This month’s column deals with two troublesome topics: the U.S. government’s over-reliance on GPS, and the potential costs of GPS disruption toward which such a policy may be leading us.
First things first.
When someone utters the words “I’m nearly perfect,” get on your toes. Such self-appraisal usually masks something. It could be insecurity, denial, ignorance or simply fear. At the very least, some level of illusion, if not delusion, is involved.
The press release actually says, “The U.S. Air Force released two technical reports demonstrating that the Global Positioning System (GPS) continues to deliver exceptional performance to civilian users around the world….The 2014 and 2015 performance reports confirm that the GPS Standard Positioning Service (SPS) satisfied nearly all measurable performance commitments documented in the GPS SPS Performance Standard.”
Fair enough. Those are demonstrable facts. Nowhere does the release — other than in its headline — employ the words “perfect” or “near-perfect.”
The problem is, as current events repeatedly show, people remember only the headline. That may be all that they read or register in the first place.
Affixing the label “near-perfect” to GPS is “potentially dangerous,” points out Dana Goward of the Resilient PNT Foundation, “because it could exacerbate the public’s growing over-reliance on, and often blind faith in, GPS. Even if GPS did always perform perfectly, all kinds of things can happen to signals after they leave the satellites and before they get to receivers. Personal privacy devices, other jammers, spoofers, solar activity, other electromagnetic interference, even the local geography can significantly degrade or disable a receiver’s performance. That’s why in the GPS System Performance Standard the Air Force specifically says its responsibility ends once signals are in space.”
Perfection might exist in space, but it doesn’t down here.
Even in space, accidents sure will happen. The Air Force release documents GPS performance for 2014 and 2015. This conveniently draws up short of January 2016, when several GPS satellites broadcast a timing error that triggered equipment faults and failures globally for nearly 12 hours. Thus demonstrating something far from perfection.
Issuing a statement in the manner done on June 16 perpetuates a dangerous myth, keeps users in the dark about the actual state of affairs, cultivates a What-Me-Worry? approach to positioning, navigation and timing, and abets the lack of political will and understanding of GNSS vulnerabilities.
We have expanded the focus of this magazine to cover other technologies relevant and applicable to the field precisely because GPS, and by extension GNSS, great though they may be, are not perfect. Not even nearly.
At What Cost Ignorance?
A report recently compiled and released in the UK attempts to quantify the cost of a GNSS disruption, should one occur. The figure the authors came up with? 1 billion pounds sterling per day. That’s approximately $1,273,710,000.
Per day.
The report, available in either 11-page or 133-page versions, and titled The economic impact to the UK of a disruption to GNSS, looks at what would happen to the UK economy if GNSS were unavailable for five days. Five days is, indeed, a long time. One hopes that a fix could be obtained in less than that amount of time. But one never knows, does one?
“The economic impact to the UK of a five-day disruption to GNSS has been estimated at £5.2bn.” Thus the per diem figure above.
The report was commissioned by Innovate UK, the UK Space Agency and the Royal Institute of Navigation. It followed from the January 2016 accident referenced earlier, in which an error in the GPS signal from certain satellites, triggered by the decommissioning of one of those satellites, brought a number of key industrial servers to their knees. The episode lasted 12 hours.
This report hypothesizes a more fleshed-out disaster and estimates the likely impact of a disruption to GNSS availability for up to five days across ten application domains in the UK: Road, Rail, Aviation, Maritime, Food, Emergency and Justice Services, Surveying, Location-Based Services (LBS), Other Infrastructure, and Other Applications.
The report is worth reading, not only for its figures, methodology, and discussion of mitigation, but also for two salient pages: “A day in the UK with GNSS” and “A day in the UK without GNSS.” At home, on the move, with others, at work, at the shops, when things go wrong, back at home. A post-modern (or post-Beatles) “Day in the Life.”
Even if the hypothetical disruption were not to last 5 days, but a much shorter period, perusing the two chronologies of with and without can serve to remind us how many of our daily activities are keyed to and thus dependent on GPS/GNSS.
Having no viable, working back-up — not even on the visible horizon — to such an essential system makes sense how?
It’s been a few months since I’ve published a GSS Monthly newsletter column. What a busy few months it has been. It’s been all about UAVs, high-precision GNSS projects and GIS, with some conferences and workshops sprinkled in between. High-accuracy GNSS technology and UAV technology are hot trends— red hot.
UAVs: Prosumer and mapping on a slope
Obviously, consumer UAVs have exploded in the mainstream consumer electronics market during the past five years. Since the FAA began requiring UAVs to be registered in late 2015, far more UAVs have been registered (~700,000 to date) with the FAA than manned aircraft (~320,000).
In fact, the number of registered UAVs aircraft eclipsed registered manned aircraft more than a year ago! The FAA reported that at any one point during the day, there are ~7,000 manned aircraft flying in the U.S. airspace. That begs the question, how many UAVs are flying above our heads at any one point in time? No one can answer that question.
On the coattails of consumer UAVs in mainstream America is the use of UAVs in the USA’s commercial world. Since the FAA opened the floodgates in August 2016 to allow almost anyone to fly UAVs for business ($150 and answer 42 out of 60 questions correctly), lots and lots of companies are buying inexpensive “prosumer” UAVs and extracting tremendous value from them.
