be in the near future.

     

    He’s right. There are a lot of moving parts these days in the world of GPS/GNSS. Not only are GPS/GNSS receivers steadily improving (better, smaller, faster, cheaper), but the GNSS themselves (GPS, GLONASS, SBAS) are changing too. Making a decision of which “bells and whistles” to pay for and which ones to pass up is not so easy.

    Let’s break it down and see if we can clear things up.

    It used to be that when looking to purchase a dual frequency GPS receiver, the choice was simple because RTK receivers came in one flavor, L1/L2.

    Do I want RTK (real-time centimeter positioning) or am I satisfied with post-processing the GPS data?

    Either way you went, it was an straight-forward decision.

    Today, that is not the case. If you choose RTK, there are many options available:

    -GPS L1 or GPS L1/L2?

    -add GLONASS?

    -add L2C?

    -add L5?

    -add Galileo?

    The pricing of these options can be substantial. The reader’s letter goes on…

     

    I have a vendor that is pushing an L2C capable receiver on me for more money than a standard dual frequency dual constellation receiver.  The other option is to spend about $13K more and get the L2C, L5, and Galileo ready receiver.

    If you look at what the manufacturer’s are offering for GPS/GNSS RTK receivers, it seems there are generally four choices:

    1. GPS L1

    2. GPS L1/L2

    3. GPS L1/L2 + GLONASS

    4. GPS L1/L2 + GLONASS + L2C + L5 + Galileo

     

    GPS L1

    longer initialization (issue when working around trees)

    short baseline length

    Really should have the same base/rover receiver (SBAS), not really suited for RTK Network usage.

     

    GPS L1/L2

    Legacy, proven technology.

    Upside…less expensive, entry level dual frequency RTK

    Downside…GPS “brownouts”, susecptible to semi-codeless sunset

     

    GPS L1/L2 + GLONASS

    Eliminates the GPS “brownout” problem.

    Increased cost, although some manufacturers include it.

    Doesn’t support future signals

    Suscpetible to semi-codeless sunset.

     

    GPS L1/L2 + GLONASS + L2C + L5 + Galileo

    Eliminates the GPS “brownout” problem.

    Ready for future signals

    downside…future singals aren’t available yet.

    Increased cost

     

  • LightSquared Saga, and Recent Solar Activity

    This week I’m following up on my article from a couple of weeks ago about the potential effects of LightSquared’s plans. As a user of high-precision GPS receivers (particularly GPS L1 sub-meter, but also dual-frequency), you should be particularly concerned about this issue. I’ll tell you why. Also, I have a note on recent the solar activity.

    LightSquared

    The reasons you should be concerned about LightSquared’s plans are two-fold:

    1. Consumer GPS receivers and professional-grade GPS receivers designed for higher performance (mapping, surveying, etc.) aren’t necessarily designed the same way. High-performance GPS receivers use a wider bandwidth radio design.

    For example, the GPS L1 frequency is 1575.42 MHz. Many high-performance GPS receivers use a wide bandwidth radio that scans +/- 20 MHz from 1575.42 MHz. That equates to a range of 1555 MHz to 1595 MHz. LightSquared’s frequency spectrum is 1525 MHz to 1559 MHz. Clearly, there’s overlap, which is another word for interference. On top of that, LightSquared plans on a broadcast strength of 1,500 watts from a tower located down the street. The GPS broadcast signal strength is about 30 watts from a satellite located some 19,000 kilometers away in outer space. Who’s going to win that battle?

    I’m not an aerospace engineer or an RF (radiofrequency) engineer, but I don’t think it takes one to see the potential impact of LightSquared’s service on high-performance GPS receivers. At the very least, it warrants an in-depth technical study.

     

    2. Neither the policymakers nor LightSquared know about or understand the user community of high-performance GPS receivers comprised of hundreds of thousands of high-end GPS receivers. They think the GPS user community is comprised of auto navigation and mobile-phone users. They don’t understand that we are the infrastructure people. We use GPS in a way that they don’t understand, but is so critical to our infrastructure. It’s not their fault, but you can’t assume they know, so it’s up to us to inform them. You have to speak up.

    Here’s a perfect example. Click on the following link to view a report presented by LightSquared last week in Taipei, Taiwan, at a 3GPP conference.

    “Final Report on Overload Characteristics of GPS Receivers in Proximity to LightSquared’s L-band Terrestrial Base Stations (BTS) and User Equipment (UE)”

    The best part about this report is the following statement from the Executive Summary:

    “Although results have been provided to date of a limited number of devices (6), LightSquared proposes to close the study at this stage as a more comprehensive study, covering a wider variety of GPS receivers than those involved in cellular applications, has now been initiated under the auspices of the FCC [2].  This study will be conducted by a cross-industry group led by LightSquared and USGPSIC, the reports of the study having complete public visibility.”

     

    Granted, I understand the Taipei conference was focused on the impact of LightSquared’s plan on mobile phones using GPS, but if this is the extent of their testing, it’s alarming. Furthermore, it’s relatively easy to acquire and operate an inexpensive consumer GPS receiver. Can you picture LightSquared attempting to test a sub-meter GPS L1 receiver or a RTK setup? GPS, GLONASS, SBAS, DGPS, real-time, post-processing, and the myriad of receivers on the market need to be tested. Although it’s likely not possible to test all equipment on the market, it’s not prudent to leave anything to chance. If, one year from now, you wake up and find out your $10,000 RTK receiver doesn’t work like it used to, it will be too late to do much about it. It takes very little time to voice your concern now to your elected officials so the appropriate attention is given to high-precision users.

    The good news is that Trimble Navigation is involved, along with the Federal Aviation Administration, with the U.S. GPS Industry Council and will be working closely with LightSquared in a Technical Working Group to better understand the impact that LightSquared’s system would have on GPS. Trimble and the FAA aren’t the only parties involved in the working group, but they are the parties that understand the needs of the high-precision user.

    The Technical Working Group’s first report is due March 15, 2011. Time is short, so don’t delay.

    Use these guidelines to take action. It is a call to action from Dr. Joe Paiva, veteran of surveying since the 1980s with whom many of you are familiar.

     

    Solar Activity

    As you’ve probably heard, we’re entering the next solar cycle, which is due to peak in May 2013.
    I want to periodically touch on this subject as the solar activity is going to increase over the next few years, and if the solar activity (geomagnetic storms, not sunspots) is severe enough, it will have an effect on GPS accuracy and tracking. Regardless of what you’ve heard in the mainstream media in recent months, the last event serious enough to affect GPS operations was in December 2006. That’s not to say that things aren’t heating up.
    But the recent activity does highlight the fact that “the Sun has become, somewhat suddenly, more eruptive,” according to Joe Kunches, of NOAA’s Space Weather Prediction Center. “We’ve been fortunate so far, in that the terrestrial effects — and impacts to GPS — have been very minimal. The most obvious sign of this has been the brilliant auroras up north.”
    “The video shows a large prominence eruption — billions of tons of plasma being strewn off the Sun. Some of it is drawn by gravity and rains back to the surface — the rest of it escapes. It’s the blown-away plasma that forms the coronal mass ejections that, when properly pointed, go by the Earth and cause problems for GPS,” said Kunches.
    Click on the following image to view a 15-second video of a solar flare that occured on February 24, 2011.
    Credit: NASA/GSFC/SDO

    From NASA:

    When a rather large-sized (M 3.6 class) flare occurred near the edge of the Sun, it blew out a gorgeous, waving mass of erupting plasma that swirled and twisted over a 90-minute period (Feb. 24, 2011). This event was captured in extreme ultraviolet light by NASA’s Solar Dynamics Observatory spacecraft . Some of the material blew out into space and other portions fell back to the surface. Because SDO images are super-HD, we can zoom in on the action and still see exquisite details. And using a cadence of a frame taken every 24 seconds, the sense of motion is, by all appearances, seamless. Sit back and enjoy the jaw-droppi
    ng solar show.

