Tag: Survey Scene

  • Survey Perspectives – October 2007

    ION GNSS 2007 Report

    I hope some of you had a chance to read my ION GNSS conference blog, as well as those of my fellow editors who attended the conference. I think Editor-in-Chief Alan Cameron’s brainstorm about this was very good, and I expect we will repeat next year. If you missed it, you can still view it on the GPS World Web site. It’s worth a few minutes of reading to get the flavor of what the hot issues were.

    For this newsletter, I’m going to hit the highlights and comment on them, so fasten your seatbelt.

    CGSIC  Meeting

    Every year, the CGSIC (Civil GPS Service Interface Committee) holds two days of meetings before the ION GNSS conference; this year was no different. There were status briefings on the different programs, such as GPS and GPS modernization, GLONASS, Galileo, Compass, QZSS, WAAS/EGNOS, NDGPS and other activities. The CGSIC provides PDFs of the presentation on its site.

    Satellite launch schedule. The GPS Wing plans to launch the rest of the IIR-Ms in FY08. One was launched last week, on October 17. Its designation will be PRN 15/SVN 55 when it’s declared operational in early November.

    The next launch is scheduled for December. Then March 2008. Then June 2008. The launch schedule for the last one hasn’t been announced yet.

    However, the GPS Wing said that they plan to launch the first Block IIF satellite (with L5 in addition to L2C) before they launch the last IIR-M. This will be interesting, because rumor has it that the Block IIF is waaaay behind schedule and has almost no chance of being ready in 2008.

    Another interesting twist is that Lockheed was awarded a contract last Spring to enable a IIR-M satellite to broadcast an L5 test signal. Something about protecting the L5 frequency with the ITU (United Nations International Telecommunication Union) until the first IIF is ready.

    GLONASS. For you GLONASS users (or potential ones), the future is brightening somewhat. I’ve been touting GLONASS for some time, and the reliability of operational satellites has been disappointing. One could say that this is due to the legacy satellites, which are averaging well under four years of operational life, but that isn’t the whole story. While the newer GLONASS-M satellites supposedly have a seven-year life guarantee, the track record for the GLONASS-M really isn’t that great. For example, of the three GLONASS-M satellites that were launched in December 2006, only one is operational today.

    There are seventeen GLONASS satellites in orbit. Only eleven are operational. Seven are the newer GLONASS-M models and four are the legacy models.

    The bright spot is that six more GLONASS-M satellites are scheduled to launch by the end of this year—three this month and three more in December. The number of usable GLONASS satellites really needs to improve. GLONASS can’t seem to get above 13 operational satellites, and many times it’s been down to 9. Don’t count on the six new satellites to be operational in the near future. Sometimes, it takes more than six months after launch for them to be declared operational. I wish it wasn’t the case, but that’s a fact. Sometimes, I beat up on the GPS Wing for their slow pace, but after they launch one, it’s operational within thirty days—and it’s reliable.

    The GLONASS folks also announced that they are migrating the datum used by GLONASS, named PZ-90, to the ITRF (International Terrestrial Reference Frame). The revised GLONASS datum is named PZ-90.02. It was implemented on September 20, 2007.

    It doesn’t match ITRF05 exactly, but I understand their intent is to do so eventually. They publish the PZ-90.02 difference from ITRF05 as:

    Delta X: -36cm
    Delta Y: +8cm
    Delta Z: +18cm
    There is no rotation.

    Lastly, the long-awaited news about GLONASS possibly migrating to CDMA (to be compatible with GPS and Galileo specs) was discussed. The decision seems final (except the final government stamp) that GLONASS will eventually offer a CDMA signal interoperable with GPS L1 (called L1CR) and GPS L5 (called L5R). Not much else to mention on this now because it’s years—even a decade—away from now, but good news for users nonetheless.

    Galileo. There’s a lot to write about this, but also nothing to write. As users, we would benefit tremendously from Galileo. But it’s time to quit talking and start doing. That’s not to say they haven’t been doing; hundreds of millions of dollars are being spent developing Galileo, but the same discussions about the benefits are becoming stale.

    The biggest, and possibly best, news is that the European Union is not considering the PPP (Private-Public Partnership) funding model any longer. Looks like it will be a publicly financed system, at least into initial operation.

    To borrow a slogan from Nike: Just Do It.

    NDGPS. I blogged quite a bit about this during the conference.

    Not much post-ION conference information on NDGPS. I see that the invitation for public comment on NDGPS is now closed. Last I checked, there were only about 42 public comments. I read through most of them; about 25 percent were not relevant. There were some very good comments in support of NDGPS.

    NDGPS is probably going to survive in one form or another. I think it’s likely that some stations will stay and some will go away. If that’s the case and the USCG picks up the 12 they say they will, then the reduction in coverage will be minimal. The other possibility is that once the purse-string folks understand the cost of shutting down a site, that may be a big enough deterrent that the DOT finds the budget dollars somewhere to keep them going.

    Satellite-Based Augmentation Systems (SBAS)

    WAAS. Finally, long-term WAAS geo configuration is settled. The two legacy WAAS geos stopped broadcasting a couple of months ago. Right after the ION conference, the WAAS ground software was upgraded to incorporate the new reference stations in Canada and Mexico. WAAS users in Southern California, Southern Texas, Maine and Minnesota should see improved performance. The FAA GNSS program manager, Leo Eldridge, also stated that they are considering adding a third WAAS geo at 125W longitude, but that would be 3-4 years down the road.

    EGNOS. The European Space Agency says EGNOS is in Initial Operations Phase (IOP) and expects it to enter Long-term Operations Phase (Safety-of-life, Commercial Services) in a couple of years. EGNOS is usable now and there are three broadcasting GEO satellites. See my July 2007 column for details.

    The ESA reports that EGNOS coverage will expand northward, and eventually into Africa.

    MSAS. MSAS was declared operational on September 27, 2007. There are two GEO satellites identified as PRN 129 and PRN 137; if your receiver doesn’t recognize them, check with the manufacturer for a firmware update. Ground users should be able to benefit from MSAS in a broad area including Australia. Here is a coverage map:

    Map of two GEO satellites - PRN 129 and PRN 137

    Industry Developments

    Javad GNSS. Ever the GNSS maverick, Dr. Javad Ashjaee came to an agreement with Topcon, and now both companies are free to compete in all markets as of January 2008. Ashjaee has plenty of experience competing in survey/construction, so I would expect to see his company introducing products to that market next year.

    Septentrio. It’s not often that you encounter a new designer of high-performance GNSS receivers. This little-known Belgian company might prove to be a factor in the GNSS market. They’ve positioned themselves as an OEM supplier, much like Novatel, so you probably won’t see their name on a product that you use, but they may make the guts of a product you use. They just opened a U.S. office in Los Angeles, California, that is run by the guy (Chris Litton) whose father (James Litton) founded NavCom Technology, a competitor of sorts. Weird.