Prosumer electronics is equipment and software targeted at the consumer market but also good enough to be used for business. The UAV market is a perfect example of this. DJI, by far the biggest UAV manufacturer in the world at $1B+ in annual revenue, targets the mainstream consumer market and sells a huge number of low-, medium- and high-end UAVs to businesses. Think about it: You can buy a DJI Phantom 4 Pro at your local Apple Store and the next day be generating one-foot elevation contours on a project site!
Following is an example of a papermill I flew a few weeks ago. I flew it in less than one hour (50 acres), generated an orthophoto with 2.4-cm/pixel resolution and a digital elevation model (DEM) with 4.79-cm/pixel resolution.
Figure 1. 2.4-cm/pixel resolution orthophoto, 50 acres.Figure 2. DEM with 4.79-cm/pixel resolution of the same flight.Figure 3. Zoomed-in image of the same DEM.
The detailed data above, generated from a $1,500 UAV, is clearly outstanding. By the way, the purpose of the project was to determine the volume of the various stockpiles, which I’ve not computed yet. But if the volume calcs are close enough to the traditional terrestrial-based measuring methods, the UAV return on investment (ROI) argument will be hard to beat.
It takes ~14 hours each month to measure all the stockpiles on this site using traditional terrestrial measurement tools. Also, the measurements must be taken on the weekend when the site activity is minimal. It took less than one hour to fly the entire site, and I flew it twice (one time west-east direction at 80/80 overlap and one time north-south at 70/70 overlap) to make sure I had enough data. I mean, seriously, I drove 1.5 hours to the site. Why not spend another 20 minutes to fly it in a perpendicular direction?
To date, I’ve only flown relatively flat sites such as construction sites, agricultural fields, and industrial sites. That was until a couple of weeks ago. While I’ve become pretty comfortable at flying open and relatively flat sites over the past 18 months, I’ve not ventured into flying a site with a lot of elevation changes and tree canopy. I finally did that earlier this month, and it was both challenging and rewarding. There are a few problems on sites with major elevation changes and tall tree canopy:
A. Maintaining visual line of sight (VLOS) as required by the FAA.
B. Flying in such a manner that the image-processing software has good quality data to work with so you can generate the products you need.
The mission planning/control software plays a very important roll in this process. Well, it always does, but it really does in this case. Typically, the mission planning/control folks want you to fly at a consistent height above the ground so your overlap is consistent. This is very difficult to accomplish if you’re flying a site with a lot of elevation change. In that case, they typically tell you to launch from the highest (or nearly the highest) elevation point and fly at that elevation.
The problem this causes is that you could end up flying 500, 600 or 700 feet above ground level (AGL). For example, if you are flying a site with 500 feet of elevation change and you instruct the mission planning/control software to fly at 350 feet AGL, at some point in the project the UAV will be at 850 feet AGL. That can be a problem from both a regulatory standpoint (FAA allows UAV flights up to 400 feet AGL) and an image-processing standpoint.
Fortunately, the mission planning/control software I use just introduced a Terrain Awareness feature. It uses SRTM (Shuttle Radar Topography Mission) elevation data. Granted, it’s 30-meter pixel elevation data, so each elevation block is 30 meters x 30 meters, so I really wondered if the resolution was high enough. The site I was going to fly was only 60 acres in size and had 550 feet of elevation change. Note that the trees on the site had already been harvested, so the land was relatively clear. There’s about a 550-foot difference from the projected launch point (purple dot) to the northern and western end of the site. Following is the mission plan for the site I was planning to fly.
Figure 4. 60-acre site with ~550 feet of elevation change.
To give you an idea of the slope, the solid red lines in the following image are 100-foot elevation contour lines. The green triangle is the projected UAV launch point. This was a great launch point because I could see the entire site and maintain VLOS.
Figure 5. Site topo with projected UAV launch point.
I chose to fly the mission at 300 feet AGL. I figured it would be high enough if there was some “slop” in the SRTM elevation model. Still, I was concerned about the resolution of the SRTM data because at 300 feet AGL, my UAV would be flying below the launch elevation due to the extreme elevation slope on the site. Remember, the Terrain Awareness feature of the mission planning/control software is based on the SRTM elevation data, and not based on any sensors in the UAV itself — if the SRTM elevation data was incorrect, my UAV might crash into the ground.
Following is the SRTM elevation data along with the flight path data displayed in the mission planning/control software.
Figure 6. The projected UAV flight path based on the SRTM elevation data.
The moment of truth came when I launched the UAV from the start point (purple dot) and watched it rise to 300 feet AGL to start its mission. The first few swaths were uneventful. After that, it started to fly into the canyon, following the terrain as programmed, then rise up from the canyon during each pass. It was a thing of beauty to watch.
Unfortunately, about 70% of the way through the mission, it started raining, so we called it quits. However, we proved that at least on the four sites I flew that day, the SRTM data and Terrain Awareness feature were effective in collecting data in steep-slope environments. Following is the 2.69-cm/pixel orthophoto generated from the flight. Note the tracks where the logging rigs pulled the logs up the steep slope.
Figure 7. 2.69-cm/pixel resolution orthophoto.
Following is a zoomed-in view of the UAV launch site.
Figure 8. Zoomed-in view of the orthophoto.
Following is an image of the 5.37-cm/pixel DEM generated from the flight data. Notice the logging tracks.
Figure 9. 5.7-cm/pixel image of the DEM generated from the flight data.
Following is a zoomed in view of the 5.37-cm/pixel DEM image.
Figure 10. Zoomed-in 5.37-cm DEM image of UAV launch point.