     

    March 17, 2011 Webinar: A Closer Look at L5: The Future of High-Precision GNSS

    Last year, the first GPS IIF satellite was launched. It became the first GPS satellite to broadcast the new L5 civilian signal/frequency. At 1176 MHz, it is further separated from L1 and L2 and located in the protected Aeronautical Radionavigation Services band, so there is no possibility of commercial interference like we see today with the LightSquared controversy. The availability of GPS L5 will usher in a new era of inexpensive, accurate GNSS receivers and will be the future of high-precision GNSS receivers, and quite possibly single-frequency receivers. I will also discuss the international support of L5 from other GNSS in development such as Galileo, Compass, QZSS, as well as SBAS (WAAS/EGNOS/MSAS).

    I’ll be presenting some interesting new material in the webinar such as graphics illustrating how many satellites (GPS and others) are projected to be broadcasting L1 and L5 just four years from now. It will be well worth 60 minutes of your time.

     

    Thanks, and see you next time.

    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

     

  • Webinar Follow-up Q&A: SBAS, DGPS or Post-Processing? Which Should You Use?

    Last week, I conducted a webinar along with Dr. Michael Whitehead titled “SBAS, DGPS or Post-processing? Which Should You Use?” It was one of the best webinars I’ve conducted to date. More than 600 people registered. We barely squeezed it into 65 minutes and could have kept going for the better part of two to three hours, given the subject matter to cover and the number of questions we received before and during the webinar. Thank you for attending, if you did. If you weren’t able to you, can download it by registering here. After registering, you’ll be provided a link to download it.

    I knew that only having 65 minutes would be a serious issue for the webinar because the discussion could take many worthwhile tangents. And it was. But alas, we stuck to the presentation agenda, stayed on schedule, and were able to address several audience questions.

    We had a lot of questions before and during the webinar. As customary, I’d like to address some of those as well as present the poll results here. First, the poll questions and results with accompanying pie charts to illustrate the results.

     

    Poll #1: For those of you who use post-processing, what are the reasons you use it?

    Total votes: 117

    Gakstatter comment: This is an interesting spread with no clear dominating reason. Based on data I’ve seen and data we collected, I’m not convinced that post-processing is more accurate. If it is, is it worth the extra 10%, 20%, or ??% accuracy? I understand the votes for more reliable corrections. There’s something to say for reverse processing (forwards and backwards).

     

    Poll #2: For those of you using post-processing, from where do you access GPS base station data?

    Total votes: 129

     

    Gakstatter comment: These answers don’t surprise me. National and regional CORS have become very prolific in the past 10 years.

     

    Poll #3: For those of you who use real-time DGPS/SBAS, what is the reason you use it?

     

    Total votes: 110

    Gakstatter comment: These answers surprised me a little. I thought more people would vote for “less complicated.” Does that percentage of users really need corrected coordinates in the field? Why? E-mail me a quick answer if you have a chance.

    Poll #4: For those of you using real-time DGPS/SBAS, from where do you access DGPS/SBAS corrections?

    Total votes: 129

    Gakstatter comment: This answer doesn’t surprise me at all. I suspect RTK networks will increase due to their continued proliferation and different levels of accuracy offered.

    Poll #5: When I purchase GPS/GNSS equipment in the future, I will likely select equipment that utilizes the following correction method (select all that apply):

    Total votes: 144

    Gakstatter comment: This was the only multi-answer poll. People could select more than one answer. These answers were surprisingly close. That surprised me. It didn’t surprise me that SBAS was the leader. It surprised me that post-processing is still as predominant as it is. If you have a chance, e-mail me a quick explanation as to why you will use post-processing in the future.

    Before diving into some audience questions, I’d like to clarify the slide illustrating the post-processing plot shown below.

    During the webinar, we were discussing PPP (precise-point positioning) when this slide was displayed. This data was not corrected via PPP, but rather post-processing the pseudorange data, which is the equivalent of L1 SBAS and L1 DGPS. The point was to show how SBAS/DGPS accuracy compares to post-processing. In the real world, you won’t post-process 24 hours of data. Some of you will post-process only a few minutes of data per session in cases where you need to turn off the receiver and travel between points. In other cases, users will keep the receiver tracking between points, allowing reverse processing to work more effectively.

    On to the Questions

     

    Question #1: Will there ever be a way in which the position of a rover can become fixed by using two fixed base stations?

    Gakstatter comment: SBAS does this already. SBAS’s consist of a number of base stations within the coverage area (e.g., WAAS has 38). Data from many base stations is used to compute the correction information sent to an SBAS-enabled GPS receiver.

    I’m assuming your reasoning is to improve position integrity.

    Another method of accomplishing this is by post-processing against more than one base station or switching between DGPS beacon stations. If they differ significantly, then you might want to compare against a third base station.
    Question #2: At what point in time will the strength of the GPS signal be increased? To what strength will this occur? 500 times more powerful? What improvements in signal reception will be experienced? Indoor my house reception?
    Gakstatter comment: The GPS broadcast strength is increased with new GPS satellite model. For example, the current Block IIF satellite broadcasts the new L5 signal about four times stronger than L2C. While no one can be sure yet as to how much this will improve indoor positioning, there will be some marginal improvement in conditions where GPS doesn’t operate very well today. Also helping will be the improved code and error-correcting techniques that should make operating in difficult conditions a bit better, especially where there are a mixture of satellites with strong and weak signals.
    Also, it raises the issue of a viable L5 single frequency receiver, which should outperform the L1 C/A single frequency receivers of today.
    Question #3: NAD83, WGS84, ITRF differences, how to make the best choice?
    &nbsp
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    Gakstatter Comment: I don’t think there is an incorrect choice, except maybe that NAD83 is a 2D system and will eventually give way to a 3D system, but that won’t happen in the U.S. for many years.
    Otherwise, it’s a question of matching disparate data sets. Probably the #1 question I hear from users is “why doesn’t my GPS data line up with my basemap?” The answer is almost always a difference in datums. Many papers have been written on this. Click here for a good PowerPoint presentation created by Dave Doyle of the National Geodetic Survey.
    Question #4: Are there any open source post-processing software programs available?
    Gakstatter Comment: Mike suggested looking here….http://gpspp.sakura.ne.jp/rtklib/rtklib.htm
    Question #5: If a person uses real-time correction satellites, is there a need to post-process?
    Gakstatter Comment: It’s rare that someone would do both, but not out of the question. For example, one might rely primarily on real-time corrections and record raw data for post-processing in case there is a problem receiving the real-time corrections. The opposite is true, too. One might rely primarily on post-processing and use real-time corrections as a back-up in case there is a problem with post-processing.
    Caveat emptor: There are probably datum differences between the sources of real-time and post-processing corrections. This needs to be reconciled when combining data that has used the two sources.
    Question #6: Is it possible to post-process data without using a DGPS?
    Gakstatter Comment: Yes, all that is required for post-processing is the ability to record raw observation data.
    Question #7: Are there geographic areas in the U.S. that are not covered by NGS CORS stations?
    Gakstatter Comment: No, not for pseudorange (L1) differential corrections. The distance to the base station will vary depending on where you are located and thus may affect your accuracy to some degree, but the density of CORS in the U.S. is such that you will never be more than a couple of hundred kilometers from a base station and likely much closer.
    A side note: Back in the mid-1990s, I remember experimenting with post-processing software we were developing. At that time, I tried post-processing data collected in Oregon with a base station located in Atlanta, Georgia. This was a 2,500 km baseline. It produced a result, albeit not one I would necessarily trust. The only limitation is that the two units must track common GPS satellites. With that length of baseline, it’s possible that only half of the satellites tracked may be in common.
    Question #8: What is the ideal distance range from a CORS station to your site to use post-processing?
    Gakstatter Comment: Ideally, as close as possible. The further you are from a base station, the more potential error will be introduced due to atmospheric differences between the two locations. As stated above, the density of CORS (at least in the U.S. and many parts of the world) are such that the nearest base station is quite near and likely no more than a couple of hundred kilometers away.
    Question #9: What is the trade-off between short observation time (couple of minutes) to position accuracy when using post-processing?
    Gakstatter Comment: Ok, remember we are talking about pseudorange corrections (as opposed to carrier phase). Given that the receiver has been tracking satellites for a period of time (let’s say two minutes), the observation times only need to be a few seconds for each feature to be mapped.
    For example, if you are mapping utility poles and don’t turn off the receiver between poles, you only need a few seconds (5-10 seconds) of data for each pole and average it for the final coordinate. Think about if you’re mapping a road centerline. You’ll likely record data while moving, so each second you are recording a new position.
    Question #10: What about the vertical correction? I see in the slide an antenna carried in a backpack. Is the antenna placed at ground level for point? Is there a constant correction required?
    Gakstatter Comment: Vertical accuracy is typically worse than horizontal accuracy by a factor of 1.5-2.0 due to the inferior satellite geometry, especially in areas of hilly terrain and/or trees/buildings where the horizon is blocked. Good geometry for vertical positioning requires tracking a number of GPS satellites that are low on the horizon.
    Question #11: What is the future of DGPS? I heard Coast Guard beacons were going away?
    Gakstatter Comment: The beacon stations operated by the U.S. Coast Guard are not in jeopardy and never have been. Neither have the marine beacons in the other 40+ countries that broadcast GPS corrections. However, the U.S. Department of Transportation operates 29 inland stations in the U.S. which have faced budget challenges the past few years. In April 2008, the U.S. DOT issued a policy decision to continue operating the 29 inland sites. Construction of seven sites remains that would allow the Nationwide DGPS to reach Initial Operating Capability (IOC), which would provide coverage to 99% of the continental U.S. No budget has been approved for the construction of those seven sites.