    NavCom Technology . NavCom is a wholly owned subsidiary of John Deere Company that has been focused on providing precision agriculture solutions for their owner. Now, that may be changing. They’ve hired two salespeople to develop external sales to achieve “NavCom’s revenue and growth goals for GPS products and services in direct sales, government customers, system integrators, and OEMs,” according to their press release.

    Some of NavCom’s key engineers developed the first Leica survey receivers while at Magnavox, so they have the technical capability. But creating a better mousetrap in the survey/construction market isn’t necessarily the name of the game. They’ve got to have a solid dealer network, and that isn’t easy.

    Leica/Novatel. No big surprise here: Leica (Hexagon) bought Novatel for $390M ($50/share). Novatel has been Leica’s sole source of GNSS technology for several years. If you bought Novatel stock five years ago for a couple of bucks a share, you did well. Also, the Topcon/Sokkia acquisition is still waiting for Japanese government approval, and with Novatel being Sokkia’s source of supply for GNSS technology, Sokkia is in a really weird position.

  • Survey Perspectives – September 2007

    NAVCEN and the CGSIC

    I thought this would be a timely subject, since I’m heading off for two days of CGSIC/NAVCEN presentations before the ION GNSS 2007 conference starts on September 25. I’ll also be staying for the conference, and reporting back to you on what I hear there.

    NAVCEN is an acronym for the U.S. Coast Guard Navigation Center. Its mission, according to its website, is to “provide cutting edge services for safe, secure, and efficient maritime transportation.”

    CGSIC (est. 1987) is an acronym for the Civil GPS Service Interface Committee. It is the forum for the civil GPS community to communicate with GPS authorities, and vice versa. According to the CGSIC website, the committee “was established and chartered to identify civil GPS user needs in support of the Department of Transportation’s program to exchange information concerning GPS with the civil user community as part of the GPS ‘outreach’ program.”

    The NAVCEN and CGSIC work hand in hand in facilitating communications for the civil GPS community; NAVCEN coordinates and manages the CGSIC. The NAVCEN site is one that you should have bookmarked in your web browser; there’s a lot of good information there. Here are some examples:

    1. Notice Advisory to NAVSTAR Users (NANU) report: you can sign up for a daily e-mail that reports on the day-to-day status of the GPS constellation, or you can view the GPS constellation online. This is very helpful way to keep track of satellite outages that may affect your GPS field operations. For example, if a particular set of satellites is important to keep the PDOP low in your area, this is a good tool to let you know if one of those satellites is having a problem.

    2. GPS Status Message (TIS-PF-NISWS) — This is daily GPS status report. If you subscribe to this mailing list, you will be sent an e-mail within 60 minutes of notification by the U.S. Air Force of a change to the constellation.

    3. View and download the daily GPS almanac. (Both YUMA and SEM almanac formats — which most GPS mission planning software packages can handle — are available.)

    4. View a list of DGPS and NDGPS sites broadcasting corrections. If you’re not sure you will be in range of a DGPS or NDGPS broadcasting station, this site provides details on each broadcasting station, including the precise location of the station, signal strength, expected coverage area and transmitting frequency.

    The CGSIC coordinates some very informative meetings with very good information. Its membership is made up of U.S. and international private, government and industry user groups. The committee membership is free and open to anyone who is interested.

    CGSIC meets at least once per year in conjunction with ION GNSS, which is usually held in September. However, there are subcommittee meetings throughout the year. There are four subcommittees:

    The International Information Subcommittee last met in May 2007 in Geneva, Switzerland. Members are free to attend, but if you can’t, then you can download all of the presentations for a quick update. Going back and viewing previous years’ agendas and presentations is very informative.

    The U.S. States and Localities Subcommittee last met in June 2007 in Bend, Oregon. I attended this meeting. There was good discussion on NDGPS, NGS initiatives and Network RTK. The Subcommittee also met in June 2007 in Minnesota. Notice the central theme of both meetings: NDGPS (but that’s another story).

    The Survey, Mapping and Geosciences Subcommittee is a relatively new one. Not sure when they’ve last met, but I’ll get up to speed on that one at the CGSIC meeting. As for the Timing Subcommittee, I don’t stay current with that because it’s outside of the survey/mapping market.

    Next week’s annual ION GNSS CGSIC meeting looks to be a good one: two days packed with all that a GPS connoisseur like me can handle. Day One is high-level information — policy stuff as well as program status reports on GPS, L1C, WAAS/LAAS and NDGPS.

    Day Two is tough for me, because there are concurrent sessions by the three Subcommittees I follow:

    • GLONASS, Galileo, EGNOS, QZSS/MSAS, GBAS/GRAS, Beidou/Compass from the International Subcommittee.
    • HA-NDGPS, NDGPS and USCG DGPS from the U.S. States Subcommittee.
    • CORS/OPUS, various NGS initiatives, RTK Networks and Space weather from the Surveying, Mapping and Geosciences Subcommittee.

    You can find a detailed look next week’s CGSIC agenda here.

    This year, GPS World is doing something a little different, and I think you’ll like it. My e-newsletter colleagues and I will be your eyes and ears during the CGSIC and ION GNSS meetings; “We’re Bringing ION to you!” is the theme. We’ll be writing daily reports on subjects we think may interest you, and the website will be updated twice daily during the week.

    If there’s something in particular you want me to check out while at the conference, fire off an e-mail to [email protected], and I’ll do my best to cover it.

  • Survey Perspectives – August 2007

    GNSS Update,  Version 2.0

    I, along with John Flick, co-authored a fairly in-depth piece on GNSS in the April 2006 issue of Geospatial Solutions. The basics of that article are still applicable, but here’s an update on GNSS events that have transpired since then — with a bit of speculation and guesstimation thrown in.

    The most talked about GPS modernization subject since then is L2C.

    There are now three IIR-M satellites in orbit that are L2C-capable. Most GPS receiver manufacturers have introduced “L2C-capable” receivers. Although the GPS Wing reports that no data is currently broadcast on L2C, the pilot carrier for L2C is available and useful by L2C-capable receivers. In fact, some experts say that the data on L2C is less important than the carrier. The reason is that with the complexity of semicodeless (legacy) L1/L2 receivers, a real signal loss of 3dB on L2 results in a net loss of 6dB. Using the L2C carrier, it’s a 1:1 ratio.

    You can read an older (2001), yet still valid article written for GPS World on L2C. Ignore the dates, because they aren?t valid any longer. Also, ignore references to consumer L2C receivers. The viability of those was effectively nixed when Galileo decided not to use that frequency.

    Code on L2C will add some marginal benefit, but that won’t be available for a while still. The GPS ground infrastructure is aged and wasn’t designed to handle L2C codes. Some of the infrastructure dates back to the 1970s. Next month, the GPS control segment will undergo a major upgrade as part of the Architecture Evolution Plan (AEP).