The mission was successful in proving that SRTM elevation data was sufficient enough to fly a mission with a dynamic AGL. It handled the steep slopes by maintaining a sufficient AGL elevation as I hoped it would despite only having 30-meter x 30-meter block elevation resolution. The image processing software seemed to like the UAV data, as you can see from the results above. I didn’t have to spend any additional processing time over and above what I usually spend in order to generate these products.
I did experience a hiccup with the mission planning/control software running on my iPad Mini 2. It turns out that the Terrain Awareness feature in my mission planning/control software requires some extra CPU horsepower — the software overpowered my iPad Mini and crashed once during a mission. The UAV kept flying its intended course as instructed, but it stopped taking photos when the software crashed, so I brought it back to the launch point.
After visiting the software vendor’s website, it became clear to me that it’s probably time to upgrade my iPad Mini to the latest model to keep up with the new features being implemented in the software.
A Quick Note on High-Accuracy GNSS
In March, I attended the Hawaii GIS conference and decided to perform some benchmark testing on a survey mark using WAAS and a high-accuracy GNSS receiver.
My goal was two-fold.
See how WAAS is behaving in Hawaii. WAAS in Hawaii is an anomaly because it’s far away from the Continental U.S. (CONUS) where all the WAAS reference stations are located (there’s one in Honolulu, but that’s it). In other words, Hawaii is the most challenging place for WAAS accuracy in North America.
See how many GNSS satellites I could track and use in Hawaii.
Holy moly, was I surprised at how good it was. I’ve tested WAAS in Hawaii several times in the past many years. The last time I tested it was in 2013 and the GNSS receiver I used (GPS + GLONASS) achieved a steady 80-cm accuracy. That was pretty darned good for WAAS in Hawaii at that time.
I packed up some receivers and hiked about 4 miles to a survey mark I could find in Honolulu. I was a great survey mark for testing because it was on the sidewalk of a quiet residential street. Following is a photo of the survey mark.
Figure 11. PID DK4162 survey mark in Honolulu.
I set up on the survey mark and then looked at the satellites the receiver was tracking. I wanted to know how many GPS, GLONASS, Galileo and BeiDou satellites were being used. Following is a screen shot.
Figure 12. Total number of GNSS satellites being used – 23.
Twenty-three GNSS satellites being used! Are you kidding me? This is more than double the number of GPS satellites being used. This illustrates the power of four-constellation GNSS that is only going to continue to get better over the next several years.
What surprised me the most was the number of Galileo satellites being used, and this was before two Galileo satellites were declared healthy in late May.
My next test was to evaluate WAAS accuracy. Who cares how many satellites the receiver is using if the accuracy isn’t improved? I plumbed the receiver antenna on the survey mark and plotted ~7 minutes of data.
Figure 13. Accuracy plot compared to the DK4162 survey mark coordinates.
Yep, that’s about 30-cm accuracy over a 7-minute period. That’s better by a factor of two compared to the accuracy I saw in 2013. Sure, WAAS has improved somewhat, and maybe the ionosphere was particularly happy that day, but I have to believe that the additional GNSS satellites contributed the most to the improvement in accuracy. In the next few months, I’m going to be performing more tests with WAAS and RTK on my GNSS test course near my office. I’ll keep you posted on the results of those tests.
The Esri International User Conference – July 10-14
As usual, I’ll be attending the largest gathering of GIS professionals in the U.S. next month, the Esri International User Conference. 16,000 of our colleagues will descend upon San Diego to share, network and enjoy the spatialness that we have for one another.
If you’re interested, I’m giving a couple of presentations at the Esri UC:
Tuesday (July 11), 08:30 a.m., Room 28B (subject to change)
Paper Title: An Efficient, Accuracy Mobile GIS Workflow using RTK GNSS
Session Title: Mobile Data Collection
This is cool project I worked on with WaterOne, a large water utility, to design a real-time, high-accuracy GNSS workflow in the Esri environment. They are collecting data at the centimeter level for mapping their above-ground assets as well as new construction using tablet computers and RTK GNSS receivers.
Thursday (July 13), 8:30 a.m., Room 29C (subject to change)
Paper Title: UAV (drone) applications for water utilities
Session Title: Applied GIS: Three Unique Examples
This is some groundbreaking work I’ve done with American Water on using UAV technology for mapping and inspection. We did a lot of experimenting during the proof-of-concept phase to figure out what applications are practical and which aren’t.
The U.S. Air Force released two technical reports demonstrating that the Global Positioning System (GPS) continues to deliver exceptional performance to civilian users around the world, reported the Los Angeles Air Force Base.
Operated by the 50th Space Wing at Schriever Air Force Base, Colorado, the GPS constellation provides precise PNT services worldwide 24-hours a day, seven days a week.
The 2014 and 2015 performance reports confirm that the GPS Standard Positioning Service (SPS) satisfied nearly all measurable performance commitments documented in the GPS SPS Performance Standard, furthering the status of GPS as the “Gold Standard” for PNT.
The GPS Directorate at the U.S. Air Force’s Space and Missile Systems Center commissioned the GPS SPS performance reports to enhance public transparency of the real-world performance of civil GPS.
The GPS Directorate at the U.S. Air Force’s Space and Missile Systems Center commissioned the GPS SPS performance reports to enhance public transparency of the real-world performance of civil GPS. The reports confirm that GPS met all of the evaluated commitments for calendar years 2014 and 2015 with one exception.