     

    Question #12: Can you briefly explain the difference between DGPS & RTK?
    Gakstatter comment: Here are a couple of good websites that explain each of these techniques. Essentially, DGPS is a real-time GPS positioning technique accurate to about 30 centimeters at the very best. RTK is a real-time GPS positioning technique accurate to about 1 centimeter.
    Question #13: How much time do you need to get the position from the base station for real-time DGPS?
    Gakstatter comment: Assuming both receivers are already tracking satellites, your receivers will begin using the base-station corrections as soon as the data link is made between the two.
    Question #14: Can you comment on advantages (if any) of using corrections from a network RTK service for DGPS corrections. Any advantages on eliminating base separation?
    Gakstatter comment: I’ve heard that DGPS corrections are optimized within an RTK Network. However, I need to research this a bit further to better understand the true advantages, if any.
    Whitehead Comment: A virtual base station (VBS) solution could be formed using the network. Thus differential GPS could exhibit the same advantages using such a network that RTK does (cancellation of atmosphere errors). The software would have to support this.
    Note though that if close to one of the Reference Stations in the network, it is probably best to just use the nearest Reference station as this will best cancel the atmosphere errors. When in the middle the network, the VBS solution would use surrounding reference stations to provide a good approximation of atmospheric errors and then output a correction that looked like it originated from a reference station (virtual station ) near to the users receiver.
    Question #15: What is up with PRN 135? Still on station?
    Gakstatter comment: Communication has be re-established with WAAS PRN 135 and is being tested by its owner, Intelsat, as well as the Federal Aviation Administration (FAA). See a detailed article by clicking here. The latest information I heard is that it’s currently at 93°W longitude undergoing testing. If the testing is successful, it will be re-located back to 133°W longitude and brought back into WAAS service. A timeline has not been published, but I’m guessing within the next 30-60 days.
    Question #16: We used to hear that your point accuracy degraded as the distance from the base station increased. One reason we used to post process. Is this still a factor?
    Gakstatter Comment: Due to advancements in GPS technology, it’s not as much of an issue as it used to be. I think this is illustrated in the results we achieved in our 24 hr test data.
    Ten years ago, it would be hard to find a GPS L1 receiver that would receive DGPS corrections from a beacon station 184km away and still achieve sub-meter horizontal accuracy at the 95% confidence level.
    I’m not saying the distance is negligible. There still the issue of tropospheric, ionospheric and satellite orbit errors as you move farther away from the base station. But, it’s certainly less of a factor than it was before.
    Whitehead Comment:
    Question #17: If we use WAAS correction, does it really help to try to use a post-processing type of software afterward? So far we just use WAAS correction.
    Gakstatter Comment: One of the reasons we collected data using several sources of real-time corrections and also showed the results of post-processing was to illustrate the differences between the two.
    If you follow proper procedures, there’s no reason to think that accuracy obtained using WAAS will differ significantly from accuracy obtained using post-processing. This is assuming that you’re using a single-frequency GPS receiver and post-processing using pseudorange corrections and not carrier-phase processing. Some receivers like the Trimble GeoXH are actually dual-frequency receivers and so data from it will likely surpass the accuracy of WAAS if you’re using its dual-frequency antenna and equivalent post-processing software.
    By proper WAAS procedures, I mean letting it track for five minutes upon initial start-up to allow it to download a current ionospheric map.
    Question #18: Does SBAS use 1 receiver and no base station? Expensive?
    Gakstatter Comment: SBAS uses 1 receiver and a lot of base stations. You just don’t have to pay for the SBAS base stations (or to use them.) The signal, like GPS, is provided free of charge.
    SBAS consists of a network of base stations (WAAS has 38) and communications satellites that broadcast corrections to users on the ground (or aviation users in the air).
    Question #19: How far north in Alberta is WAAS coverage available and useful?
    Gakstatter Comment: The primary concern would be visibility of the WAAS GEO satellite that broadcasts the correction data. Following is a map that illustrates the coverage. The contour lines are degrees above the horizon for which the two WAAS GEO satellites are visible.
    Solid line = PRN 138, Dashed line = PRN 133
    Question #20: Do you have any comments about CDGPS in Canada/US?
    Gakstatter comment: Sadly, the CDGPS service is being decommissioned March 31. You can read about it here. 
    Question #21: I am hearing from my state specialists (NRCS) regarding the LightSquared issue. We are advising working through the PNT ExComm and our cooperating partners.
    Gakstatter comment: This is a potentially serious issue for GPS users. Click here for the latest news as of February 1.
    Question #22: Where do you find the DGPS beacon station list and what is available to you?
    Gakstatter comment: I’m not sure if this is 100% complete, but it’s the most complete list I’ve seen. Click here.
    Question #23: Are most mapping-grade GPS receivers (for example Trimble GeoXh) equipped off the shelf to receive beacon signals?
    Gakstatter comment: Some receivers are equipped off-the-shelf, others are not (such as the GeoXH) and require additional hardware.
    Question #24: In which areas is it possible to use corrections from OmniSTAR?
    Gakstatter comment: Click here to view worldwide maps of OmniSTAR coverage.
    Question #25: Was the Garmin set to WAAS?
    Gakstatter comment: Yes, during the 24-hour data collection session, the Garmin unit was receiving WAAS 100% of the time as far as we could tell. The purpose of the 24-hour test period was to able to randomly sample data during that period to arrive at the accuracy statistics we presented. I randomly sampled the dataset several time
    s (averaging 10 seconds worth of positions 200 times) and the results were consistent with what we presented.
    Question #26: How does post processing account for ionosphere or troposphere errors if receiver is geographically far away from the base station? If not, does DGPS and WAAS provide better accuracy and integrity?
    Whitehead comment: Post Processing using a CORS station would take the nearest station and do differential GPS which cancels common errors in ionosphere and troposphere (ionosphere and troposphere are both temporally and spatially correlated) so if the CORS station is close, there will be good cancellation. If the receiver is far, the algorithms could use a troposphere model to account for the differential troposphere (as was done in the Presentation for BeaconT) and this would probably cancel troposphere so that remaining errors were sub-decimeter level. Differential Ionosphere errors could also be easily modeled with good results. It is likely that the performance could be made to easily surpass SBAS.
    DGPS would suffer from the same effects as does post processing, and maybe even more so since a model of differential atmosphere errors is rarely used. SBAS will likely provide better accuracy in situations where you are far from a base station.
    Question #27: What is Beacon T?
    Gakstatter Comment: While collecting data to present at the webinar, Mike noticed there was a bias in the beacon measurements. The beacon station is located ~184km away at about 7,000 ft elevation while the test site was at about 1,000 ft elevation. Initially, Mike wasn’t modeling the troposphere difference between the base and rover.
    To model the troposphere, Mike said he used a troposphere model to figure out troposphere in both locations, and then subtract the two. Although the models are not necessarily that accurate in an absolute sense, the differential tropo between the two locations is fairly accurate using the models. This differential tropo allows the receiver to correct the tropo in the base station differential to make it appear as if it originated in the rover location. Mike said he could’ve done the same for the ionosphere, but he didn’t since that is it usually less of a factor. After using the modified tropo model (Beacon T), the height bias was around 1/2 meter, which could be attributable the ionosphere. The horizontal bias is small, as you can see in the results.
    Using this troposphere model resulted in a significant improvement over the original solution.
    Question #28: Why is VBS better than WAAS?
    Gakstatter Comment: It surprised me too. The receiver used was the same that was used for beacon and WAAS. I contacted OmniSTAR for their opinion.
    John Pointon of OmniSTAR responds: “There have been incremental improvements in the VBS service over the years, mostly improvements in modeling and processing. We have added two or three extra reference stations but that hasn’t been the most critical improvement, just helped in some specific areas. These, combined with the relatively benign solar environment, result in VBS accuracy which, although not equivalent to our dual-frequency and multi-system solutions, is consistently better than either Beacon or WAAS.”
    Whitehead Comment: In the past, we’ve seen similar performance from both OmniStar VBS and WAAS.  Different atmosphere conditions and different locations can affect the performance of both. We’ve seen situations where WAAS is better.  It is probably fair to say that OmniStar is more focused on accuracy, whereas WAAS is focused on integrity.  It may be wise to do a comparison in the particular area where you operate.  Note, however, that in the US, OmniStar is referenced to NAD83 whereas WAAS is references to ITRF so positions reports between the two can differ by several meters.
    Question #29: When I look at your scatter plot, I have to ask if short-term point averaging is really effective at achieving more accurate positions?
    Gakstatter Comment: I think it’s well accepted that you are wasting time by occupying a point for 180 seconds. That said, there’s something to be said for letting the receiver track satellites for a period of time (1-2 minutes) before storing 5-10 seconds of data. Of course, if the receiver is already tracking satellites, then it’s not necessary to wait. The idea is to let the measurements settle down and take advantage of carrier-phase smoothing if the receiver uses that technique.