    Still, the limiting factor for L2C users is the lack of satellites.

    AEP Upgrade

    The upgrade is a major step. But the GPS Wing says they’ve been preparing for more than a year for the transition. Some observers have voiced a sort of “the sky is falling” doom that GPS may stop working when they attempt the upgrade. I don’t buy that. I’ll worry about many other things before I worry about that. As my wife told me last weekend while we were watching the Blue Angels (U.S. Navy fighter aircraft demonstration team), “I’m glad those guys are on our side.”

    One other note on the AEP upgrade. The current GPS control segment infrastructure is only able to accommodate 32 satellites. Next month’s scheduled launch would bring the current constellation to 32. Given that there will be four remaining IIR-M satellites to be launched after next month’s launch, but no way to accommodate them other than removing serviceable satellites from the constellation, the time for increasing capabilities is officially here. This AEP upgrade will expand that number to 60 and render this a non-issue for decades to come.

    You can read more about the AEP upgrade here

    Satellite Launches

    Right now, there are five remaining Block IIR-M satellites to be launched. The last one was launched in late 2006. The good news is that the GPS Wing has stated one of their top priorities is to launch the remaining five. The next one is scheduled to launch next month. According to an interview by GPS World Editor-in-Chief Alan Cameron with then GPS Wing Commander, Col. Wesley Ballenger, Jr. back in March 2007, the schedule looks like this:

    September 2007
    December 2007
    March 2008
    June 2008
    September 2008

    As in the past, the schedule could slide due to various reasons (resources and/or technical primarily), but all indicators seem to point that the September launch is a “go” — except that it has now reportedly moved slightly to the left, to October 17. Politically, this launch is an important one because, traditionally, it goes up prior to or during the Institute of Navigation (ION) GNSS conference where the GPS Wing makes the “successful launch” announcement — except that won’t quite happen this time around

    For precision GPS users, does it really matter what the launch motivation is — as long as they keep doing it? I don’t think so. The bottom line is that more is better.

    Interesting Twist

    The GPS Wing has said their desire is to launch the first Block IIF satellite (L2C, L5) before all the IIR-Ms are launched. The reason is to be able to take time to flush out any bugs, especially in a new satellite model, that may occur.

    I have no doubt they’ve thought it through and it’s a solid strategy. But it sure complicates the scheduling and really lowers the confidence level that the IIR-M launch schedule will stick. Here’s why:

    The AEP upgrade mentioned above is required in order to control the Block IIFs. But, my understanding from the GPS Wing media conference call last week is that another software “update” (beyond next month’s AEP upgrade) is required to the control segment before the first Block IIF can be launched. According to the GPS Wing, that “update” will occur Spring/Summer 2008 and therefore push back the estimated IIF launch date of March-May 2008 to Summer-Fall 2008. One would think this would impact the IIR-M launch schedule.

    Furthermore, the Block IIF program has had its share of technical issues. Boeing is scheduled to deliver the first Block IIF in mid-December 2007 but that’s many months too optimistic. Rumor has it that it could be well into 2008 before the Block IIF is delivered. Then with testing and integration, we could be well into 2009 before it takes flight. It’s not hard to doubt the IIR-M launch schedule as laid out above.

    Testing L5 on IIR-M

    In April 2007, Lockheed was awarded a $6 million contract to develop and demonstrate a payload that will temporarily transmit L5 (1176Mhz) from a Block IIR-M satellite. L5 was originally planned for Block IIF satellites and it’s not likely this will change. All indicators seem to agree that this will be a non-operational, temporary test on one IIR-M to test L5 before Block IIFs are launched.

    Not a lot of info on this, but I expect a new press release shortly.

    More is Better

    As high-precision GPS users, we’re on the leading edge of GPS technology. We push the technology hard and therefore we feel the bumps in the road before anyone else. The biggest bump now is the lack of satellite observables. I can’t count the number of people who have emailed me about the “down-time” during the day due to the lack of GPS observables — even in the wide-open plains of mid-western America, not to mention the beautiful, foliage-laden, topographically-broken northeastern US.

    The bandaid for high-precision GPS users, to this point, has been to rely on the Russian system (GLONASS). Whereas three years ago, there were many high-precision, GPS-only receivers on the market, now they are the minority. Almost every high-precision GPS manufacturer offers a GPS/GLONASS receiver. But adding GLONASS to the mix isn’t enough. I’ve used GPS/GLONASS receivers. Sometimes GLONASS helps, sometimes it doesn’t. There aren’t enough GLONASS satellites to help all the time. But I generally advise high-precision users to spring the extra $$ for the GLONASS option because there’s not another choice if you want to add observables.

    There’s not enough space here to update you on GLONASS, Galileo, and other GPS modernization initiatives so look for those in the coming months. Also, the ION GNSS conference is next month and I’ll be sure to give you an update on what I hear. There should be some good stuff coming from that conference.

  • Survey Perspectives – July 2007

    EGNOS Embraces Ground Users The European Geostationary Navigation Overlay Service (EGNOS) is Europe’s version of the U.S. Wide Area Augmentation System (WAAS) with essentially the same mission. It offers GPS users in Europe more accurate and reliably GPS positioning. Like WAAS, EGNOS focuses on improving the integrity and accuracy of autonomous GPS positioning primarily by modeling refraction caused by the ionosphere. Also, EGNOS was designed to be compatible with WAAS so your WAAS-enabled receiver will work with EGNOS just fine. The system is similar to WAAS in that it’s an augmentation to GPS. It primarily consists of a network of ground reference stations (RIMS) and three broadcasting satellites. This is done via the network of ground stations spread out over Europe as follows:

