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Home arrow Archives   The American Surveyor     

You are the Committee: 50th Meeting of the Civil GPS Service Interface Committee Print E-mail
Written by Gavin Schrock, LS   
Friday, 22 October 2010

You should have a say in the matter
Aging satellites, potential delays in modernization, potential jamming hazards… Do you want a say in the matter? You should have a say in the matter – the state of GNSS services does affect your profession and what you do as a land surveyor whether you are a practitioner of GNSS surveying or not. The national geodetic reference framework is nearly wholly dependent on GNSS as well as your state and local references. With this much at stake wouldn’t it behoove the surveying community and individual surveyors to demand a seat at the table in matters of the health and viability of the GNSS services? There is a mechanism, and it is much easier to participate than you might think.

Shortly after the last of the Block I GPS satellites were launched in 1985 and the constellation was pronounced operational the first meeting of the CGSIC (Civil GPS Service Interface Committee) was convened. Since before the inception of GPS, there was recognition of and full expectation that the civilian uses and user segments would grow and realize benefits increasing beyond the imaginations and technologies of those early days. The CGSIC was formed by the Coast Guard and Department of Transportation to be THE ONE AND ONLY direct forum between the end users and those parties managing, designing, operating, and upgrading the constellation. These twice yearly meetings are not smoke filled back room affairs; these are held as completely open public forums.

September 20th -21st, 2010 saw the 50th CGSIC general meeting in Portland Oregon. Like other CGSIC meetings in recent years it has been held preceding an annual ION (Institute of Navigation) conference; a logical choice as many of the key shepherds and policy wonks for the constellation as well as end user industry types are already in town for the high level ION educational and scientific forums (more about ION later).

Photo caption: “You are the Committee” – an energizing keynote address by Captain (USGC ret.) James Doherty (left), Senior Analyst, Institute for Defense Analyses.

The keynote address for the two day CGSIC was given by Captain (USGC ret.) James Doherty, Senior Analyst, Institute for Defense Analyses who has been in involved in the leadership of CGSIC for many of its years. Capt. Doherty spoke of the history of CGSIC, ups and downs in attendance and influence, even of a point over a decade ago where his past boss at the USCG considered pulling the plug. But a lot has changed since then; end user communities have become much broader, even consumer based, international, and much more vocal.

How does the committee work? It is a committee of those who participate; the constellation shepherds from the military like the USAF GPS Wing, policy types like those in the National PNT (Position, Navigation, and Timing) Coordination Office, manufacturers, academic researchers, and end users… anyone can participate. As Capt. Doherty stated “You are the committee”. He went on to point out (and perhaps chide some of the government presenters) that the CGSIC was not meant to be a one-way street, not just a series of dry status updates. It is to solicit, gather, and respond to feedback and suggestions from the civilian user communities.

Attendance was up from previous years, and due in part to the call to action set by Capt. Doherty the energized crowd offered many an insight and lively debate. Evidence of how the CGSIC actually does affect change was in the addressing of an action item from the 49th meeting. A lot of discussion last year on the state of NANU’s (Notice Advisories to Navigation Users) issued by the Coast Guard, Air Force and others was addressed by a report from Hank Skalski, Civil Liaison to the USAF Space Command, on the specific changes made in readability, frequency, and text formats; those asked for by end users.

Jamming
Among this year’s hot topics was the subject of intentional and unintentional jamming. An example was given by Leo Eldridge of the FAA where one of their LAAS (Local Area Augmentation Systems) base stations was too close to a turnpike, and the truck drivers who have purchased little cigarette-lighter ‘privacy jammers’ to cover their tracks had registered a handful of interference incidents. These little jammers can be found for under $100 online and while in many ways completely illegal to operate, there are still no completely clear answers as to how to control their manufacture, distribution and possible use. Also, just how much these would affect a survey rover has yet to be completely tested. It is less likely that the effects would be so subtle as to give you a false reading that you would not otherwise detect. It would be more likely that you would experience a loss of service; a failure to fix or maintain fix, or that a jammer in a passing vehicle would compromise for such a short duration that it may not be detectable as such.