    Question #30: Could you go into PPP a bit more? How does it work?

    Gakstatter Comment: We opened a can of worms by discussing PPP. It’s an entirely different subject that I will cover in a future article. In the meantime, you can read Dr. Richard Langley’s article on PPP here.

    Question #31: How do you test the accuracy of SBAS collected data?

    Gakstatter Comment: In the U.S., it’s easy. Find a local survey mark using the National Geodetic Survey website. Printout the ITRF coordinates of the survey mark. If they aren’t on the datasheet, you can convert from NAD83/CORS96 to ITRF using the HTDP program. Compare the coordinates output by your GPS receiver to the coordinates of the survey mark.
    If you’re located outside of the U.S., look for a similar government agency in your country that maintains a record of survey marks. It’s vital that you are comparing coordinates referenced to the same datums.

     

    Question #32: Will there be any disadvantage if we use a EGNOS corrections in Kuwait, if we receive EGNOS?

    Whitehead Comment: Kuwait is outside the EGNOS coverage zone, so satellites to the south may not even have Clock and Orbit correctors available, which means the Receiver could not compute a correction for these satellites.  Unless the receiver can mix differentially cor
    rected ranges with non-differentially corrected ranges, it would likely drop the satellites in the south that had no corrections. This would then reduce PDOP and thus accuracy. Mixing differentially corrected ranges with non-differentially corrected ranges may give worse accuracy than no corrections at all since the SBAS system may have clock or other biases relative to GPS.
    By the way, I wish the SBAS providers would get together and share data so that they each could provide world-wide orbits and clocks. Then it would matter less if you were outside the coverage area.
    Gakstatter Comment: I’ve heard that EGNOS is planning an expansion to the south and east, so Kuwai may eventually be within the EGNOS coverage footprint. Also, you’ll want to monitor the progress of India’s GAGAN system, which is a similar SBAS. It’s possible you might fall within the GAGAN extrapolated footprint for non-aviation users.
    We covered most of the questions posed by the audience. If we didn’t address yours or didn’t provide a complete enough answer for you, please e-mail me and I’ll do my best to answer you.
    As I mentioned above, we had quite a few questions about PPP. It’s a technology that’s worthy of further coverage and discussion. Look for a future article on it.
    Thanks, and see you next time.
    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

     

  • 2011: The Year for Galileo

    Back in December 2006, I wrote about the momentum of Galileo (Europe’s planned satellite navigation system) in an article discussing GNSS trends. Galileo has been discussed off and on for well over a decade and was a hot topic for a number of years. In fact, back around 2001, the U.S. really didn’t want the European Union to embark on the project. While there was not a clear policy against Galileo, certainly the sentiment was questioning the creation of another satellite navigation system when GPS already exists that’s free for everyone to use. Ok, it probably wasn’t that simple, but you get my point. No bueno from the U.S. at that time.

    The following is an EU slide that illustrates why the EU wants to develop its own satellite navigation system similar to GPS:

    Source: European Commission – Montpellier, France – October 2010

     

    Then, in 2004, the U.S. government abruptly changed its tune. It really doesn’t matter why and I’m not sure I’d believe the answer if I was given one, but President George HW Bush instituted a new policy that encouraged international cooperation. The U.S. SPACE-BASED POSITIONING, NAVIGATION, AND TIMING POLICY issued in 2004 stated, among other things, that the United States shall:

    “Seek to ensure that foreign space-based positioning, navigation, and timing systems are interoperable with the civil services of the Global Positioning System and its augmentations in order to benefit civil, commercial, and scientific users worldwide. At a minimum, seek to ensure that foreign systems are compatible with the Global Positioning System and its augmentations and address mutual security concerns with foreign providers to prevent hostile use of space-based positioning, navigation, and timing services;”

    Also in 2004, the U.S. and European Union signed the landmark GPS-Galileo Agreement that established a basis of cooperation. This was great news for the GNSS user community. More satellites and more signals usually equates to better performance.