This exception was that the reporting notification commitment for scheduled GPS satellite interruptions during calendar year 2014 was only met in 29 of 30 cases (96.7 percent). The vast majority of GPS users were not impacted by this single delayed notification. In this single case, the U.S. Air Force only provided 17 hours of advanced notice, as opposed to the SPS PS commitment of at least 48 hours advanced notice, before the scheduled satellite interruption.
The commitments evaluated in the reports include those of accuracy, integrity, continuity, and availability of the GPS signals-in-space. For example, the signal-in-space ranging accuracy of the GPS civil signals was significantly better than the published standard of “7.8 meters or better at the 95th percentile.” This metric represents a key component in the total “user range error” that GPS receivers experience.
Most impressively, the oldest GPS satellites still provided an average signal-in-space accuracy of 2.8 meters during their worst performing month of 2015 – surpassing the target accuracy metric by over 300 percent. On average, the signal-in-space accuracy of the GPS constellation in 2015 was 1.4 meters, which is a 0.4 meter improvement over the accuracy in 2013.
The GPS SPS performance reports are generated by Applied Research Laboratories, the University of Texas at Austin (ARL:UT), which is a Department of Defense University-Affiliated Research Center. Using data from 33 GPS monitoring and reference stations located around the globe, the ARL:UT team assesses GPS performance against the commitments defined in the 2008 GPS SPS Performance Standard. The ARL:UT reports focus on those commitments that can be verified by anyone with knowledge of standard GPS data analysis practices, familiarity with the relevant signal specifications, and access to a Global Navigation Satellite System data archive.
“The GPS Directorate remains committed to providing highly accurate and reliable PNT services to our users around the globe. The use of published standards to transparently guide data-driven decision making is how we have become the ‘Gold Standard’ in PNT,” said Col. Steven Whitney, director of the GPS Directorate. “The GPS Directorate is working every day on improved capabilities to ensure users receive the maximum benefit of the PNT services offered by GPS.”
ARL-UT expects to complete the 2016 SPS performance report later this year. The 2013, 2014 and 2015 reports are publicly available for free download. The National Coordination Office for Space-Based PNT maintains the GPS.gov website to provide official information about GPS to the public.
Air Force Space Command’s Space and Missile Systems Center, located at Los Angeles Air Force Base in El Segundo, California, is the U.S. Air Force’s center of excellence for acquiring and developing military space systems. Its portfolio includes GPS, military satellite communications, defense meteorological satellites, space launch and range systems, satellite control networks, space-based infrared systems and space situational awareness capabilities.
By Peter Steigenberger, André Hauschild, Steffen Thoelert and Richard B. Langley
Between Feb. 7, 05:02 UTC and Feb. 8, 12:30 UTC, 2017, all seven operational GPS Block IIR-M satellites were consecutively subject to short periods of unavailability. These official outage periods, when the satellite signals were set unhealthy and deemed unusable, were announced ahead of time through Notice Advisories to Navstar Users (NANUs). An overview of the outage periods and the corresponding NANUs for each satellite identified by their pseudorandom noise code (PRN) assignment and space vehicle number (SVN) is provided in TABLE 1.
Table 1. GPS Block IIR-M satellite outage periods and corresponding 2017 NANUs.
An analysis of the measured signal-to-noise-density ratio (C/N0) from several tracking stations of the International GNSS Service (IGS) indicates that the satellites’ transmit powers were increased during the outage periods. The effect is visible in the plots in FIGURES 1 and 2, which show C/N0 of the L1 C/A-code over time for satellite passes on the three consecutive days Feb. 6, 7 and 8, 2017.
Figure 1 shows the results for PRN 17 as tracked by a Septentrio PolaRx4TR receiver (USN8) located in Washington, DC. The pass on the outage day Feb. 7 is plotted in blue. Obviously, the receiver is configured to not track unhealthy satellites, since no observations are available during the outage period. However, a clear increase in the C/N0 is visible from about 50.5 dB-Hz before the outage to approximately 52 dB-Hz after the outage. The C/N0 level of the day before is similar to the level prior to the outage. The C/N0 level on the following day is very similar to the C/N0 after the outage, which indicates that the satellite continues to transmit with an increased power.
Figure 1. Plot of L1 C/A-code C/N0 over time for consecutive satellite passes of satellite PRN 17 (SVN 53) tracked by a Septentrio PolaRx4TR receiver located in Washington, DC, on Feb. 6–8, 2017. The satellite’s unhealthy period on Feb. 7 is indicated by the gray shaded area.
The plot in Figure 2 shows the same analysis, this time for PRN 05 and for a Leica GR10 receiver (KOUG) located in Kourou, French Guiana. This receiver continues to track the satellite during the unhealthy period. The distinct step in C/N0 is clearly visible shortly after the satellite is set unhealthy. Also, this satellite continues to transmit with increased power during the pass on the following day. The same observations as in Figure 1 and Figure 2 can also be made for all other Block IIR-M satellites and other receivers.
Figure 2. Plot of L1 C/A-code C/N0 over time for consecutive passes of satellite PRN 05 (SVN 50) tracked by a Leica GR10 receiver located in Kourou, French Guiana, on Feb. 6–8. The satellite’s unhealthy period on Feb. 7 is indicated by the gray shaded area.
The difference between the measured C/N0 before and after the unhealthy period is typically 1–2 dB-Hz depending on the receiver and the satellite (see TABLE 2). On average, a power increase of 1.5 dB with a scatter of ±0.25 dB among the various satellites is suggested by the measured data.