    EGNOS

    RIMS = Ranging and Integrity Monitoring Stations MCC = Master Control Stations NLES = Navigation Land Earth Station PAFC = Performance and Assessment Check-out Platform ASQF = Application Specific Qualification Facility In a quick sentence, the MCCs process the data collected by the RIMSs and the NLESs send the processed data to the three geostationary satellites that rebroadcast to the users. Got that? As I mentioned, there are currently three EGNOS broadcasting satellites: -PRN 120 (Inmarsat 3 F2) located at 15.5 West Longitude. -PRN 126 (Inmarsat 3 F5) located at 25.0 East Longitude. -PRN 124 (Artemis) located at 21.5 East Longitude. PRN 120 and PRN 126 are to be used by the general public. PRN 124 is available to the public but designed for use by companies to “perform various tests on the system” according to the European Space Agency (ESA). Generally speaking, the user needs line-of-sight visibility to either PRN 120 or PRN 126 in order to use EGNOS (there are a couple of exceptions I’ll mention later). There is a nice online tool at http://www.lyngsat.com you can use to determine approximately how far above the horizon PRN 120 and PRN 126 are in your area: PRN 120 – http://www.lyngsat.com/tracker/inmar3f2.html PRN 126 – http://www.lyngsat.com/tracker/inmar3f5.html One major exception to the line-of-sight rule is something that significantly differentiates EGNOS from WAAS. The line-of-sight rule has been the major inhibitor for WAAS ground users. Some companies have used innovative methods to overcome this limitation, but EGNOS has taken it to another level. EGNOS has embraced the ground users — something that WAAS has done poorly. To address the needs of the ground users (engineering and scientific community), EGNOS developed Signal-in-Space through Internet (SISNeT). SISNeT is a method of distributing EGNOS corrections over the Internet instead of requiring line-of-sight visibility to PRN 120 or PRN 126. What a great idea! WAAS really missed the boat on this one. All users need is a mobile phone with a data plan (like network RTK) to connect to their GPS receiver and they don’t have to worry about EGNOS satellite visibility. Granted, if you’re using a consumer-grade receiver, this doesn’t make much sense. But if you’re using high performance receivers (1-2 meters) for mapping and you’re in an area where you won’t have consistent visibility to PRN 120 or PRN 126, this makes a lot of sense. Like WAAS, EGNOS accuracy claims (1-2 meters) are a little ambiguous and generally on the conservative side. Like WAAS, you need to be working inside the EGNOS IGP (Ionospheric Grid Point) area to take full advantage of EGNOS accuracy. Note that some receivers are designed to exploit EGNOS outside of the IGP area with some accuracy degradation, but your average consumer GPS unit won’t do this. The following graphic defines that area:

    A year ago, the ESA declared that EGNOS was declared “fully-deployed” for “non-safety of life” applications such as mapping. This is the so-called Initial Operations phase of EGNOS. Safety-of-life applications using EGNOS such as aviation navigation aren’t approved yet, but the news seems to be good. On June 28, 2007, the African aviation safety agency (ASECNA) signed up to cooperate with ESA to improve aviation traffic safety over the African continent. The ESA has done a really good job of publishing detailed information on EGNOS. There is even a website referred to as EGNOS for Professionals that gets as technical as most people would like. EGNOS web site – http://www.esa.int/esaNA/egnos.html EGNOS For Professionals web site – http://www.egnos-pro.esa.int/ EGNOS SISNeT web site – http://www.egnos-pro.esa.int/sisnet/index.html Lastly, I’ll leave you with some data collected last month. It’s always good to get a real field perspective. Through my grapevine, I was able to obtain data collected in Italy (June 2007) using EGNOS corrections. Enjoy. Here is the graphic plot:

    EGNOS

    Here is the tabular data:

    EGNOS EGNOS

  • Survey Perspectives – June 2007

    WAAS Up?

    It’s been about a year since I’ve touched on WAAS (Wide Area Augmentation System) with any depth, and a lot of things are happening on that front so I’d thought I’d give an update. Also, look for a column on EGNOS (Europe’s version of WAAS) in the next month or two.

    WAAS is finally going to settle down, in terms of the WAAS broadcasting satellites; the final one is scheduled to become operational (for aviation users) in mid-July. Although it should never have been a headache for ground users like us (many of us have been using the satellite for mapping for more than a year), it was — mainly because several manufacturers of mapping receivers insisted on allowing their receivers to use only WAAS in aviation mode, which didn’t make any sense.

    Anyway, two significant events will happen next month. One is mentioned above, which means that users in the eastern/northeastern US and eastern Canada who are using mapping receivers that require WAAS to be operational for aviation users will now be able to use WAAS more reliably.

    The other event happening next month is that the two legacy WAAS broadcasting satellites, POR (PRN 122) and AOR-W (PRN 134), will stop broadcasting WAAS information. This has been the FAA’s plan all along. It will leave two WAAS broadcasting satellites (PRN 135 and PRN 138) that provide dual coverage throughout the US. Alas, WAAS satellite visibility will never be as good as it was for northeastern US and northeastern Canadian users when AOR-W was at 54W longitude.

    After the two legacy WAAS satellites stop broadcasting, the coverage footprint will look like this:

    Legacy WAAS Satelite

    This will put the nearly 18-month WAAS satellite reconfiguration confusion to bed.

    Another major milestone for WAAS later this summer is an upgrade that will add four new reference stations in Canada and five in Mexico. Also, new reference stations in Alaska will be added to the Iono grid.

    What this means is that WAAS coverage will expand to the north (Canada) and south (Mexico). Users will also see improved performance on the fringes of the current WAAS service area (southern Texas, southern California, New England states, etc.).

    Following is a map of the Iono Grid Points (IGPs) for the current WAAS service area:

    Iono Grid Point - GPS

    And here’s a map of the IGPs for the expanded WAAS service area:

    IGPS  GPS WAAS

    WAAS Accuracy

    Even though the expanded IGPs have yet to be implemented, WAAS accuracy is impressive. The National Satellite Test Bed (NSTB) produces a WAAS Performance Report on a quarterly basis. Each GPS receiver collects about 7,000,000 each quarter, and the NSTB compiles and publishes the test results.

    Following are the results of Q1 2007:

    For a system that was originally specified to provide 7-meter accuracy, the performance is impressive. At the 95% confidence level, horizontal accuracy for all test sites across the CONUS and some in Alaska are all under a meter. Also, remember that these figures will improve with the addition of the new reference stations later this summer.

  • Survey Perspectives – May 2007

    The Dealer Shuffle

    Whether you live in London, Lagos, Lisbon, or Los Angeles, when you are looking to buy a survey instrument, most likely you have a “preferred” instrument distributor in mind. Maybe it’s the local Topcon dealer. Perhaps your Leica dealer has served you well. Or you might prefer the Trimble dealer in your area. All of the manufacturers have distributors signed up around the world. Some operate on a regional basis, serving several countries, while others serve one specific country.

    I raise this point because of recent, significant changes in the U.S. distribution of survey instruments. These include:

    • Topcon’s intent to acquire Sokkia (still subject to Japanese Fair Trade Commission approval).
    • Leica’s purchase of Allen Precision Equipment, Inc. (APE, Atlanta, Georgia), the largest nationwide catalog distributor of survey instruments in the United States and the largest Topcon distributor in the country.
    • Topcon’s purchase of Hayes Instrument Co., a regional and online distributor of Topcon, Magellan, TDS (Trimble), Sokkia, Nikon, and Carlson instruments.

    A little history. Generally, instrument distributors are independent companies that have distribution agreements with particular manufacturers. Sometimes, a distributor like APE will have agreements with several manufacturers. APE had (prior to being purchased by Leica Geosystems) distribution agreements with Topcon, Sokkia, and Magellan for GPS equipment.