    The next policy update after 2004 was last year (2010) and it was simply titled “NATIONAL SPACE POLICY“. The sentiment regarding international cooperation was the same, if not leaning more towards cooperation:

    “Engage with foreign GNSS providers to encourage compatibility and interoperability, promote transparency in civil service provision, and enable market access for U.S. industry;”

    After the 2004 GPS-Galileo policy was published, the question from the civil user community was, “When are we going to have satellites in orbit broadcasting signals we can use?”

    The answer to that question wasn’t easy, and took longer to answer than anyone predicted, including myself.

    Now, we have the answer.

    Unlike GPS and GLONASS, Galileo is a civilian project, not a military-funded one. I’m not saying GPS and GLONASS were easy to fund, but the core application was defined (military use), and the funding required to develop and maintain GPS and GLONASS is drawn from the military budget. Furthermore, the European Union is comprised of 27 member countries. The political dynamics are, obviously, very complex.

    The Galileo funding modeling initially was to be a public-private partnership (PPP). Part of it would be funded with public money and part of it would be funded by a consortium of companies. But, that wasn’t so easy. How much funding would each contribute? What’s the return on investment? How would it generate revenue? Would there be a tax receiver sales? Would there be a user charge?

    We’re not talking about small sum of money. We’re talking about several billion Euros just to get it off the ground.Think about it, how much money has the U.S. military spent to develop GPS? $30-$35 billion for development, deployment and long-term maintenance. Granted, Galileo will cost a lot less than that, but it’s still a healthy sum that no company would be willing to gamble without a solid return-on-investment (ROI) argument.

    Eventually, the PPP (Private-Public Partnership) funding model was abandoned and in late 2007, and as described in a January 2008 GPS World article:

    “European officials responsible for the EU budget said they had found funds for Galileo, proposing to draw unused money originally earmarked for natural resources programs this year and next. The move would provide some €2.4 billion ($3.3 billion) for Galileo — the budgetary shortfall left with the dissolution of the public/private partnerships — over the course of the next six years. The following month, European parliamentarians agreed with the plan, but felt it didn’t go far enough. They boosted proposed funding for Galileo, increasing the money set aside for the program in 2008 to €739 million ($1.06 billion), up from the much more modest €151 million under the transport officials’ original proposal for next year.

    Not all were sold on public funding for Galileo. But in November, European officials said they had ironed out their differences. At the 11th hour came heated debate about how Galileo funding and contracts would be awarded among member states and their respective aerospace companies. Eventually, a final accord was reached. Europe anticipates spending €3.7 billion on Galileo through 2013.”

    (Updated figures: €2.1 billion for IOV and €3.4 billion for FOC)

    That was three years ago. The EU folks have been working hard since then, but talk is cheap and people stopped talking about Galileo with the exception of a few information spikes here and there. There was nothing else to say until now.

    2011 is the Year for Galileo

    Galileo will likely meet a major milestone this summer, launching their first two satellites for in-orbit validation. But unlike the two Galileo test satellites already in orbit (GIOVE-A and GIOVE-B), these satellites will be part of the planned 30-satellite operating constellation.

    For you Galileo naysayers, the EU is past the point of no return. Eighteen satellites are contracted. There is no reversing the process. And, if I were to place a bet, it’s very unlikely to stall at 18. That would be sort of like building a structure, but not finishing the interior.

    Although I haven’t seen a detailed launch schedule or control segment plan, the latest Galileo public document I’ve read (European Commission – Montpellier, October 2010) presents the following timeline:

    2011/2012 – In-Orbit validation: Four IOV satellites and ground segment (based on European Commission presentation from October 2010).

    2014/2015 – Initial Operating Capability for early services — 18 satellites (based on European Commission presentation from October 2010).

    2019/2020 – Full Operating Capability — 30 satellites
    (based on mid-term review released January 18, 2011)

    2014 Will Be the Year of Cheap GNSS Accuracy

    I believe the magic year for GNSS will be 2014. That’s when GNSS receivers are going to be very interesting.

    Why?

    It’s no secret that I think the new L5 signal is a game-changer. Last summer I wrote an article titled “What’s Going to Happen When High-Accuracy GPS is Cheap?”  It’s all about L5.

    L1/L5 dual-frequency receivers are going to be cheap, and accurate. Today, dual-frequency (L1/L2) receivers are thousands of dollars. L1/L5 receivers will be a fraction of that cost because open signal specifications will lead to increased competition.

    As I mentioned in the article last summer, the GPS Directorate is planned to have 24 satellites broadcasting L5 by 2019. The beauty of Galileo is that it can cut that time in half and make it happen by 2014, only three years from now. Here’s how.

    Since Galileo supports L1 and L5 similar to GPS, you only need 12 x GPS satellites broadcasting L5 and 12 x Galileo satellites broadcasting L5 to have something close to 24 satellites broadcasting L5.

    The BIG question is if the U.S. and EU will coordinate orbit slots so the 12 x GPS and 12 x Galileo satellites are in a somewhat optimal 24-slot constellation instead of an uncoordinated configuration. The civil economic benefit from taking advantage of L5 as soon as possible would be substantial. Just this week, the EU issued a report stating that 6-7% of the GDP of EU countries is dependent on satellite navigation. Better accuracy enabled by L1/L5 will spur a mind-boggling number of new applications that will further broaden the GNSS user base and economic impact. It would also stimulate GNSS receiver development from a much broader range of GNSS receiver designers than we see today.

    With a combined GPS/Galileo constellation, not only will accuracy become cheaper, but availability will increase significantly. The new GPS 24+ 3 configuration is certainly a big help for high precision users with respect to availability. Can you imagine how much precise positioning availability will improve when 18 Galileo satellites (not to mention 30) are added to the mix? Last summer, the EU-U.S. Cooperation on Satellite Navigation Working Group C published a report entitled “Combined Performance for Open GPS/Galileo Receivers.” The report succinctly draws the following conclusion, with which I wholeheartedly agree:

    “The studies demonstrate and quantify the improvements that can be expected when using GPS and Galileo open services in combination under different environmental conditions. In all studied cases, the combination of GPS and Galileo led to noteworthy performance improvements as compared to single system performance. The most significant improvement is for partially obscured environments, where buildings, trees or terrain block portions of the sky. The increased number of satellites available provides robust performance even as some signals are blocked, which is reflected in a significant increase of positioning accuracy and availability.”

    Following are some data from the report that back up the conclusions on availability.

    Availability with a 15° elevation mask

    GPS only – 99.10%

    Galileo only – 100%

    GPS/Galileo – 100%

    Availability with a 30° degree elevation mask

    GPS only – 57.28%

    Galileo only – 75.02%

    GPS/Galileo – 98.93%

    Granted, you should take these numbers with a grain of salt. These are based on positioning with four satellites in view. The reality is that for high precision users, we need data from at least six satellites for robust positioning. But, I think the scale of improvement when going to GPS/Galileo constellation is obvious and will scale similarly when considering six satellite positioning.

    For all the reasons above, I’m putting my stamp on 2011 as being The Year of Galileo. Look forward to further coverage on Galileo in the coming months.

    Upcoming Jan. 26 Webinar: SBAS, DGPS or Post-processing? Which Should You Use?

    Speakers:

    Eric Gakstatter, Editor, Geospatial Solutions and Survey Scene newsletter &

    Dr. Mike Whitehead, VP of Technology at Hemisphere GPS

    Event Date: 01/26/2011 10:00 AM Pacific Standard Time, 5 PM GMT

    Tens of thousands of users around the world utilize GPS/GNSS receivers for mapping, surveying and navigating. Since autonomous GPS/GNSS typically does not provide the needed accuracy, users must rely on a source of GPS/GNSS corrections. There are three sources of GPS/GNSS corrections available to users who desire reliable GPS/GNSS accuracy in the sub-meter to three meter range: SBAS, DGPS and post-processing. Dr. Michael Whitehead, Chief Scientist at Hemisphere GPS, will join me in presenting a background on the three technologies as well as the strengths and weaknesses of each. I’ve known Mike for a number of years. He was an early innovator in the development of SBAS technology at Satloc as well as SBAS and DGPS receiver technology at Hemisphere GPS. He is one of the leading GNSS engineers in the world. I’m particularly excited about this event and promise a lively discussion that’s full of useful information, data and concepts that anyone using or considering using GPS/GNSS for mapping, surveying or navigating will find useful.