The potential for jamming, both intentional and unintentional is a scary subject, and a national plan to deal with this has been well under way for many years. The U.S. Interference Detection and Mitigation Plan (IDM) is being implemented by the Department of Homeland Security. The types of possible interference include the unintentional from such sources as large communications transmitters, navigation aids, harmonics from a wide variety of even commercial radio transmitters, and then the intentional like the ‘privacy jammers’ or even (unrealized as yet) terrorist jamming. While this would be a good subject for a full article, suffice it to say that there are a lot of sensors and people watching for these types of interference and as yet there have been only a scant handful of instances of any kind. What can a surveyor do or even what should they do? The nature of the small scale ground based jamming of any kind makes it very unlikely that there would be a direct effect that would be indistinguishable from other sources of poor fix or quality. But for large scale and fixed sources of in-band interference, like say some suspected large radio transmitter in the area of your work there are some options for detection.

This matter of in-band interference detection was the subject of one of the manufacturer perspectives presented at this year’s CGSIC. Javad Ashjaee, CEO and President of Javad GNSS joked that he would not use his presentation to brag about his new products (but we could see this coming). He examined the nature and sources of in-band interference for the crowed spectrum in which GNSS resides. Typically detection of such was only possible through the use of sophisticated and expensive (e.g. $30,000+) spectrum analyzers. He did show examples from the new in-band interference detection application that is an add-on feature for his new (go figure) VS rover. Javad was very clear in stating that the capabilities of this application does not address say the military-grade hazards and may only detect interference from certain fixed sources, but that this is a first in a rover product, and a great step forward.

Photo caption: On the hot seat – Presenters from offices of the national PNT policy and GPS operations like the Air Force, State Department, Department of Transportation and Coast Guard sat for open grilling by the audience after each group of presentations.

The Sky Continues to Fall?
A perennial hot topic is the health, modernization, and long-tem viability of the GPS constellation. As with every year, the GPS Wing provides an outstanding briefing on just how well operated and maintained the fleet is. (And  a subsequent conference call set up for the media as a response to a recent GAO report pointing at risks to the GPS program was given on September 24th… see sidebar). Questions from the audience lead discussions of how causes for past delays in deployment of new birds have been fixed even though the requirements have been increased. Kind of like the struggles of Sisyphus; the GPS Wing overcomes old problems, only to have the bar continually set higher. The underlying message is that the constellation is at a record 31 birds, it is healthier than ever before, all performance is far above spec, and that the minimum 24 is not in any immediate danger. There is a new plan being implemented that has been dubbed “the expandable 24” where some birds are being shuffled around to have extra birds in critical slots, a example of a test over Afghanistan  showed how the “expandable 24” could actually improve coverage over the standard 24 configuration. The shuffling of the birds should be complete by January of 2011.

Sidebar: GPS Wing Responds to GAO Report
September 24th, 2010 - A teleconference was arranged by the USAF GPS Wing to respond to a GAO (Government Accountability Office) report titled “Global Positioning System: Challenges in Sustaining and Upgrading Capabilities Persist.”  Those that signed on to the teleconference were almost exclusively press, mainly media that most typically follow aerospace topics like Aviation Week, Air Force Times, and Inside the Air Force, but also more mainstream media like Bloomberg Television. This broader interest, especially by financial media shows just how much commercial use and dependence on GPS there is. Colonel Bernard Gruber, commander, GPS Wing and Colonel David Buckman, AFSPC command lead for PNT very clearly put perspective into what they both viewed as “a factually correct but overly pessimistic report”. In their view, elements of the GPS program which have in the past been factors in delays have been over-emphasized in the evaluation of future risks. “Time to look to the future  rather than the past” stated Col. Gruber. The press seemed very satisfied with the characterization of the report as merely “assessing possible risks” as opposed to predicting any certainties. The sky is not falling.

For many, the sky continues to fall no matter how much they hear otherwise. Heightened awareness often breeds heightened (or hyped) panic. With more people there are using GNSS and the increased dependencies by some user segments, of course there will be increased sensitivity to even the slightest risk factors. Are there more earthquakes than in the past or do we just hear about them sooner and more frequently? Are they hiring TV stars with more wrinkles or do our HD and Blu-Ray just show them clearer? Is the constellation really at higher risk than before or is the GAO scrutinizing ever more unlikely scenarios than before. There seems to be a cottage industry of slow-news-day GPS panic-merchants. It was explained by the GPS Wing and the PNT Office that compromises in service if the constellation were to drop below 24 would be area dependent and would only greatly affect high precision users in those regions/time periods, but furthermore that to drop below 24 the modernization program would have to fall a full 2 years behind schedule (and some elements are several months ahead of schedule). Considering the astounding commercial, financial, and military dependencies on GPS, are we to believe that anyone would allow the program to fall more than two years behind schedule? If that were true then we might have bigger worries than the GPS constellation.

