GPS World

Category: Opinions

  • Out in Front: GPS World, 20 Years Young

    GPSW_20th_LogoThis magazine, the very one you hold in your hand or peruse digitally, hereby celebrates its 20th birthday. Hooray!

    Since its inception in 1989 and first appearance in the public eye in 1990, GPS World has provided — and continues to provide — technical and business information on global navigation satellite systems (GNSS) to engineers, product designers, manufacturers, researchers, system developers, executives, and high-level managers around the world who incorporate global positioning, navigation, and timing (PNT) technologies into their corporate strategies, operations, and product offerings to maximize profit and performance.

    Many things have changed since our birth: changes in the world, changes in GPS itself and now in GNSS, and changes in this magazine.

    The book has repositioned itself over the years from its early focus on applications to the present comprehensive yet detailed grasp of design concepts at both the space system and integrated circuit level.

    We can still say, as Glen Gibbons wrote in the inaugural issue, “Perhaps the most remarkable thing about GPS today is the enthusiasm that we find

    everywhere among people involved with the field. We want to share that enthusiasm with our readers. GPS — our world and welcome to it.”

    Double-Decade Insights

    Langley_new-mug_REV_lmRichard Langley: in the fall of 1989, GPS World’s founding editor, Glen Gibbons, approached Dave Wells, Alfred Kleusberg, and me — faculty members in the then Department of Surveying Engineering at the University of New Brunswick — about editing a “technology/product development column” in a new magazine. Since readers would have marked differences in their knowledge and expertise in the GPS area, “the column should deal with issues that have broad application and interest and are presented in terms that are accessible to as wide a range of readers as possible,” he wrote. The column was to be called simply Innovation.

    We decided that Alfred Kleusberg and I would manage the column, with Dave Wells serving as one of the inaugural members of the magazine’s Editorial Advisory Board. I took over sole responsibility for the column in 1997.

    Many Innovation columns have been tutorials including the one in the very first issue of the magazine. Written by Dave Wells and Alfred Kleusberg and titled “GPS: A Multipurpose System,” it used three different positioning scenarios to explain how GPS could provide positioning accuracies all the way from a Selective Availability-constrained 100 meters down to the sub-centimeter level. It also outlined GPS’s ability to determine platform attitude with multiple antennas and its use for accurate time transfer.

    The Innovation column has run continuously in every issue of the magazine except for August and December, when it gives way to the Almanac GNSS information pages. Next April’s column will be the 200th!

    Ed Aster, Founding Publisher: 20 Years Ago, GPS World almost didn’t happen. The idea of a magazine focussed on an unknown technology shrouded in military guise was turned down by 10 publishers before the idea was thrown at me while developing our international offices in Chester, England. It immediately made sense, as long as you had long eyes. A technology that has changed the world almost as much as the invention of the telephone. Who woulda thought. GPS leads the world and allows all countries to benefit from its quite simple premise, “Where am I?”

    GPS World: That Was Then

    During the last decade of the 20th century, the U.S. Global Positioning System achieved full operational capability. Prior to and after that key 1995 event, the technology saw active use and growth, primarily in the fields of surveying, mapping, and high-precision positioning. The technology most often took the form of a GPS receiver, frequently a stand-alone box, although active research and development into smaller form factors and integration with other technologies began.

    A 1996 Presidential Decision Directive reiterated GPS’ global availability for peaceful use. Russia’s GLONASS became irregularly active.

    Marking the practical — that is, the true — start of the GNSS era, the first integrated GPS+GLONASS RTK surveying system appeared in 1997: the GG-24 from Ashtech. The first GPS IIR (for replenishment) satellite rose that year, proving that satnav was not only here to stay, but to improve.

    Europe’s Galileo became a topic of earnest discussion.

    Double-Decade Insights

    McNeff_Jules_boxJules McNeff: Twenty Years ago, GPS was just a promise. The first Block II satellite was not yet a year old. GPS was known to only a few. It had not contributed to victory on the battlefield; it had not revolutionized earth science nor changed the way businesses and people conduct their daily activities. Now it has done all of that. It has awakened a global awareness of precise and ubiquitous position and time and of their value as essential elements of every human endeavor.

    I look forward to its next 20 years with the same anticipation and excitement I felt then.