    Another type of manufacturer/distributor arrangement is one like what Leica Geosystems has traditionally maintained in the U.S. They have one distributor that operates exclusively in a region, and no other distributor is permitted to sell in that region. In essence, the distributor is somewhat “protected” by Leica. In return for this protection, the distributor is not allowed to have a distribution agreement with a competing manufacturer.

    Outside of the U.S., there may be several distributors in a country, or there may be only one distributor for an entire country, or, in some cases, a distributor’s responsibility may include more than one country.

    Lastly, in other countries or regions outside of the U.S. where a suitable distributor does not exist or the country is very large, a manufacturer may set up its own regional office.

    The distributor is a very important part of the sales channel for the instrument manufacturer because, for the most part, the local distributor is the one that makes the sale and supports the customer. If the distributor does a good job of supporting the customer and building trust, the customer may be very loyal to the distributor. On the other hand, especially with GPS/GNSS equipment, the customer makes a significant investment training to learn a specific system. So are customers more loyal to the distributor or to the manufacturer?

    At the end of the day, I think they are more loyal to the manufacturer. Even though the customer may well prefer to work with a specific distributor, the significant investment in equipment and training in the manufacturer’s hardware/software trumps the relationship with the distributor. Not many customers are willing to retool their equipment, training, and procedures to stay loyal to a particular distributor.

    Back to current events. It’s been nearly two months since Topcon announced its intent to acquire Sokkia. There was some significance to the announcement in terms of brand differentiation and reconciling the Topcon and Sokkia distribution channels, but the synergy was plausible (refer to my March column for further details) and it didn’t upset the instrument distributor applecart in a significant way.

    Then along came Leica, who announced last week that it had acquired APE — a discount, nationwide, mail-order survey equipment supplier. APE is (was) Topcon’s largest U.S. distributor. In response to the purchase, Topcon announced it had severed its relationship with APE. In one fell swoop, a decades-long relationship was ended.

    On its website, APE stated that it “wished to continue representing all current product lines, including Topcon.” But the site goes on to say, “However, Topcon has chosen not to support our mission…” It doesn’t take a brain surgeon to understand why Topcon cut off the relationship.

    With its largest U.S. distributor cast away, Topcon was left with a big hole to fill. Within days of the Leica announcement, Topcon announced it had purchased Hayes Instrument Co. of Shelbyville, Tennessee. Hayes is a regional and online distributor of survey instruments which has garnered a reasonable reputation of providing quality technical support. Hayes is also a distributor of Magellan, Sokkia, TDS, Nikon, and Carlson. Topcon also announced Hayes will be opening an Atlanta, Georgia, office by the end of June. Clearly Hayes gives Topcon the springboard to expand their distribution quickly in the southeastern U.S. — where APE is the most dominant. This is damage control at its best and actually is a better long-term solution for Topcon, in my opinion.

    What I don’t get is how Leica is going to reconcile the APE purchase with its U.S. distributors. Leica has traditionally protected its distributor network fairly well, so on the surface the APE purchase seems really out of character. Perhaps APE was purchased to “fill in the blanks” where good Leica distributor coverage is lacking. Rumor has it there was a Leica distributor meeting last Monday (May 14th). It will be interesting to hear the fallout from that meeting.

    One thing is for sure: the dust hasn’t settled yet.

  • Survey Perspectives – April 2007

    Getting Personal, Now

    Ok, this column is supposed to be about high-precision GNSS, right? Well, who would have ever thought I’d be inclined to write about consumer GPS receivers? Certainly not me. Sometimes, I even speak rather condescendingly about those “Wal-Mart GPS units” because they seem to be mis-used so often in the survey/construction business.

    But with the explosive growth of Personal Navigation Devices (PNDs) and being the GPS technology-aholic I am, I had to give some of these a try. Surprisingly, I became addicted to them in short order. Mind you, I already have an in-dash GPS navigation system in my car so this isn’t a new concept to me. So why the big fuss?

    First of all, let’s define a PND so everyone’s on the same page.

    The newer PNDs are roughly the size of a slice of French bread with a 3”-4” LCD touch screen. Its primary function is to guide you from Point A to Point B by providing you turn-by-turn instructions on the map screen and via voice instructions. Seriously — it talks to you. It typically comes with a street/address map database of the region where you bought it such as North America, Europe, etc. It runs on batteries or vehicle power and comes with some sort of windshield or dashboard mount.

    Whereas legacy PNDs were bulky and ran a short time on batteries and were really designed to stay mounted in your car, the newer PNDs are slim. They are designed to be truly portable with features that support “grab and go” functionality like ruggedness and extended battery operations.

    The PND did its job of getting me to where I needed to go. But the great part about it was that when I needed to alter plans, like a last-minute dinner meeting, it was perfect. With my old Mapquest method, I would have scrambled to find directions.

    But, secondly, perhaps what surprised me most and what prompted me to focus this month’s column on PNDs is the response I’ve been receiving from people who see me using the PND. I’m not talking about soccer Mom’s or Joe consumer. I’m talking about architects, construction superintendents, engineers: professional types. I’ve been on project sites where these types of people see me using the PND and they start asking questions.

    Most see it as a really productive business tool because they spend a lot of time traveling from one project site to another and aren’t necessarily familiar with the local hotels, restaurants, reprographic vendors, construction material vendors, and so on.

    Some have even exclaimed they can’t believe there’s not a monthly subscription fee. There’s not. Although after a couple of years of ownership, you’d probably want to purchase an updated map database.

    So the pessimist in me asked what happens if I become too dependent on the thing. After three days in San Francisco, I’d used the PND exclusively to navigate my way around the different suburbs. At the end of my trip, I dialed up the rental car location on the PND and let her take me home. Sure enough, about 10 min. from the airport, the screen went blank. No warning, no nothing. Dead battery. After a few seconds of “uh oh, what am I’m going to do now?” I remember I packed the car charger. I pulled over, plugged it in and off I went. But, it made me think about what I would have done otherwise. My conclusion was that, worst case, I pull over and ask for directions.

    The attractive feature of the “grab and go” functionality with new generation PNDs is that they aren’t tied to a specific vehicle. I found myself throwing it on the seat of rental cars and not using the windshield mount at all. To me, there was not enough value in hooking it up all that mounting hardware. I’d rather stuff it in my laptop bag and pull it out when I need it. I can imagine a small survey outfit having one unit in the office that folks check out for the day no matter which rig they are taking in the field.

    Another attractive feature for survey/construction professionals is that some of the new generation PNDs allow you to load topo maps in addition to having turn-by-turn directions, points of interest, etc.

    Time is money and it doesn’t take an MBA to figure out that if the PND saves time getting folks to each project site faster, it’s a no brainer at the ~$500 price tag.