    Thanks, and see you next time.

    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

     

  • To Post-Process or Not to Post-Process, that Is the Question

    If you’ve been around GPS mapping for any length of time, I’m sure you’ve heard of post-processing, and you may have even experienced it yourself. If you used GPS for mapping in the ’90s, you almost certainly post-processed your data. In fact, sometimes you had to pay for access to GPS base-station data for post-processing. That’s hard to imagine given the widespread, worldwide availability of GPS base-station data on the web today.

    SBAS (WAAS/EGNOS/MSAS) didn’t exist, and for real-time corrections and DGPS (beacon) coverage was spotty at best, but real-time commercial DGPS services like OmniSTAR, Landstar, and Satloc were around.

    One thing is for sure, no matter what, you have to have some source of corrections to collect GPS data for GIS mapping. It’s commonly referred to as differential GPS correction. Essentially, your GPS receiver needs to reference another GPS receiver (base station) that’s set up on a known position.

    Grafnav Post-processing software

     

    There are two primary methods in which to apply a correction to your GPS data: post-processing differential correction and real-time DGPS.

    Post-processing

    When you’re collecting GPS data that’s going to be post-processed, you need a GPS receiver (and software) that’s going to be able to record satellite observation data. Otherwise, data is collected as one normally would in the field, whether it’s utility poles, manhole covers, road centerlines or polygons of any sort.

    The accuracy of the GPS data while you’re in the field is autonomous GPS, so it could be several meters or even ten meters or more. You can’t use this type of method for navigating to a point with any sort of accuracy better than a few meters.

    After you’re finished collecting your GPS data for the day, you go back to the office and download your data to your computer. Post-processing requires special software. That software will allow you to search the Internet for the closest GPS base station(s) to use as a source of GPS corrections. In previous years, it was a laborious task to search for GPS base-station data that was recorded the same time as you were in the field (remember UTC vs. local time?). That’s not the case any longer as advanced post-processing software has made this a more automated process. The software will search for the closest base station and automatically select the appropriate files to download.

    It takes specialized software and training to utilize post-processing effectively.

    Real-time DGPS

    This is a method of receiving GPS corrections while you’re in the field. The GPS corrections are applied in real-time so your positioning is accurate. This is  useful when you want to navigate to a particular point very accurately. In the 1990s, there were a number of DGPS services, mostly commercial. One would pay a monthly or annual subscription fee to receive the DGPS corrections. During that time, the U.S. Coast Guard started developing a system by which it will install GPS base stations near the major U.S. waterways (coastlines and major rivers). It set up large towers that would broadcast the corrections via 300 kHz radio. Most importantly, it broadcast the corrections free of charge. One only needed a “beacon receiver” to receive the corrections. The system didn’t cover the entire U.S., but it opened the eyes as to what was possible in terms of a regionwide, or nationwide, DGPS network of base stations.

    The U.S. Coast Guard concept is still used today in more than 40 countries for DGPS marine navigation. The same GPS correction signal is also used by many people using GPS for mapping.

    Around the same time, the Federal Aviation Administration (FAA) began developing a system to improve GPS integrity and accuracy. They called it WAAS (Wide Area Augmentation System). It was the first SBAS in the world and, upon being declared operational in 2003, is in use by thousands of people for GPS mapping. SBAS is a regional system. WAAS only covers North America (U.S., Canada, and Mexico). It has spawned a number of similar and compatible systems such as EGNOS in Western Europe and MSAS in Asia with GAGAN under development in India.

    There are several advantages and disadvantages to both post-processing and real-time DGPS for GPS mapping. The primary advantage of post-processing is that you don’t have to worry about a wireless data connection in the field. The primary advantage of real-time DGPS is that you get much better accuracy in the field. There are many other factors you should consider when deciding which method to use.

    In fact, I think it’s an interesting enough topic that I’m conducting a webinar later this month that will address both of these methods. I’ve invited Dr. Michael Whitehead to join me. He’s the head technology guy at Hemisphere GPS and has worked extensively developing high performance GPS receivers. He was also the chief architect at Satloc back in the late ’90s.

     

    Webinar: SBAS, DGPS or Post-processing? Which Should You Use?

    Speakers:

    Eric Gakstatter, Editor, Geospatial Solutions and Survey Scene newsletter &

    Dr. Mike Whitehead, VP of Technology at Hemisphere GPS

    Event Date: 01/26/2011 10:00 AM Pacific Standard Time, 5 PM GMT

    Tens of thousands of users around the world utilize GPS/GNSS receivers for mapping, surveying and navigating. Since autonomous GPS/GNSS typically does not provide the needed accuracy, users must rely on a source of GPS/GNSS corrections. There are three sources of GPS/GNSS corrections available to users who desire reliable GPS/GNSS accuracy in the sub-meter to three meter range: SBAS, DGPS and post-processing. Dr. Michael Whitehead, Chief Scientist at Hemisphere GPS, will join me in presenting a background on the three technologies as well as the strengths and weaknesses of each. I’ve known Mike for a number of years. He was an early innovator in the development of SBAS technology at Satloc as well as SBAS and DGPS receiver technology at Hemisphere GPS. He is one of the leading GNSS engineers in the world. I’m particularly excited about this event and promise a lively discussion that’s full of useful information, data and concepts that anyone using or considering using GPS/GNSS for mapping, surveying or navigating will find useful.

     

    Thanks, and see you next time.

    Follow me on Twitter at http://twitter.com/GPSGIS_Eric

  • Top Five Events in GPS/GNSS for 2010: A Year-End Review

    With this being my last column in 2010, I’m going to look back at the five significant GPS/GNSS events in 2010 that affected the surveying, mapping, engineering, construction, and natural resource users. Each of these had, or could’ve had, a significant effect on your GPS activities.

    These are listed in order of importance with #1 being the most important.

     

    1. GPS 24+3 constellation. The most important GPS/GNSS event in 2010 occurred back in January, when the Air Force announced it was implementing a new GPS 24+3 configuration. You can read about it in in more detail here, but the idea behind it was to eliminate GPS “brownouts.” These are periods in which there are fewer GPS satellites in view, and when combined with obstructions such as rugged terrain or trees or buildings, make GPS difficult to use.

    It’s especially an issue with real-time, high precision users (RTK) because RTK technology is satellite-hungry. It needs six or more satellites to provide a robust position solution.

    If you recall, in the new 24+3 configuration, there were three satellites moving significantly from their original slots (SVNs 24, 26 and 30). SVN 26 is already at its destination. SVN 26 is scheduled to reach it destination in January 2011. SVN 30 should have arrived at its destination in the past few days.

    In addition, three other satellites (SVNs 46, 55, and 56) are being shifted slightly. SVN 55 should arrive at its destination this month. SVNs 46 and 56 are scheduled to begin transitioning in January 2011 and should be complete in May/June 2011.

    By now, you should be seeing some improvements in GPS satellite visibility as the 24+3 configuration is almost complete. From the scenarios I plotted in this article, you can see that although you’ll see fewer peaks (high number of GPS satellites in view), you’ll also see fewer valleys (low number of GPS satellites in view). This should increase productivity for RTK users and users in environments where satellites signals are obstructed (such as under tree canopy).