    GerardLachapelleGerard Lachapelle: The Launch of the Block II satellites, starting in February 1989 after a hiatus of more than three years, was the most remarkable, exciting news of the time. By January 1990, six satellites had been launched with four more to come throughout 1990, an impressive accelerated schedule that had a major impact on equipment manufacturers, technology, performance, and users. It accelerated investments in research and development, and in long-term planning of major users and suppliers of positioning services.

    GPS would be a reality! The world has never been the same since!

    First Advertisers

    These companies advertised in the inaugural January 1990 issue — and we thank them!

    Three Full Pages

    • Ashtech

    Two Full Pages

    • Trimble

    Full Page

    • McDonnell Douglas
    • Magellan
    • Geodimeter
    • Wild Leitz
    • Interstate Electronics Corp.
    • Ball Aerospace
    • Oscilloquartz
    • Navstar
    • Stanford Telecom
    • Plessey/ITT
    • GE Astro Space
    • Odetics
    • CAST
    • ITT Defense

    Fractional Ads: Holden GPS, Sensor Systems, Racal, Alcatel, FTS/Austron, Allen Osborne Associates, Datum, McIntosh & McIntosh, Intermetrics, Piezo Crystal, Van Martin Systems, Navtech Seminars, GEOSurv.

    Map these companies onto their present names/ownership and enter to win the editor’s Happy Anniversary to Us Prize! Send your answers to [email protected].

    GPS World: This is Now

    During the first decade of the 21st century, the GPS industry entered early maturity and saw action in an ever-increasing number of fields: avionics, transportation, wireless communication, burgeoning consumer devices, and location-based services. Emphasis in product design shifted to the board and chip level, and GPS chips began “disappearing inside the application,” going inside other boxes fo
    r integration with other technologies.

    GLONASS declined, then rose again; Galileo got underway in fits and starts; international regional augmentations began.

    GPS World held its first Summit for 1001 GNSS VIPs with a top-level panel during the 2002 ION-GNSS conference, and a second Summit in 2004. It became the Leadership Dinner in 2006, with a Great Debate in 2007, a GNSS Election in 2008, and Brad Parkinson’s “True History of the Origins of GPS” in 2009. In each case, proceedings were subsequently shared with all our readers.

    The magazine became more than a magazine, redesigning its website to track developments in ever-diverging industry sectors, and launching e-mail newsletters focused on these specialized interests, followed by discussion forums, webinars, video interviews, job listings, and more.

    Double-Decade Insights

    ashkenazi_vidal_boxVidal Ashkenazi: As a geodesist, I consider GPS as the natural follow-on to satellite triangulation-trilateration and Transit Doppler (in the 1960s), when navigation and timing were added to straight positioning, and geodetic concepts of accuracy and reliability (renamed integrity) were adopted. We still had some difficulties in convincing the navigation community of the need to adopt a precise geodetic coordinate system (like WGS84), instead of just latitudes and longitudes.

    The imposition of Selective Availability led civilian ingenuity to come up with differential GPS, carrier-phase, and RTK. Who could have predicted in the 1990s that countless GPS applications would develop, benefiting business, governments and citizens everywhere?

    StephenC_BOXStephen Colwell: I started GPS World back in 1989. With a $1,200 investment and business plan in hand, I struggled through 43 investor presentations until finally receiving an approval nod for funds to launch the magazine. What I remember most during these times was invariably a potential investor would say “Now explain this to me again — what is GPS, and why does it need a magazine?”

     

    LONG HAULERS
    These memoirs come from founding members of our Editorial Advisory Board who still serve in that capacity! Jules McNeff is now vice president, strategy and programs, Overlook Systems Technologies; Gérard Lachapelle is professor and CRC/iCORE chair in wireless location, Department of Geomatics Engineering, University of Calgary; Vidal Ashkenazi is CEO, Nottingham Scientific Ltd. Other advisors still on board from that first issue are Paul Cross, Larry Hothem, William Klepczynski, Keith McDonald, and Brad Parkinson.Richard Langley is, as ever, a professor of geodesy and geomatics at the University of New Brunswick; Ed Aster is a vineyard owner and entrepreneur in New Zealand; Stephen Colwell writes a monthly e-mail column on the Consumer OEM sector; Glen Gibbons is a publisher in his own write, familiar to many readers.