    L1 RTK follow-up

    I promised I wouldn’t visit this subject again until products starting hitting the streets. It’s starting to happen. read more >>

  • DIRECTIONS 2007: Survey & Construction

    Momentum is a powerful phenomenon. When thought of in terms of a moving object, its mass and velocity can be measured. In other respects, it’s immeasurable. Feelings of confidence, trust, and faith can’t be hard-coded — but can make the difference between winning and losing. Whether in the context of a football game, the stock market, or a presidential election, positive momentum builds confidence, and confidence feeds the momentum. The Big Mo.

    In 2006, GPS constellation health has declined, but a well-timed presentation by Brad Parkinson at the ION GNSS 2006 conference has injected renewed enthusiasm into the GPS program. Parkinson’s call for a 30-plus satellite constellation may constitute a boon for GPS survey/mapping users in 2007. More satellite signals and healthier satellites mean increased productivity. While 2006 saw two IIR-M satellite launches, look for double that in 2007. Even if new launches don’t improve the PDOP spikes, we’ll have more reliable hardware in orbit. The Big Mo is rolling.

    The short-term benefit of the IIR-M launches is a healthier constellation. Another, longer-term benefit comes from the addition of the second civil frequency. L2C may bring some value to L1/L2 users in 2007, but with only eight IIR-Ms even potentially operational by year’s end (assuming five are launched in 2007), plus the requirement to have an L2C-capable reference station, the bennies will be limited.

    GLONASS is still a crapshoot and may likely continue that way into 2007, but it doesn’t matter because its value is augmenting GPS. Up until a few months ago, it had The Big Mo on its side. Then GLONASS headed south in a hurry in September, when nearly a half dozen satellites were declared unusable “due to maintenance.” This continued for 30-plus days. The good news is that the Russians are launching GLONASS satellites at a pretty good clip, and GPS/GLONASS users don’t need a full GLONASS constellation for it to be useful. Three more are scheduled to launch this month and six are scheduled for launch in 2007.

    Even if only half of those become operational, GPS/GLONASS users will feel the love in 2007. Worldwide GLONASS usage will increase significantly in 2007 now that all major survey instrument manufacturers have introduced and will begin rolling out their GPS/GLONASS-capable products. The Big Mo will return.

    Galileo won’t do anything for the survey/mapping user in 2007, but that doesn’t mean you don’t keep tabs on it. Galileo has the potential to deliver Huge Mo for survey/mapping — just not in 2007. The business model will continue to receive scrutiny, and the discussion of military use will spin things around a bit, but development and testing will continue. The key news to look for in 2007 will be any significant delays. 2008 should be a Big Mo year for Galileo if the program can stay on target, and if tight GPS interoperability is realized.

    Satellite-based augmentation systems (SBASs) like the United States’ WAAS, Europe’s EGNOS, Japan’s MSAS, and India’s GAGAN also have Big Mo on their side. Virtually every GPS receiver shipped today is SBAS-capable. WAAS will finally stabilize with respect to the communication satellite adjustments made in 2006, and EGNOS should be declared operational. The worldwide SBAS user base will continue to show strong double-digit if not triple-digit growth.

    NDGPS (National Differential GPS), another GPS augmentation system, will encounter the most significant crossroad in its decade-long history of service in 2007. Lack of support threatens the program’s existence. The worst-case scenario is that NDGPS will shut down as early as October 2007, leaving the U.S. Coast Guard to operate only 40 or so maritime DGPS broadcast stations along coastlines and major waterways. Big Mo left some time ago, and No Mo has moved in.

    Reshaping the Marketplace. The most interesting GPS survey/mapping innovation for 2007?

    L1 RTK.

    While not the most innovative technology because it’s been possible for many years, it holds great interest because of its potential to reshape the survey/mapping marketplace. It will fill a gap between L1 static systems and high-end L1/L2 RTK systems. Those L1 static users who could not overcome the financial jump to an L1/L2 RTK system costing several tens of thousands of dollars will now have the productivity of RTK within reach.

    Why now, and not five years ago? Follow the money to find the answer. L1/L2 RTK systems still run in the US$25-45,000 range. Competition among high-end GPS manufacturers is heating up, so they’re looking for opportunity. L1 RTK systems will be half that price — maybe even one third. Yes, baseline lengths will be limited to a few kilometers, and initialization times will be measured in terms of minutes rather than seconds, but the accuracy will be the just as good as high-end L1/L2 RTK systems.

    Satellite constellation health will be the wildcard for L1 RTK. 2006 was not a good year for the GPS constellation. With L1 RTK and a weak constellation, productivity would be an issue, especially if you aren’t operating in a really clear open-sky environment. However, the good news is that it seems GPS Wing of the U.S. Air Force is in giddy-up mode again. If they share Parkinson’s vision of a 30-plus satellite constellation, L1 RTK could end up being a very productive tool — with Big Mo on its side.

    Eric Gakstatter is editor of GPS World’s Survey & Construction e-newsletter. Free subscription available.

    More DIRECTIONS 2007

    Every December GPS World invites experts to share insights on what the new year holds. Here are additional views in the Directions 2007 feature:

    SYSTEM DESIGN & TEST
    Opportunity, Innovation — and Choice
    By Charles F. Trimble and F. Michael Swiek

    MILITARY & GOVERNMENT
    Through a Glass, Darkly
    By John T. Kelly

    AVIONICS & TRANSPORTATION
    Modernizing, Expanding GNSS Use
    By Bill Thompson

    LOCATION-BASED SERVICES
    As Navigation Goes, So Goes LBS
    By Mike Sheldrick

  • NDGPS Heads Toward the Budget Chop Block

    Nationwide Differential GPS (NDGPS) heads toward the budget chop block. Its 2007 allocation has been scaled back to zero.  As in aught, nought, zot.

    NDGPS, also referred to as the Coast Guard differential system, made its first NDGPS broadcast in the early-to-mid-90s. After years of industry talk about real-time DGPS, NDGPS was the first, mostly reliable source of real-time corrections that was free of charge (via your tax dollars).

    Support from the mapping and non-aviation navigation markets pushed the government (the Department of Transportation took the lead) to continue the build-out of the NDGPS network. Each year, more sites were added, and NDGPS became a solid resource for folks wanting a free source of DGPS corrections that delivered meter-level accuracy. They just had to buy the hardware (beacon receiver and antenna) to use it. Today, more than ten years later, there are more than 80 broadcasting sites — and more planned — spread out over the continental United States, Alaska, and Hawaii, providing free DGPS coverage used by hundreds if not thousands of users on a daily basis.

    A successful program?

    Up to and including FY 2006, Congress and the President allocated a substantial annual budget for NDGPS improvements, operations, and maintenance. For example, the FY 2006 budget came to approximately $10 million — half of what was originally requested. Almost $100 million more is needed to complete the network build-out. After that, about $9.2 million is needed annually to operate and maintain the system.

    However, unlike years past, this years budget (FY2007) for NDGPS improvements, operations and maintenance is………………….$0 (zero). The rumor mill says that since there’s no money to operate and maintain, some sites may actually be shut down. That’s not the case according to the Department of Transportation, however.