     

    2. Launch of the first GPS Block IIF satellite. Although it doesn’t really help users at this point other than being another satellite to enter service, the Block IIF satellite launched in May is the first to broadcast the third civil signal, L5. The L5 civil signals marks the beginning of a new era in high-precision GPS positioning. The Block IIF launch was the catalyst for the article I wrote I entitled “What’s Going to Happen When High-Accuracy GPS is Cheap?”

    It’s just a teaser though, the launch of the next Block IIF isn’t until next summer at the earliest. Then, the next one is ???. They are being launched at a snail’s pace. Remember though, it costs upwards of $200 million to launch a satellite and since there’s already 30+ operational GPS satellites in orbit, it’s hard for the U.S. Congress and the U.S. Air Force to justify speeding up the launch schedule. During the last Air Force briefing I attended, the target was to have 24 satellites broadcasting L5 by 2019.

    Block IIF GPS satellite (Courtesy: The Boeing Co.)

    3. Continued development of GLONASS. Despite the recent launch failure (three GLONASS satellites crashed into the Pacific Ocean), the Russian Federation was still able to launch six new GLONASS satellites into orbit in 2010, and with another launch scheduled for later this month of the new GLONASS-K1 satellite, that will test the new CDMA capability for better compatibility with GPS.

    As it stands, there are 20 operational GLONASS satellites in orbit, with four more offline for maintenance and two reserved as spares. That’s 26 total. Furthermore, after the Dec. 5 launch failure, Russian Federal Space Agency Director Anatoly Perminov vowed to return the GLONASS constellation to 24 operational satellites by March 2011, something that hasn’t been accomplished since the mid-1990s (albeit briefly).

    A consistent and healthy number of GLONASS satellites in orbit has given receiver manufacturers more confidence to develop GPS/GLONASS receivers. Just this year, we’ve seen new receivers from several manufacturers that have taken GPS/GLONASS a step further in integrating them into handheld receivers as well as OEM board products.

    For users, the benefits are clear, with the new 24+3 GPS configuration and a healthy number of GLONASS satellites in orbit, GPS/GLONASS users are seeing the most satellites in view ever in the history of GPS/GLONASS. Signals from more satellites typically results in more robust positioning and improved productivity due to decreased down-time.

    Rocket launch containing three GLONASS satellites

     

    4. Solar activity affect on GPS. Solar activity was eerily quiet in 2010. The big news is that there was no news. There were some minor solar events in 2010, but despite what you may have read, none of them were strong enough or the type that would affect GPS operations.

    So, if your GPS receiver didn’t work at times this year, it wasn’t due to solar activity.

    With the peak of the current Solar Cycle (SC 24) estimated to occur in May 2013, solar activity should be ramping up in 2011. In August, I conducted a webinar that discussed, among other things, the subject of solar activity on GPS. You can read a summary of it here and even download the webinar presentation.

    You can be sure I’m closely monitoring solar activity for any events that look like they will have an effect on your GPS operations. I’m still working on my notification system and will keep you updated on that. Otherwise, the GPS World website is a good source for news in this area.

    Finally, I’ll be attending the Space Weather workshop in April 2011. Most, if not all, of the really smart space weather people from around the world gather and confer on space weather. I’ll be writing about what I hear and learn from these folks. But, the sun is a mysterious creature. I like to get definitive answers to my questions, but even some of the brightest scientists I know will answer with “I really don’t know” when I ask them about a certain behavior of the sun. Mother Nature is humbling at times.

    Solar Cycle 24 Prediction (Courtesy: NOAA Space Weather Prediction Center)

     

    5. The GEO failures of GAGAN and WAAS. Both the Indian Space Research Organisation (ISRO) and the U.S. Federal Aviation Administration (FAA) were delivered a hard lesson in SBAS GEO satellite management. The SBAS GEO satellites are the ones that broadcast the integrity and correction information to users. They are the critical communications link that connects the SBAS ground infrastructure to the end users. Without them, SBAS doesn’t work.

    In April, the ISRO rocket launch of their GAGAN GEO satellite failed, sending the critical GAGAN GEO satellite splashing into the Bay of Bengal. GAGAN is still in testing phase, so no users were affected, but it set back the GAGAN program. However, it didn’t delay GAGAN as much as I thought it might. Another GAGAN GEO is set to launch later this month (as of December 29, the launch date has now been pushed out to Q1 2011) with a second due to launch in the first part of 2012. The ISRO completed its Preliminary System Acceptance of GAGAN just a few days ago. The aviation-certified system is expected to be operational by June 2013. As with other SBAS, test signals usable by non-aviation users will likely be available during the testing phase, as early as 2011.

    Also in April 2010, it was reported that the contractor operating one of the FAA WAAS GEO satellites lost communication with the satellite (PRN 135). It was reportedly an unprecedented event. Initially, it was thought that PRN 135 would drift out of usable orbit within a few weeks, leaving North America with only a single WAAS GEO until a new one was brought into service (PRN 133 was already under testing). Things weren’t quite as bad as they seemed as PRN 135 ended up staying in a usable orbit up until PRN 133 testing was concluded.

    However, the defunct PRN 135 was at 133° west longitude and PRN 133 is at 98° west longitude. With the remaining GEO (PRN 138) at 107° west longitude, users in northwest Alaska do not have WAAS service. Since none of the GEO satellites are actually owned by the FAA, they have little say in the location of the GEO satellite. The FAA says they are working on putting two more GEOs into service, but that takes time, and it’s not measured in months, but rather years.

    I think the hard lesson is not to skimp on SBAS GEO satellites. Perhaps this event will make it easier for the FAA to sell the concept to Congress (for funding).

    If you’re an SBAS user, don’t let this bring you down. SBAS is here to stay, and likely you were not affected by any of the above. These past few days, I’ve been looking at SBAS data (and DGPS data) collected over a 24-hour period. The accuracy and stability is pretty impressive.

     

    That leads me into my last subject which is a webinar I’m conducting on January 26, 2011.

    It’s entitled: SBAS, DGPS or Post-processing? Which Should You Use?

    If you are using or plan on using GPS for mapping or surveying, you should seriously consider attending this webinar.

    Learn the real story behind each of these technologies without a marketing or salesperson’s bias.

    Tens of thousands of users around the world utilize GPS/GNSS receivers for mapping, surveying and navigating. Since autonomous GPS/GNSS typically does not provide the needed accuracy, users must rely on a source of GPS/GNSS corrections. There are three sources of GPS/GNSS corrections available to users who desire reliable GPS/GNSS accuracy in the sub-meter to three meter range: SBAS, DGPS and post-processing. Dr. Michael Whitehead, VP of Technology at Hemisphere GPS, will join me in presenting a background on the three technologies as well as the strengths and weaknesses of each.

    I’ve known Mike for a number of years. He was an early innovator in the development of SBAS technology at Satloc as well as SBAS and DGPS receiver technology at Hemisphere GPS. He is one of the leading GNSS engineers in the world. I’m particularly excited about this event and promise a lively discussion that’s full of useful information, data, and concepts that anyone using or considering using GPS/GNSS for mapping, surveying, or navigating will find useful.

    Have a safe and happy holiday and a Happy New Year. See you next year.

    Click here to follow me on Twitter.

     

     

     

  • What Do Your Colleagues Think? Part 2

    In my last column, I presented the poll results from my November 16 webinar “A Buyer’s Guide to GPS/GIS Mapping Equipment.” I’ve conducted many webinars over the years, and the audiences have been comprised of hundreds (if not thousands) of participants who have the ability to ask questions and also participate on various polls I conduct during the webinars. This column continues the look back at previous polls conducted during the various webinars in 2010 to give you an understanding of what your colleagues are thinking.