    GPS World: Behold the Future

    Alan-CameronIn this nascent decade, the GNSS industry will enter its full maturity as truly an indispensable utility for everyday life, at individual consumer, industrial enterprise, and government organization levels. Multi-technology circuitry, which now integrates positioning with other capabilities on a single chip, will only continue its astonishing march.

    Galileo and GLONASS will achieve their promise, and Compass will join the family, forming together with GPS a veritable system of systems with highly accessible and accurate coverage and availability even in challenging environments. GPS itself will modernize, strengthen, and expand its considerable capabilities.

    As ever, GPS World will be there, up close and personal with the technology and the business, providing eyewitness accounts by researchers, product designers, program managers, and end users.

    The magazine will continue serving its international readers and advertisers, accomplishing its mission through an integrated information system of print, e-mail newsletters, websites, webinars, and videos, all communicating critical intelligence to decision-makers and technical experts.

    GPS World’s media platform, designed for and dedicated to industry’s use, is a searchable, application-specific knowledge base of GPS/GNSS-related technologies that is mapped to the markets and needs of the community’s core purchasing audience.

    Despite its name — and names may change — the magazine has never limited itself to coverage of the U.S. Global Positioning System. We chronicle the development of all GNSS: Galileo, GLONASS, and Compass; of augmentations WAAS, EGNOS, MSAS, NDGPS, QZSS, GAGAN, and GRAS. We track the integration of GNSS with other PNT technologies, such as inertial, laser, Loran, and radio frequency fields such as wireless communications, RFID, Bluetooth, ultra-wideband, and others.

    While busy writing and talking, we are also busy listening. We encourage online comments to articles appearing at env-gpsworld-integration.kinsta.cloud. We’ve started one technical discussion forum, Tech Talk, and plan to have another, on chip and circuitry design, flying within months. We administer a LinkedIn network for GNSS professionals to communicate interests, leads, queries, referrals, and open positions; our Facebook page enables members to create unique user content to build meaningful and resource-full discussion.

    We have unparalleled personal reach in every industry sector. You’ll find one or more of GPS World’s dozen correspondents and business development consultants at every important technical and business conference. Come right up and give us a piece of your mind. Please.

    GNSS — your world. We feel privileged to play a key part in it. — Alan Cameron, Editor-in-Chief

     

     

  • Letters to the Editor: Smartphone Revolution

    Nice article on “The Smartphone Revolution” in the December issue. I am not so tech-y about the working of GPS/indoor GPS, but I am interested more in this technology specific to indoor GPS (repeaters).

    Can the smartphones get indoor GPS signals correctly and quickly? If the smart phones are really smart that they can connect to GPS satellite from indoor locations, then do the GPS repeater products become obsolete?

    — Saad B.

    Author Frank van Diggelen replies:
    The simple answer to your first question is yes, many of these smartphones can get GPS signals indoors. But indoors is a big and varied place, and the more complete answer is that the term “indoor GPS,” like “offroad vehicle,” describes the presence of a capability, not the absence of all limitations. So even if your GPS receiver works indoors in some locations, there will always be other places it doesn’t. And it will generally work better where there are stronger signals, like outdoors.

    Similarly, for your second question, high-sensitivity GPS will work some places indoors, but not everywhere, so there is a role for repeaters. However, GPS repeaters are like a long cable from the repeater’s receiving GPS antenna; so any GPS receiver that gets signals from a repeater will compute the position of the repeater’s receiving GPS antenna.

    Nice article. One comment and one question.

    Comment: The IGS ultra-rapids that started in 1999–2000 were from the beginning available for the future. They always contained 24 hours of estimated orbits and 24 hours of predicted orbits usable in real time. As I was responsible for generating these products within the IGS at that time, I am pretty sure that was the case.

    Question: I do not understand why you write that turning off SA (Seletive Availability) was an enabler for A-GPS!? I know that one possible feature of SA was an artificial degradation of the satellite ephemerides but this option was never exercised to my knowledge. So using a global network to obtain broadcast ephemerides and predict them into the future was always possible. Nothing fundamentally changed when SA was turned off!?

    — Tim Springer

    Frank van Diggelen replies:
    Just to be clear, the article enumerated seven enabling technologies for the revolution of GPS in cell phones (they are: A-GPS; massive parallel correlation; high sensitivity; coarse-time navigation; low-power TOW decoding; host-based GPS; and RF-CMOS), and a dominant spin-off technology: long-term orbits good for many days into the future.
    The demise of SA made it easier to predict long-term orbits for two reasons: technical and commercial.