    “The FY06 budget provides approximately $10 million for the NDGPS program.  These funds will be used to operate and maintain the existing NDGPS system through October 1, 2007”, says Steven Kulm, Director, Office of Pubic Affairs for the DOT’s Federal Railroad Administration.

    So that means no money for new sites that were planned for FY 20007, and no money for developing new technologies such as High Accuracy (HA)-NDGPS.

    Wow, what went wrong?

    The problem facing NDGPS today, in my opinion, is the lack of a “killer app.” In other words it’s a neat tool and serves hundreds (if not thousands) of people on a daily basis, but if it disappeared tomorrow, life would go on. Therefore, when it comes to cutting the budget during tight times, programs like NDGPS are prime targets.

    Now, I’m guessing the DOT may say that PTC (Positive Train Control) may be the killer app for NDGPS because it reportedly will save the railroad industry “billions” each year. That may be so, but if it was that easy to sell, then no one would be hacking away at the relatively puny NDGPS budget.

    Putting the pressure on NDGPS is the Federal Aviation Administration’s (FAA) Wide Area Augmentation Service (WAAS) program. Like NDGPS, WAAS is a free government service providing corrections to improve accuracy and reliability of GPS positioning. The FAA began developing WAAS in the mid-90s and it was declared operational in July 2003.

    WAAS has two things going for it that NDGPS doesn’t.

    • A killer app. The future of aviation navigation is based squarely on GPS, and WAAS is an integral part of that program. The FAA is banking so heavily on GPS and has so many initiatives based on GPS, that there is no way it can back its way out of the program…and it shouldn’t. There are so many valuable uses for GPS in aviation that it boggles the mind. Some applications are focused on efficiency (e.g. better traffic control and throughput) and others are safety-of-life driven (e.g. situational awareness such as ADS-B). Because of this, the FY 2007 budget for WAAS is close to $100 million.

    • WAAS is easy to use for non-aviation folks like us. It’s a no-brainer and it comes standard on every GPS receiver you purchase today. Whereas NDGPS requires the use of additional hardware (a 300khz receiver) and a separate antenna, no additional hardware or software is required to use WAAS. Using WAAS is virtually automatic. NDGPS receivers will never reach that level of simplicity. Good quality NDGPS antennas, by their nature, are bulky and I have serious doubts that any company will attempt to design an NDGPS receiver-on-a-chip (some have tried and failed), especially at this late stage of the game. With those two strikes, consumer GPS units will never incorporate NDGPS technology. And thus NDGPS will never achieve mass-market status like WAAS already has.

    Availability

    The foothold that NDGPS-supporters are hanging onto is the issue of the correction availability. Whereas WAAS is satellite-based and is dependent on line-of-sight between the user and the broadcast satellite, NDGPS broadcasts corrections on the 283-325khz band and does not require line-of-site between the user and the transmitter. It can even be received inside some buildings. However, signal propagation is interrupted by rough terrain and in metro areas, and ambient radio interference can interrupt the signal too. Although it’s not a true national service, there are certainly areas where the NDGPS can be received and WAAS can’t. The reverse can be stated also.

    Accuracy

    The NDGPS vs. WAAS debate in the surveying/mapping community has been a lively one this past year. This is due largely to major GPS manufacturers introducing professional mapping GPS receivers that use WAAS to achieve meter-level accuracy. Although NDGPS has the capability of being more accurate than WAAS, meter-level accuracy seems to be good enough for most mapping applications given the additional expense and equipment overhead required to use NDGPS. Think about it: Garmin discontinued their NDGPS receiver product line and now every GPS product they sell is WAAS-enabled.

    Fate

    Clearly, from a funding perspective WAAS has won the battle for now and has NDGPS back on its heels. The next twelve months (or less) will determine the direction of the NDGPS program.

    “At this time, the U.S. Department of Transportation is deliberating how to administer the program in the future.  We anticipate the Administration’s proposed FY08 budget (to be released in early 2007) will provide guidance on what the future of NDGPS will be,” says Kulm.

    The challenge for NDGPS-supporters in the next few months is to not let the purse-string holders forget about NDGPS and its niche applications. If it’s business-as-usual in FY 2007 and the purse-string holders don’t feel the pain, what are the odds they’ll throw money at NDGPS in FY 2008?

    — Eric Gakstatter

  • No Joy in Surveyville

    I have something to say about our mainstay — GPS — and its troubles of late. So many people in the survey/mapping community have asked me when this problem is going to be resolved. The problem is there aren’t enough healthy satellites for surveying community to use.

    I think the GPS decision makers don’t believe there is a problem because
    with a clear sky, you still get a 3D position, anytime, anywhere in the world.
    Herein lies the problem: we don’t usually work in clear-sky environments.
    Neither do consumer GPS users. My Honda Odyssey GPS navigation system doesn’t
    get a GPS position fix nearly as much as it used to.

    (Just to clarify: I’ve spent the past 16 years in the GPS survey/mapping
    industry using many brands of GPS equipment and software. My first ten years
    in GPS were spent as a product manager and the last six years as a GPS user
    and consultant. I’m a non-partisan advocate for the GPS user community.)

    The fact is that GPS has suffered more outages to key satellites (or satellites
    in key orbital slots) in the past year than it has since GPS was declared operational
    in the early 90’s.

    PRN 25 has behaved like a legacy Jaguar automobile for the past 6+ months:
    an hour shut down for maintenance for every hour it has spent operational.
    Of course I’m exaggerating, kind of, but I’m sure you understand
    my point if you’ve been using RTK with any frequency for the past 6+
    months. I reported last month that the next GPS satellite launch (scheduled
    for September ’06) would most likely replace PRN 25 according to the
    Chief GPS Liaison at the USCG, Doug Louden. But I’m beginning to doubt
    this, given the precarious slot that PRN 30 occupies and its surprisingly rapid
    decline in health. PRN 30 is on its last clock from what I understand. It isn’t
    as old (9.5 yrs) as PRN 25 (14 yrs), but it’s still two years past its
    design life.

    Other GPS satellites are significantly past their design life and heading
    for failure. You can’t use RTK a full day with the current GPS constellation
    even with every satellite healthy. Take one out that’s in a key slot
    like PRN 25 or PRN 30 and it gets really ugly.

    I think it’s not unreasonable to ask the GPS JPO for a healthy, reliable
    constellation of GPS satellites.

    Delays in launching replacement satellites have been so significant that GPS
    users have quit asking me about new launches. It looks like only one will be
    launched in 2006 and only one will be launched in 2007 — if the schedule
    doesn’t slip further. This is a far cry from the “three-a-year” launch
    plan laid out a few years ago.