Furthermore, it may be noted that different receivers respond with a different change in C/N0 for a given change in transmit power. At the average 1.5 dB power increment, C/N0 changes between 1 dB and 2 dB are reported by the different types of receivers. This indicates manufacturer-specific algorithms for C/N0 estimation that impact the use of measured C/N0 as a reliable indicator of received signal power strength.
Table 2. Changes in C/N0 (dB-Hz) obtained from differences of days before and after the increase of the transmit power.
It is interesting to notice in this context that NANU 2017005 issued Jan. 19, 2017, states that “The 2d Space Operations Squadron (2 SOPS) periodically conducts configuration changes on GPS satellites to assess current capabilities, validate future capabilities and ensure continued interoperability.”
Furthermore, the Civil GPS Service Interface Committee Executive Secretariat released the following statement on Jan. 25, 2017: “Beginning 25 January 2017, Air Force Space Command (AFSPC) will conduct a limited duration test implementing an increase of the L1 C/A power level on the GPS Block IIR-M and IIF satellites (19 vehicles).”
However, no maintenance has been announced so far for any of the Block IIF satellites, and no obvious increase in the measured C/N0 could be found for these satellites. A repeated analysis for the Block IIR-M satellites on Feb. 22, 2017, confirmed that the L1 C/A-code power levels were still at their increased levels.
Measurements with the German Aerospace Center’s (DLR’s) 30-meter-diameter high-gain antenna at Weilheim, Germany, have been recorded to independently confirm the GPS Block IIR-M transmit power increase of the L1 C/A-code. FIGURE 3 shows the L1 spectral flux density for March 4, 2017 (blue line), and a previous measurement taken on Dec. 7, 2015 (red line). The sharp peak in the middle of the spectrum represents the C/A-code. A clear increase of the power in the measurement of March 2017 compared to Dec. 2015 is visible. Further analysis of the high-gain antenna data yields a power increase of about 2 dB.
Figure 3. L1 spectral flux density of PRN 29 (SVN 57) for Dec. 7, 2015 (red, normal C/A-code power level) and March 4, 2017 (blue, increased C/A-code power level).
However, the M-code flux density with main lobes near 1565 and 1585 MHz is reduced in March 2017 compared to Dec. 2015, whereas the P(Y)-code signal strength remains essentially unaltered. The total transmit power in the L1 frequency band is the same for both time periods. Therefore, the analysis reveals a redistribution of transmit power from M-code to C/A-code for the Block IIR-M satellite PRN 29 (SVN 57).
Authors Peter Steigenberger, André Hauschild and Steffen Thoelert are from the German Aerospace Center (DLR).
Richard B. Langley is from the University of New Brunswick and authors the monthly Innovation column for GPS World magazine.
RF optical solutions maker Foxcom has introduced a range of products to serve the GPS/GNSS repeater market.
Foxcom launched an Iridium repeater in September 2016 and is now offering advanced GPS/GNSS repeater solutions globally.
The firm’s repeaters have been designed to cover a wide range of commercial and military applications, such as:
aircraft hangars
time distribution in data centers
GPS distribution in tunnels
police and fire stations
manufacturing and test facilities
GPS L1 and GLONASS signals are passed through the repeater to the interior space. This means that satellite navigation devices will always receive a signal when indoors, eliminating any satellite acquisition delay when leaving the building.
Foxcom offers a choice of coax or optical solutions that have been optimized to meet the needs of customers worldwide, including.
Optical GPS/GNSS Repeater. Foxcom’s GPS/GNSS optical repeater solution is for retransmitting GPS/GNSS signals indoors. The repeater system provides seamless coverage inside a hangar or a large facility enabling the testing of navigational systems.
GPS/GNSS Distribution in Tunnels. Foxcom’s redundant GNSS Time Distribution System (TDS) ensures failsafe global satellite navigation signal transmission in tunnels.
GPS/GNSS Distribution for Data Centers. Foxcom’s optical redundant GNSS Time Distribution System (TDS) ensures failsafe synchronization in data centers by transmitting fully redundant GPS/GNSS signals. By deploying Foxcom’s optical GPS/GNSS link, networks of data centers at multiple locations can be accurately synchronized.
GPS Optical Link | GL7222. Foxcom’s Sat-Light/Gold L-Band Interfacility Link offers a high performance, alternative to conventional coaxial-cabled systems. The Gold GPS Link covers the frequency range of 1100 to 1600MHz and supporting both L1 and L2 GPS bands. The Gold Series GPS link is compatible with wide range of active GPS antenna and is equipped with voltage selectable GPS antenna powering.
GPS Repeater Kit. Foxcom’s GPS repeater solution is for retransmitting GNSS and GLONASS signals indoors. The repeater system provides seamless coverage inside a hangar or a large facility enabling the testing of aircraft navigational systems. The kit consists of an active repeater, indoor/outdoor antennas and 3 x 30 foot coax cable.
Coax-based Iridium repeater. Iridium satellite telephones are used all over the world. They generally can’t operate indoors, because the structure of the building blocks the ingress and egress of the signal. When it isn’t practical or safe to leave the building to make a call, a repeater system overcomes this barrier.
Iridium repeaters are used in a wide range of situations, including underground civil defense/military bunkers, oil rigs/ships, large buildings and any other underground facilities.