    Technically, if you used the code- or carrier-phase measurements in your orbit modeling, then it was easier if these measurements were not degraded. Of course, you could have corrected them differentially, but the article makes the point that things were harder (not impossible) when SA was on.

    On the other hand, if all you did was use the broadcast ephemeris in your predictions, then as you suggest nothing changed, technically, if the ephemeris degradation option was not exercised. But the fact that this degradation option existed made it a more difficult commercial proposition to develop a system for predicting many days of ephemeris. Thus the end of SA certainly helped facilitate the commercial availability of predicted ephemeris that is valid for many days into the future.

  • Directions 2010: It’s the Economy, Stupid

    At the end of every year, I devote this column to Directions 2010 in which I discuss significant developments, trends, technologies, and companies in the GNSS industry.

    Two years ago, I wrote about the Year of the Who. Not GNSS technology; rather, the people and companies they run.

    Last year, I highlighted 2009 as being the Year of the Other GNSS. The little brother of GPS…GLONASS.

    I’ve thought a lot about this year’s column. Some have said that next year will be the Golden Year for GNSS with the launch of the first Block IIF satellite, possibly the launch of the first GLONASS-K satellite (broadcasting CDMA), launch of Japan’s first QZSS satellite, launch of a GAGAN geostationary satellite, yada, yada, yada.

    The problem with this, as I see it, is that these developments will have very little impact on GNSS users in 2010. All of them have been on the drawing board for years, all have been vetted, and most of them are behind schedule. In a nutshell, it’s beating a dead horse. How many times can one talk about Galileo? Even I get tired of writing about the next satellite launch, the next signal to be broadcast, the next GNSS to be developed, etc.

    From a GNSS technology perspective, do you know what excites me? Optimizing the current constellation of satellites that are already in orbit. That’s where the “rubber hits the road.” With a few tweaks of the GPS constellation, our “brownout” periods would largely disappear immediately. No waiting for new satellite launches, no waiting for new GPS receiver technology to purchase. Just like when Selective Availability (SA) was turned off…boom…an overnight difference. Of course, I know it’s not quite as easy as turning off SA, but I think you see my point.

    However, even though it’s likely that the Air Force will reconfigure the GPS constellation to reduce the GPS brownouts in 2010, that’s not the focus of this column (although it’s a close second).

    Nope. The statement that best defines the GNSS industry for 2010 is one I’ll borrow from Bill Clinton that he used during his campaign for the U.S. presidency in 1992…

    ”It’s the economy, stupid.”

    Why? The current economy is beating the tar out of the GNSS industry.

    Revenue for high-precision GPS/GNSS systems is down significantly. Revenues from Trimble’s Engineering & Construction division were down 22 percent in the third quarter compared to the same period last year. Revenues for Hemisphere GPS, a GPS manufacturer focused on the agriculture industry, were down 31 percent in the third quarter compared to the same period last year.

    When revenue decreases significantly, companies typically react by cutting costs. Some of the first expenses cut are research projects that can lead to revolutionary developments. Companies also review personnel requirements and subsequently reduce headcount.

    Decrease in corporate revenues also trickles down to the distribution channel. The GNSS distribution channel (surveying equipment dealers) have taken a big hit. Layoffs are prevalent and many dealers are reduced to operating with “skeleton crews.”

    In the service sector, I’ve heard from several companies that bid pricing on construction projects is coming in at 20 to 30 percent less than the pre-recession period and bid competition for each project has increased. This results in a lower profit margin for the successful bidder and, as a result, there is less money available in capital equipment budgets for contractors.

    On the flip side, the market for used surveying equipment is hot, GPS/GNSS equipment included. Companies and individuals looking to trade equipment for cash or going out of business altogether are pushing their equipment to the market, primarily using eBay. This flood of “fire-sale” surveying equipment contributes somewhat to the declining revenue for new GPS/GNSS equipment.

    It’s a vicious cycle that’s difficult to recover from.

    In 2005, economics Professor’s Hugh Patrick and David Weinstein from Columbia University and economics Professor Takatoshi Ito from the University of Tokyo wrote about “…a prolonged period of stagnation and malaise…Subpar growth, failing banks, plummeting real estate and stock prices, deflation, unprecedented unemployment, and huge government liabilities have persisted, despite extraordinary fiscal and monetary policy fixes.”