    I don’t believe the GPS JPO thinks there is a problem, but you only
    have to look at the new product introductions to understand that there is.  For
    years, most survey-grade GPS manufacturers ignored GLONASS and thought it would
    go away, and GPS would fill the bill. However, in the last 12 months, the number
    of survey-grade GPS manufacturers offering GPS/GLONASS products has at least
    doubled.

    Meanwhile, GLONASS is pushing forward with an aggressive launch schedule.
    Three in December ‘06, three in Q3 ’07 and three in Q4 ’07.
    Furthermore, the two new GLONASS satellites that are already in orbit are reportedly
    to be declared operational in the next 60 days. Granted, only time will tell
    if they can honor that schedule, but even launching half of what they plan
    would be significant.

    So, I’d like to raise my hand from the back of the classroom and say
    the Survey, Construction and GIS industry segments aren’t happy with
    the way GPS is performing these days.

    — Eric Gakstatter

  • Potential Problems for Users of Modernized GPS Signals inMixed-Mode Operations

    When the new flex power feature aboard PRN 17, the first IIR-M GPS satellite,
    was enabled for testing (for a very short period of time), a problem was observed
    by certain GPS users.

    PRN 17, the first IIR-M satellite launched in September 2005, began broadcasting
    the second GPS civil signal, L2C, in December 2005. PRN 17 is the first in
    the new generation of GPS satellites with a new feature called flex power.
    According to the U.S. Air Force, flex power adds the capability for the Department
    of Defense to increase power on both P- and M-code (both military) signals
    to defeat low-level enemy jamming.

    When flex power was enabled for testing (for a very short period of time),
    a problem was observed by certain GPS users. This problem was associated with
    the definition of the phase relationship between L2C and legacy L2 P/Y. In
    this scenario, users who are operating L1/L2/L2C GPS equipment, in conjunction
    with legacy L1/L2 GPS equipment, could have a problem maintaining carrier-phase
    ambiguity resolution with any modernized satellite operating in modes where
    signal phase relationships are changing or are unknown.

    This is not just a flex power issue, but a potential issue with any new modernized
    GPS signal if provisions are not included to inform users in real time of signal
    phase relationships. This is potentially a long-term problem because there
    will be a mixed set of modernized/legacy signals for an extended period of
    time, as well as a mixed set of modernized/legacy user equipment. The important
    thing is that these potential problems can be fixed by broadcasting appropriate
    data in the GPS navigation messages in a timely manner.

    This fix to this potential problem would slightly change the GPS user interface
    specifications and add bits for defining the phase relationship between the
    modernized and legacy signals. This data would have to be added to both the
    L1 and L2C signals since, for the time being, there is no data on the L2C signals.
    For L1C, (in the draft L1C specification) the phase relationship between L1C
    and L1 C/A has been defined. For L2 and L2C interoperability during modernization,
    a similar parameter to provide the phase relationship between the L2 P/Y and
    L2C is needed for mixed equipment processing. (Refer to Section 3.5.4.6 subframe
    3, page 7 signal phase of the newly released Draft IS-GPS-800 L1C specification
    dated April 19, 2006.)

    Another possible solution is for L2C-capable receivers in a network to track
    both L2C and L2 P/Y simultaneously, to directly measure the phase difference
    between the two phases. However, the drawback is that the more robust L2C signal
    will be tracked at times when the legacy L2 P/Y cannot — the main reason
    for implementing L2C in the first place.

  • L2C — not just vanilla GPS anymore

    Welcome to the second edition of GPS World’s Survey & Construction e-newsletter. My name is Eric Gakstatter ([email protected]). I’ve spent the past 16 years in the GPS survey/mapping industry using many brands of GPS equipment and software. My first ten years in GPS were spent as a product manager and the last six years as a GPS user and consultant. I’m a non-partisan advocate for the GPS user community.

    This subject of this month’s column is L2C. It’s not just about vanilla GPS anymore. GPS modernization weighs heavily in future of satellite surveying. What does L2C bring to the table? When do the new features become useful enough to start making equipment purchasing decisions? While some of the answers may be obvious, others may surprise you.

    First of all, I’ll preface this column by noting that L2C is only a small part of the Global Navigation Satellite System picture that includes L5, GPSIII,  Glonass (Russia’s satellite system) and Galileo (Europe’s satellite system). Discussing all of the GNSS components is too much for one column so I’ll be chipping away at all of them in the coming months.

    Last September (’05) was a big step for GPS modernization when the first IIR-M satellite was launched…starting the next phase of GPS with a second civilian signal (L2C). Currently, there is one civilian signal (L1 C/A). L2 was designed for military use…although civilian manufacturers have been very resourceful in developing codeless techniques for utilizing L2; therefore making dual frequency receivers (L1/L2) very useful for the user community.

    Basically, L2C can be viewed as an add-on feature to the existing L2 band. In practical terms, L2C will help in two areas:

    • It will allow for user receivers to more accurately correct for the error that is generated when the GPS signal passes through the Earth’s ionosphere. L2C provides manufacturers with a new code, enabling them to address the ionospheric delay in a more direct manner than the codeless techniques used by today’s dual frequency receivers. It will also open the door for non survey-grade GPS manufacturers to design survey-grade dual frequency receivers at a much lower R&D cost with fewer patent blocks.
    • Contrary to popular belief, the L2C signal is weaker (not stronger) than L1 C/A code. The idea that L2C will “punch through the trees” with a stronger signal is incorrect. What L2C does offer is a more robust code structure with improved error-correcting methods that will allow it to be used more effectively in marginal satellite signal conditions than what we experience today. Just how much it will help will only be known when the satellite constellation is in place and the receivers are developed to optimize it.

    These two enhancements will result in more competition in the survey-grade GPS receiver marketplace because survey-grade dual frequency receivers will be easier to design. With increased competition, it’s reasonable to expect more competitive prices. With L2C, you can also expect GPS to perform better in weaker satellite conditions.

    With the benefits of L2C to the survey/mapping market clearly established, when are we going to be able to use it? Well, it’s going to be awhile. The publicized year of 2010 is not realistic as this point. Educated speculation says that 2012 is more likely. Don’t forget that it’s not just a matter of tossing satellites into orbit. There are control and management systems on the ground that need to be developed, tested and rolled-out to make use of the new signal. After the hype generated last September when the first IIR-M satellite was launched, the delays in the follow-up IIR-M launches have been disappointing. For example, the launch scheduled for 1Q 2006 has been pushed out until September…a full year after the first IIR-M.

    From the launch schedule, you can see it’s a bit early to start making equipment purchasing decisions based on L2C. Yes, I think that manufacturers will do their best to exploit a partial constellation of L2C satellites and perhaps there will be some innovative
    developments in that area, but just note that by the time there is a minimum constellation of L2C satellites in orbit, there will be another two or three generations of receivers that will have been introduced to the market.

    I’m at the American Congress on Surveying and Mapping annual conference this week in Orlando. Look for my report on conference news in next month’s issue.