Space weather and the solar max on the other hand is a concern where the magnitude, effects and outcomes are not entirely clear. I ran into Joe Kunches, scientist with the NOAA Space Weather Prediction Center who on the one hand was happy to report that the run up to the expected 2013 solar max has been a lot calmer than expected, but on the other hand admitted that it also made it challenging to study the effects. More than one ‘old timer’ said they survived a previous solar max, so not to panic. Folks like RTN operators have not been reporting much direct problem with end users correlated with the rise to the max, but there are still a few years to go, and a lot of unknowns.

Of course there was talk of SVN49, that ‘test-bed’ satellite for L5, which has been set as unhealthy to users due to a form of internal multipath. The CGSIC and other entities have solicited feedback from the users/manufacturers as to what steps to take to correct this. After weighing the widely ranging suggestions a very careful but complex plan has been developed to coax SVN49 back into a healthy state. Karl Kovach, technical advisor with the GPS Wing stated that this plan will take about four years.

NGS CORS Forum – New Kids on the Block
This was the first National Geodetic Survey CORS Forum under the helm of Giovanni Sella (taking over for the retired, but still very much involved Richard Snay). Three presentations in the forum were related to the NGS goal of aligning the national reference framework more tightly with that of the international ‘global’ framework; ITRF et al. In the first presentation Sella noted that the NGS strives to be a more active partner in the activities of the IGS (International GNSS Service) a voluntary international cooperative that uses an array of scientific instrumentation to perfect and update ellipsoids and other geodetic elements. The NGS will start by officially upgrading and adding a few dozen CORs to the IGS array.

Photo caption: NGS CORS Forum Presenters: Jake Sullivan, Giovanni Sella, Andria Bilich, and Bill Henning demonstrate how much change to typically expect between NAD83-CORS96 and the upcoming NAD83-CORS96A.

Jake Griffiths, of the NGS Spatial Reference System Division and new face too many gave an explanation of the computation leading up to the adoption of NAD83-96A which will be phased in to replace NAD83-CORS96 in the national reference framework. This move will hopefully remove some discrepancies seen in the way the older system works and will effectively be no more than a few centimeters change in most of the US (or less) but that it might be the Epoch changes in some regions that may end up showing more dramatic shifts between legacy published values and new values. This really warrants a full article (and I wish the NGS would pen one quick before this starts rolling out in early 2011). There will be an overlap period where 96 values will be available alongside 96A values (think OPUS et al) but get ready for change.

I am afraid to open a big can of Pandora’s worms, but there were aspects of the 96 to 96A migration that were only briefly touched upon that have more to do with how individual surveyors and even states may have to adapt to the changes. What NGS is NOT going to do is perform a full readjustment to provide updated published values for all the passive marks in your state. The dream of having the active and passive control systems be entirely in sync has rarely been fully realized in any region of the U.S. (or even in other parts of the world). Surveyors would love for their GNSS observations to match published passive control every time forever amen without any localization, but the earth changes and so does the reference framework. While many have found ways to deal with any existing differences between the passive and active (e.g. localization, applying velocities, or observing/updating/re-publishing) there are many that have not, and  changes like the 96 to 96A will be met with no small amount of consternation from some. A very good practical suggestion from Sella and the team was for local action to select an array of existing marks for duly constrained re-observation to determine just how much the of a shift 96 to 96A will have in your specific regions; these can also serve as localization marks.

Another move to improve the quality and tightness of the reference framework and to be more in line with the scientific community and IGS is to switch over to absolute antenna models (as opposed to the relative antenna models we are familiar with from the NGS). Andria Bilich of the NGS Geodetic Research Division explained how the process of developing a relative model is a simple baseline comparison, and that the absolute modeling is done with a robotic arm in a more comprehensive all around (literally) approach. Andria showed graphic examples of how a modern geodetic antenna may have a fairly consistent model across its entire body, but that some older simple ground plane and other antennas may have lopsided or otherwise inconsistent models. The NGS plans to keep the old relative models available but that almost without exception all new models would be absolute. Many RTN operators have moved to absolute models already, and the transition should not be problematic, but it will be another element that post-processors and other high precision GNSS users will have to be aware of.