     

    August 31, 2010 Webinar: “Solar Activity, SBAS, and 24+3 GPS Constellation Updates”

    Poll #1 (Aug. 31, 2010 webinar): How concerned are you about solar activity affecting your GNSS operations?


    Gakstatter comment: These numbers don’t surprise me. Personally, I probably fall in the “Somewhat” category, but my GPS/GNSS field work is pretty flexible so I can easily adjust without much inconvenience. However, if I had several crews using GPS/GNSS on a daily or near-daily basis or I had equipment relying on GPS/GNSS, I think I’d be in the “Very” category because the $$ impact would be much higher.

    Poll #2 (Aug. 31, 2010 webinar): If it was available, would you be interested in receiving alerts/warnings of solar activity that may affect GNSS operations?


    Gakstatter comment: I’m not surprised at these results either. When I initially considered this poll, I was thinking about asking which type of platform you would prefer to receive alerts/warnings with the choices being Droid app, iPhone app, Blackberry app, text message, e-mail, etc. If you have a preference on that, fire off a quick e-mail to me. Secondly, a few of you pointed out that NASA has an app for this, but keep in mind that the system I’m considering is focused specifically on high-performance/precision GPS/GNSS users, which would eliminate a lot of the baggage of the alert/warning systems available today.

    Poll #3 (Aug. 31, 2010 webinar): Do any of your GPS receivers use SBAS (WAAS/EGNOS/MSAS) as a primary source of corrections?


    Gakstatter comment: Not much to say here except that a substantial number of commercial GPS users are relying on SBAS. This has definitely been the trend over the past five years.

    Poll #4 (Aug. 31, 2010 webinar): Do you expect that the GPS 24+3 configuration will improve your GPS productivity?

    Total votes: 172

    Gakstatter comment: Like most of you, I have great expectations for the 24+3 configuration. While launching more satellites with L5 would be nice, that’s a long-term effort, whereas the 24+3 configuration is something we will benefit from in a few months and are seeing some marginal benefit now. In January 2011, once all the satellites have arrived at their destination slots, I’ll plot new visibility charts and see where we stand.

    June 24, 2010 Webinar: “GIS Mapping for Forestry, Agriculture, and Other Natural Resource Professionals”

    Poll #1 (June 24, 2010 webinar): What kind of mapping data do you primarily collect?


    Gakstatter Comment: These results don’t surprise me. The only note I’d like to make is that some people collect point data in the field and then connect the points in the office to generate line and polygon data.

    Poll #2 (June 24, 2010 webinar): Is having an aerial photo or satellite imagery in the background important?


    Gakstatter Comment: Again, these results don’t surprise me. My feeling is that if imagery was easier to locate and integrate, nearly 100% of users would prefer them. The challenge is finding accessible, affordable imagery that is easy to integrate.

    Poll #3 (June 24, 2010 webinar): How much are you willing to spend on a GPS receiver? I’m going to list the possible answers here because they don’t fit in the bar graph.

    1. $0 – No thanks.
    2. $200-500. I’m satisfied with 3-5 meter accuracy, limited use under forest canopy and limited data collection functionality.
    3. $500-1,500. I’m satisfied with 3-5 meter accuracy and limited use under forest canopy, but want more mapping data collection functionality.
    4. $1,500-$3,000.  I want a sub-meter accurate GPS receiver that will perform well under forest canopy and I’m willing do a little work to put together my own mapping system.
    5. $3,000-6,000. I want an out-of-the-box, sub-meter accurate GPS receiver that’s ready to go and works well under forest canopy.
    6. $6,000-10,000. I want a high-performance GPS receiver that will give me centimeter-level horizontal and vertical accuracy, but also work well under forest canopy (not centimeter-level).

    height=”261″ alt=”” src=”/files/gpsworld/nodes/2010/10757/0624Poll3.jpg” />


    Gakstatter Comment: I was surprised at the number of respondents who selected the “high-end” system.

    Poll #4 (June 24, 2010 webinar): Select the three most important features you need in mapping software. I’m going to list the possible answers here because they don’t fit in the bar graph.

    1. Ability to draw points, lines and polygons on your computer using a mouse.
    2. Ability to manage digital photos associated with features on the map.
    3. Ability to plot a professional-looking map.
    4. Ability to import aerial/satellite imagery.
    5. Ability to measure distances between points and calculate areas of features.
    6. Ability to import a wide variety of vector data (including GPS).


    Gakstatter Comment: This is about what I expected. Of course, the ability to draw using a mouse is highly related to the ability to import imagery.

    April 22, 2010 Webinar: “GPS, GLONASS, and SBAS Constellation Updates”

     

    Poll #1 (April 22, 2010 webinar): Have you or your work crews had to stop or alter your work pattern due to the lack of GPS satellites?


    Gakstatter comment: This is consistent with other polls I’ve conducted regarding GPS satellite availability. The great majority of you (73%) expressed that you have to adjust your work pattern due to lack of satellites. The new GPS 24+3 configuration will help mitigate this problem (and the new configuration is largely complete). Read more about the new GPS 24+3 configuration in a three-part series I wrote earlier this year.

     

    Poll #2 

    (April 22, 2010 webinar): How often do you upgrade your GPS equipment?

     


    Gakstatter comment: There’s no clear pattern here except to say that 46% of the users wait until at least 3 years before they consider upgrading their GPS equipment. That makes sense to me.

     

    Poll #3 

    (April 22, 2010 webinar): Does any of your GNSS equipment utilize GLONASS?

     


    Gakstatter comment: When considering the result of this poll, keep in mind that there are very few “mapping-grade” receivers that are designed to utilize GLONASS (but that is changing). For example, there are very few, if any, sub-meter receivers that utilize GLONASS, primarily due to the lack of correction sources. SBAS doesn’t support GLONASS, DGPS (radiobeacon) doesn’t support GLONASS, and most CORS do not support GLONASS. Only recently did OmniSTAR begin supporting GLONASS. I think this trend in mapping-grade receivers supporting GLONASS will continue, although I doubt that SBAS or DGPS (radiobeacon) will support GLONASS in the foreseeable future.

    However, manufacturers have developed methods to utilize GLONASS measurements to augment GPS positioning without the need of an SBAS or DGPS correction.

     

    Poll #4 (April 22, 2010 webinar): Does any of your GNSS equipment utilize SBAS (WAAS/EGNOS/MSAS) as a primary source of corrections?

     


    Gakstatter comment: This poll result doesn’t surprise me. Given that SBAS corrections are widely available, free of charge, reasonably accurate, and require no action by the user, it makes a lot of sense they are being used.

    February 18, 2010 Webinar: “GPS for GIS Data Collection — 101”

     

    Poll #1 (February 18, 2010 webinar): Do you currently use GPS for collecting GIS data?

     

     

    Gakstatter: No comment of significance. Sort of a dumb question now that I look at it again. Sorry :-)

     

    Poll #2 (February 18, 2010 webinar): What accuracy do you require in a GPS mapping system?

     

    Gakstatter: I’ve asked this same question in more than one webinar. The
    response from this particular audience, which was substantially GIS-oriented, was that sub-meter (33.1%) and cm-level (28.4%) were the most preferred levels of accuracy, with 1-3 meters accuracy at 22.3%.

     

    Poll #3 (February 18, 2010 webinar): Select the three most important items to you in a GPS mapping system. 

    Gakstatter: This was a multi-answer question with the top three answers clearly being; collecting attribute data (selected by 88.1%), accuracy (selected by 87.1%), and cost (selected by 71%).

    Thanks, and see you next time.

    Follow me on Twitter at http://twitter.com/GPSGIS_Eric