Foxcom’s coax-based Iridium repeater can be used when the distance from outdoor to indoor antennas is short. For example, when used in an aircraft hangar the ODU and IDU may be just a few meters apart. The cost of the coax-based kit is significantly lower than that of the optical version.
The new coaxial repeater system merges the ODU and IDU into one combined unit removing the optical fiber interfaces. The single IP65 repeater unit is roof-mounted and comes as a kit with antenna set and the required cabling.
Here’s a panorama in broad strokes across the range of GNSSs, garnered from top system spokespersons at the Munich Satellite Navigation Summit. It’s been several years since breaking news was aired at this annual late winter/early spring event, but it’s always good for a wide-ranging update, recalibrating levels, so to speak.
GPS. With 31 operational satellites (24 is baseline) and an estimated 3 billion receivers in use worldwide, what more needs to be said about the gold standard? Its best week ever for accuracy logged a signal-in-space performance average of 45.3 centimeter. The next-generation ground control system OCX “survived quite a struggle” and has emerged from Nunn-McCurdy breach, back on track and seemingly ready for future action. Or at least for future pre-certification tests. SV1 of the GPS III generation has completed all tests and is in storage, awaiting the first GPS III launch in spring 2018. SV02 and 03 are in assembly and integration, SV04 thru 08 are in box-level assembly, and 09 and 10 are on contract. Technical challenges with payload have been resolved.
(Click to enlarge.) Galileo satellite top-level block diagram. OHB Systems AG as prime contractor and Surrey Satellite Technology (SSTL) have teamed for production of the navigation satellites. OHB is responsible for the concept, the satellite platforms and the satellite-level inegration and test. SSTL supplies the satellite payloads and supports OHB on system level. OHB also supports the customers during launch preparation and in-orbit testing. (Image courtesy OHB)
Galileo. With 18 on-orbit satellites (15 operational), the European GNSS can be termed a coming thing. Performance statistics are based on only 11 of these satellites however; the four most recently launched in November 2016 are not yet included. Nevertheless, the system is logging 80-centimeter ranging accuracy. Eight more await launch: four in 2017, and four in 2018. The constellation is broadcasting the Open Service, the Public Regulated Service, and the Search and Rescue (SAR) signal. The SAR service will officially launch in early April — on April 6, because 406 MHz is the Emergency Position Indicating Radio Beacon frequency. Galileo has improved the historic SAR location performance from 3 hours to 10 minutes. The Commercial Service is still in preparation, and will be available in 2020. Spoofing is seen as a very real threat to GNSS overall by the Galileo authorities, as exemplified by the recent bloom of amateur spoofers encouraged by Pokemon go.
GLONASS. The Russian system will undertake three or four launches this year; one of them will be a triple-satellite launch. There have been several disruptions to efforts to decrease the offset between GLONASS system time and Universal Coordinated Time but the initiative perseveres. English versions of four system interface control documents (ICDs), to include the new CDMA signal, are promised for Q2 2017; Chinese versions are coming, too. Russian-language ICDs are available at glonass.aic.ru.
BeiDou. With the addition of three new satellites in the past year, China’s system is enjoying improved system performance. Hydrogen clocks are succeeding rubidium clocks, bring an order-of-magnitude improvement in timing accuracy. A BeiDou white paper was published last June, and a revised ICD appeared in November.
In the massive Chinese mass market, 30 percent of smartphones sold in China now have BeiDou capability; that’s out of a 700–800 million total. Huawei multi-function chip LX1101 is a key driver behind this. Unistrong has released a phone with RTCM input for professional use, blurring the line between mass and professional markets.
Six to eight satellites will be launched this year, and 10 to 12 in 2018. BeiDou is in a “very ambitious and aggressive race with time to complete the global system.”
ICG. The United Nations’ International Committee on Global Navigation Satellite Systems will meet in Japan in December of this year, in China next year, and in India in 2019. This can be interpreted as vigorous international interest and “a desire to advance and promote their respective systems’ visibility” worldwide. All pertinent documents can be found at unoosa.org.
EGNOS. The European Geostationary Navigation Overlay Service has two operational geosynchronous Earth-orbit satellites (GEOs) in operation, plus one in test and one in deployment, ready to swap in. It is extending its Ranging and Integrity Monitoring Stations (RIMS) to several new countries, notably Israel and the Ukraine. EGNOS.v3 is coming and will introduce dual-frequency (L1 and L5) service, and also Galileo with GPS, for multi-constellation corrections. The new system’s qualification is planned for 2022.
QZSS. This year, Japan’s Quasi-Zenith Satellite System will launch the second and third of the figure-eight inclined geosynchronous orbit (IGSO) satellites of the Michibiki type, to become operational in 2018. A GEO bird will also be launched. A seven-satellite system is the ultimate goal.
Among other announcements of note made during the course of the Summit, although not by the GNSS operators’ spokespersons:
(Click to enlarge.) Key features of the Galileo satellites.
• OHB, the Galileo satellite manufacturer, said its customer has decided to refurbish the clocks on eight satellites in preparation. “Satellite navigation is nothing but comparison of very precise clocks.”
• Airbus announced a new concept for train positioning integrity: “virtual valises” to correct train position that will replace or augment current trackside valises that are very expensive to build and maintain.
• Munich Aerospace (munich-aerospace.de), a public-private non-profit venture between DLR, the German space agency, Bauhaus Luftfahrt and two technical universities, will mount a Ph.D-level education and research program for 70 individuals, with candidates from 27 nations. This will be located in “the Bavarian Silicon Valley.” It will also undertake a global effort with several other organizations.