Bill Henning, the NGS Real-Time Networks guru reported that the long awaited guidelines for Real Time Networks is being edited by none other than Dr. Snay and we should see something in print in early 2011 if not sooner.

But the Rest of World Likes GPS
It is no surprise that an all afternoon International session of the CGSIC was one of the most well attended. There is a certain irony that there are more users of the U.S. GPS constellation internationally than in the U.S. But also as other constellations continue to develop or are modernizing that the CGSIC is a key venue for providing program updates and to also solicit end user feedback for these constellation providers as well.

The understandably happy Hiroshi Nishiguchi of the Japan GPS Council reported on the successful launch of the first of the planned 3 bird GPS compatible quasi-zenith constellation (a very innovative highly elliptical orbit constellation that will sling 3 satellites in a sort of figure-8 over Japan and the pacific putting birds in the very desirable sky-view directly overhead for urban canyons and other narrow sky conditions). He also said that the timeline for the launches satellites 2 & 3 will be decided by January of 2011. This first QZSS satellite was nicknamed “Michibiki” or “leads the way” by nationwide vote. The launch got a lot of good press in Japan, and the event was celebrated with exhibitions, school science fairs, bottle rocket contests, and online educational and kids activities. Wow, and in contrast the U.S. press seems hell bent on slamming GPS and predicting its demise.

The Glonass constellation keeps rapidly growing and modernizing. In a summary by Sergey Revnivykh of the Russian Federal Space Agency, he spoke of 26 birds currently in orbit, 20 of which are operational plus two spares, 3 in commissioning phase and 1 in repair. With another multiple launch before the end of the year this means that Glonass hits its optimal constellation of 24 very soon. There have been characterizations by many that Glonass satellites are cheaper to deploy because “they don’t last as long”; Sergey’s talk shed light on how this view might have been formed. Indeed the Glonass 1 birds, that were not designed to last but a few years, and are now all defunct, but that newer birds have 7 and 10 year design lives (much the same as GPS), and we all know how much longer than expected some of many of those have lasted. One comparison of quality is URE (user ranging error) which is what could be expected for completely autonomous single frequency use in the effective areas of coverage. In the 90’s even the GPS constellation URE was more than 2 meters (and is now reaching closer to 0.5m, due in part to the outstanding work done with the clock component). Sergey has happily reported that Glonass URE is now below 1m, and improving all the time. In the next few years the Russian Federation will start working with CDMA (code division multiple access, like GPS) as an eventual possible replacement for FDMA (frequency division multiple access, that they currently employ which limits the capabilities of their constellation), but that even after CDMA is fully adopted (which is still many years away) they will keep FDMA running as well for at least 10 years. So don’t throw away your old Glonass capable gear just yet.

No news from Galileo. But it was pointed out by a number of folks that if/when fully deployed and healthy and as currently envisioned Galileo could be best poised of all the constellations to achieve the 0.1m URE multi-band-uncorrected dream.

ION - GNSS to Infinity and Beyond
An ION (Institute of Navigation) conference is not a surveying conference, but it does hold items of interest and educational opportunities for surveyors and the manufacturers of the gear they use. But it is also aimed directly, or indirectly at many other end user segments of GNSS (and many other forms of navigation, but mainly GNSS) like the folks that put GNSS in missiles, UAV’s, ships, containers, trucks, lions, and tigers, and bears. CGSIC is held just prior to an ION conference, and ION in contrast is a much larger, for-fee event with panels and seminars that drill down deeper into the inner working of GNSS research and manufacturing than the average end user would imagine.

It is easy to get overwhelmed by “deep-geek” at ION. There was a Surveying and Geodesy Track, but with sessions like “Detection of Millimetric Amplitude Periodic Displacement Using One GPS Receiver” many of the session speak more to the academic and research side. These subjects are valuable and may lead to improvements in the gear that we may eventually use. There were a few gems like “GNSS handheld with Internal Antenna: What Position Accuracy Can One expect?” (Zyranov, Artushkin, et al w/Ashtech), and “Development of a Tightly Coupled INS/GPS Sensors Fusion Scheme Using Adaptive Kalman Filter” (Yao, Chen, et al w/Cheng Kung University, Taiwan) are quite a mouthful but may have direct application to our daily activities in the not too distant future. An interesting perspective on the modernization of reference frameworks was “WGS 84 Modernization” (Wiley, Wong, et al w/the National Geospatial Intelligence Agency); the NGS is not the only agency wrestling with these subjects.

The fun part of ION is the exhibits hall – a sort of “gee whiz” showroom. This year the floor space winner was Javad GNSS, but with many other huge displays from not only the GNSS manufacturers surveyors would be familiar with but more so the OEM and test equipment manufacturers. Ashtech is again a name seen among these displays. After many years and many name changes (Magellan, Thales) the OEM, surveying, and mapping gear manufacturer has returned to the original name. I spoke with Olivier CASABIANCA Product Marketing Manager – GNSS Boards and Sensors for Ashtech and he said that the name change has been met with great enthusiasm; there has always been great name recognition within user segments like science and academia.

As Ion is one of the events where new products are often rolled out, Olivier was pleased to offer up the new Ashtech Mobile Mapper 100, which adds full dual frequency to the lightweight handheld Mobile Mapper line. In line the trend we are seeing in the handhelds market; dual frequency, network capable, small and lightweight units coupled with external antennas are really bringing what we would consider to have been strictly survey grade precisions to what would have traditionally been seen as mapping grade devices. This is understandably scary to some folks, but the reality is that these units are here and are becoming more reliable affordable all the time.

A Committee that Writes Standards
The RTCM (Radio Technical Commission for Maritime Uses) sub group dubbed SC-104 also holds one of their meetings (more like a think tank) coincident with CGSIC/ION. This committee is the international body that develops standards for things like the GNSS correction formats for broadcast (e.g. RTCM 2.3 RTCM 3.0, NTRIP, etc). Dr, Georg Weber of the German Agency BKG (and one of the founding fathers of NTRIP) was happy to report some progress in two key areas the RTCM committee has been working on.

The upcoming version of Rinex is being designed to accommodate all of the message types (e.g. for all constellations) also to be accommodated in an upcoming version of RTCM 3, so finally there will be static and broadcast versions compatible. Georg said the details have been agreed upon but that now there is just a lengthy voting process to endure. Another development is that of a proposed “states based” approach to GNSS corrections. This subject warrants a completely separate article and is at first a bit hard to get ones head around, but imagine no longer transmitting observations, but rather correctors alone from multiple sources (i.e. clock and orbit correctors from an international array and only iono-tropo from the local networks), all on low bandwidth and perhaps via alternate communications methods. Cool stuff in the works.

The Labyrinth of PNT Policy
The decision matrix of Positioning Navigation and Timing policy is much more complex than that of GPS operations; folks in the GPS Wing do wonders with what resources they are handed. But just how and by whom the seeds of any new or bold initiatives could be sown is quite unclear. Most of the PNT policy crowd are listening earnestly, though some could use a Dale Carnegie lesson and be reminded what Capt. Doherty said about the dialogue being a two-way street. A few questions went unanswered like “Will the US ever entertain a quasi-zenith system like Japan?” and “Will we consider raising our nominal constellation to be above 24?” – Response to these fell into bureaucracy –speak, but for the most part other questions were answered clearly and directly.

Photo caption: Karen Van Dyke (left), Department of Transportation and CGSIC Chair –key player in many of the PNT policy related committees, panels and advisory councils.   Many consider Karen as the face of civilian GNSS and PNT.

A power point slide shown every year of the PNT matrix is so complex that it was even borrowed by the Russians to show humorously how complex their matrix is as well. There are so many advisories and liaison roles that it makes one wonder if anyone has actually been empowered to make the hard decisions. On the positive side, there are key players that have been around as a consistent voice for PNT and GNSS concerns. Karen Van Dyke, Department of Transportation and CGSIC Chair is involved in so many of the PNT policy related bodies that many have come to consider her as the face of civilian GNSS and PNT. Like Karen, there are many dedicated and capable people keeping an eye on the program on your behalf, many of these are perennials at each CGSIC. Highly consider attending or having representatives from your surveying association a meeting in the near future, and get to know these folks first hand. And speak up! You are on the committee!

 
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