• One of the above technical universities, the Federal Armed Forces University in Munich, announced that it is investigating Lidar for potential use in an asteroid mining project for future space exploration. It also has underway initiatives concerning Lidar + GNSS and inertial + GNSS for autonomous vehicles.
Topcon Positioning Group has launched a new system for automated concrete paving — the ZPS system — with the new Z-Robot and Z-Stack sensor.
Using enhanced Topcon “millimeter GPS technology,” the ZPS system is designed to bring unmatched accuracy to concrete paving with a fraction of the hardware required for a traditional local positioning system.
The new Z-Robot is an advanced robotic total station with integrated Z-beam laser technology. The Z-Robot is designed to provide a hybrid function of high-precision, optically based vertical accuracy control and the convenience of Z-beam laser positioning to maintain that accuracy across the paver.
“The ZPS system’s self-leveling Z-Robot cuts setup time in half compared with previous concrete paving methods,” said Murray Lodge, senior vice president and general manager of the Construction Business Unit. “With traditional systems, you need multiple, expensive robotic total stations to control the paver at any given time and at least another complete set of instruments for downrange transition. With the ZPS system, only one Z-Robot controls the paver — increasing productivity and profitability, and dramatically lowering the cost of the solution compared to LPS.”
On board the paver, the ZPS system uses the new Topcon Z-Stack modular-designed system that seamlessly integrates GPS, optical targeting, and Z-beam reception into one unit by interlocking the required sensing technologies in one rugged “stack.”
“The Z-Stack sensor is revolutionary,” said Lodge. “It combines time-proven Topcon positioning technologies into one multifunctional, consolidated and complete system that provides better accuracies and more efficient paving than ever before. The system requires no separate base station and only one cable needed for power and connectivity.
“The system also offers a wider working area, with a range of up to 150 more feet than with traditional methods — minimizing instrument transitions,” Lodge said.
The solution also features configurable software, allowing the addition of support for GNSS and sensing.
According to the companies, Dragonfly NB1 leverages Ceva’s long heritage of low power DSPs and modem design and Astri’s experience in RF and IC design technologies. Dragonfly NB1 has the ability to reduce the time taken to get NB-IoT products certified and also provides low-power wide-area SoC designers with a flexible, software-upgradeable platform with key benefits in terms of die size and power consumption, the companies added.
The Dragonfly NB1 solution is enabled by a Ceva-X1 IoT processor and incorporates highly power-efficient multi-standard RF with embedded PA, LNA, DC-DC and DCXO technology for NB-IoT and GNSS (GPS and BeiDou). It is specifically designed to operate with embedded flash by incorporating an optimized low latency memory subsystem with a dedicated cache controller.
“In the coming years, NB-IoT will become the dominant technology for low power wide area connectivity,” said Michael Boukaya, vice president and general manager of Ceva’s Wireless Business Unit. “For most companies, understanding how to develop this technology is a daunting task. To overcome this, we have worked relentlessly with ASTRI to develop a complete solution from the ground up, that removes the design burden and allows SoC designers to add NB-IoT connectivity to their product designs. We’re extremely excited to announce this solution and demonstrate our leadership in IP for NB-IoT.”
Ceva and ASTRI have also teamed up with GMV, a major player in navigation systems and solutions, to offer an integrated GNSS solutions for smart devices with location tracking of logistics, assets, wearables and more. According to the companies, the GNSS IP is available as an add-on software that runs on the Ceva X1 together with the NB-IoT and leverages ASTRI’s GNSS RF IP that is embedded in the solution.
In early January, a new U.S. Department of Homeland Security (DHS) document appeared: “Improving the Operation and Development of Global Positioning System (GPS) Equipment Used by Critical Infrastructure.”
The document focuses on receivers used in critical infrastructure, with an emphasis on timing receivers. It provides owners, operators, researchers, designers and manufacturers with information to improve the security and resilience of PNT equipment across the spectrum of equipment development, deployment and use.
Specifically, its recommendations address:
installation and operation strategies that can be implemented for current equipment,
strategies that can result in more robust and resilient new and/or improved products based on existing technology and knowledge,
research and development that can lead to improved future capabilities.
It introduces clear definitions of different categories of threats and hazards, including the new term “data spoofing.” It recommends some creative ways to install receive antennas, such as using decoy antennas and obscuring the location of the actual antennas being used, presumably to foil some spoofing attacks. It also points out that modern GNSS receivers are computers, and need to be operated and maintained with good cyber hygiene, just like other computers.
The extensive list of recommended development strategies will challenge manufacturers while informing purchasers about the features they can seek in new equipment.
Implementing these recommendations will lead to increased competence — that is, equipment that is better able to accommodate imperfect or faulty inputs, intentional or not.
The document reflects the recognition that many reported problems or difficulties with GPS could be prevented or mitigated by improvements in GPS user equipment and how it is installed and operated. It is encouraging to see DHS taking steps to remedy this situation, and important that manufacturers of timing receivers, as well as critical infrastructure owners and operators that use timing receivers, follow through on these recommendations.
The document is posted on the website for DHS’ National Cybersecurity & Communications Integration Center, National Coordinating Center for Communications-Computer Emergency Readiness Team.
Robots are way cool. Anyone three or older knows that. And agricultural robots were among the first envisioned civilian applications of GPS. When Brad Parkinson went to Stanford in 1984, one of the earliest demonstrations he and his bright new students conducted was fully automatic GPS control of farm tractors on a rough field to an accuracy of 2 inches. Now it’s a bazillion global industry. See “Agriculture robots market projected to reach US$5.7 billion by 2024” for a few figures on that.
The market report underpinning that story contained a couple unquantified yet provocative assertions. Here’s one: Rural flight to the cities is a big force in this market’s growth.
“Progress . . . has primarily driven a growing number of people towards the urban areas and the suburbs. . . . This, in turn, has caused a twofold need for the incorporation of agriculture robots in several countries. Firstly, the growing global population — a lot of it being urban — is pressuring countries to increase food production while steadily reducing the hands available for the agriculture industry. Secondly, the overall land slotted for agriculture in nearly all countries is reducing, thanks to the burgeoning industrial sector and residential construction projects.”
I find this a bit chilling, a bit 1984-ish, and goodness knows we’ve got enough of that going on already. Will our future trips through the countryside, the shrinking countryside, take us through landscapes populated by nothing by smoothly chuffing engines? Will the term “bucolic” lose all meaning?
A second factor driving the agricultural robots market is “the increasingly accepted modes of corporate farming.” Now, I know that multitudes must be fed. Still, personally, I buy my food from small, local farmers as much as possible. It simply tastes better. That is indisputable. Arguments rage about whether it’s better for you; I believe that it is.
I hope the small farmers that my family and neighbors depend on benefit from GPS even though they don’t have huge expensive pieces of equipment. I’ll have to ask them next time I go on a visit. Meanwhile if any GPS and/or robotics manufacturers supply products to the artisanal, shall we say, as opposed to the corporate side of farming, I’d like to hear from you.
The logs contain highly detailed GPS positioning, drone battery life, camera activity and more, providing a vital record of flight activities often required for regulatory compliance and insurance.
Direct access to actual flight logs eliminates the tedious, manual data entry process for capturing flight data and enables drone operators to easily track and monitor their drone flights for regulatory compliance, insurance and fleet maintenance.
DroneDeploy’s more than 10,000 users in 130 countries can access logs of their DroneDeploy mapping flights. Leveraging their actual flight log data with DroneDeploy’s partners enables businesses to:
Automate logging and recording of all drone flights for compliance and insurance purposes
Monitor equipment performance to recommend preventative maintenance
Explore trends in flight characteristics to define best practices
“Many large companies and enterprises are looking to scale their drone program and do it efficiently,” says Jonathan Evans, CEO of Skyward. “Now, with access to DroneDeploy flight logs, Skyward customers can manage flight information across their entire fleet.”
Other solutions on the market today typically require a high cost investment and lock businesses into working with a single drone software vendor, DroneDeploy says. DroneDeploy’s offering enables businesses to select what works best for them from a selection of industry leading drone compliance, insurance and fleet management partners. This highlights DroneDeploy’s approach to addressing the needs of the commercial drone market by developing a best-of-breed offering with ecosystem partners.
The Oregon Department of Transportation (ODOT) is embracing the growing trend in highway construction to go “stakeless” and push to full 3D design.
With more contractors using automated machine guidance applications, ODOT’s construction personnel are being asked to inspect projects with fewer stakes and visual indicators for line and grade. Employees are seeking to use the same data and information to determine line and grade when building or fixing stretches of road.
ODOT inspectors Jorge Jimenez and Mike Stennett at Multnomah Falls, preparing for a night-time paving operation. (Photo: Chris Pucci)
To address this need, rugged tablet maker DT Research worked closely with ODOT to design purpose-built Inspector Positioning Tablets that run GPS locating and 3D modeling applications, and take advantage of the Oregon Real-Time GNSS Network.
“MicroSurvey Field Genius surveying software is used to read XML files directly, allowing the inspector to work with the same files that the contractors received from the roadway designers,” said Chris Pucci, ODOT Construction Automation Surveyor.
The tablets enable ODOT to fully use its knowledge of the Oregon Real-Time GNSS Network and expertise in survey-grade RTK GNSS to achieve accuracies of +/0.05 feet.
The model DT391GS tablets have 9-inch touchscreens. The tablets can be used as handhelds or with an external antenna and pole. ODOT purchased one of four GNSS options offered by DT Research for the DT391GS tablets. The options enable inspectors and construction crews to employ a combination of GPS locating and 3D modeling to guide construction workers.
The goal is to allow the inspectors to make the same checks they would have made if there had been traditional construction staking on a project, not to make inspectors into surveyors, Pucci noted.
A one-day training is provided to train construction personnel before they are issued a tablet. “The tablets have been very well received by our construction inspection personnel,” he said.
The tablet project is now in the pilot phase with 20 tablets deployed to eight construction offices and more than 70 construction personnel having been trained. “We also just placed an order for 22 more tablets for the upcoming 2017 construction season,” Pucci said.
The report was commissioned by Innovate UK, the UK Space Agency and the Royal Institute of Navigation. It followed from the January 2016 accident referenced earlier, in which an error in the GPS signal from certain satellites, triggered by the decommissioning of one of those satellites, brought a number of key industrial servers to their knees. The episode lasted 12 hours.
The document focuses on receivers used in critical infrastructure, with an emphasis on timing receivers. It provides owners, operators, researchers, designers and manufacturers with information to improve the security and resilience of PNT equipment across the spectrum of equipment development, deployment and use.