    It reads as though they were writing about today’s U.S. economy, but they were actually writing about the Japanese economy which has been stagnant since 1991. Their book is titled “Reviving Japan’s Economy.”

    It’s a little disconcerting to think about the U.S. recession lasting that long, but I do have a hard time seeing the light at the end of the tunnel. I think real estate prices will continue to depreciate and the effects of the commercial real estate market will reverberate through the economy for several years.

    Let’s face it: high-precision GNSS receivers are a luxury item for the most part. In some cases, the argument can be made that the investment has a ROI (Return on Investment) that justifies the capital expenditure. But in many instances, companies and individuals might decide to save the cash and forego the efficiency that GNSS equipment offers or continue using their legacy GPS equipment that may not be the most efficient technology, but it does the job.

    That, my friends, is the reason that the economy, and not a GNSS technology development or trend, will be the most significant factor in the GNSS industry in 2010.

     

    From the Mailbox

    We received a Letter to the Editor regarding my last column titled “As Loran Fades, Attention Shifts to DGPS and SBAS.” Following is the letter:

    As I read the title of this month’s Survey newsletter column, “As Loran Fades, Attention Shifts to DGPS and SBAS,” it came to my mind that there are many people around the world who do not recognize the difference between a position, navigation, and time (PNT) system and an augmentation of a PNT system — a difference that was not clearly pointed out.  I have heard many PNT users expound on how good an augmentation is and, to my amazement, how the augmentation could provide service despite a GNSS outage. I’ve stopped being surprised. After all, I still remember the days when Galileo was being touted as a backup to GPS.

    Unfortunately, the leadership worldwide has become decidingly less technical over the last decade, and without proper explanation from staffers (who have also become decidingly less technical), the point is lost.

    The simple fact is that augmentations are of little or no use if the system they augment is unavailable. Perhaps this point should be made, and made loudly and strongly — particularly in the case of the scheduled termination of Loran. The same holds for the respective differences between real-time navigation, long-term positioning, and time and frequency — distinctions, again, that are lost to many. While WAAS, NDGPS, and even HA-NDGPS are admirable efforts that highlight what a group of talented, dedicated engineers can do, maybe what we need is a PNT 101 course/flash card set for those “technically challenged” so they can better understand the ramifications of their decisions. It took me and millions of others five years to get a bachelor’s of engineering degree; we cannot expect the leadership to learn engineering overnight.

    I remember fondly the times when, as a junior engineer, I had five layers of management above me that all held engineering degrees. Today I ca
    n’t go up to any level and find a single one. What went wrong?  I do not know, but I do not think it bodes well for the world.

    In any event, best regards to GPS World, and Happy Holidays

    — a wistful engineer

     

    Thanks for the note.

    I believe there are some very smart people in the federal government running these programs. Sadly, I think the demise of programs like Loran are largely the result of political efforts, or lack thereof, rather than a lack of technical understanding. If no one is going to fight for the program, most likely it’s not going to be funded. Furthermore, I think most people agree, engineering educated or not, that GPS is a venerable system. However, it’s debatable whether Loran is a suitable back-up or not.

    Perhaps the title of my article was a bit misleading, too. I don’t think anyone would claim that GPS augmentation is a back-up for GPS. My point was that resources (energy and money) and focus would shift to GPS augmentation as it has become the replacement for Loran in the marine and aviation industries.

    — Eric

  • Interservice/Industry Training, Simulation & Education Conference

    By Art Kalinski, GISP

    The I/ITSEC (Interservice / Industry Training, Simulation & Education Conference) held in Orlando is not a GIS conference but GIS is playing an increasing role in training and simulation. With over 5,000 attendees and over 500 exhibitors this is the conference of the year for those in the training and simulation business. This is a large conference that can’t be taken in by one person so the following are some snap shots taken from a GIS perspective.

    I/ITSEC demonstrated that the bar is being raised in all aspects of this multi-million dollar technology industry. The early days of training simulation was exemplified by LINK trainers which were early aircraft trainers that trained thousands of pilots during WWII. The trainers were estimated to have saved thousands of lives and millions of dollars in aircraft. Now the current generations of trainers have moved well beyond the simple stick, pedals and crude instruments that were the hallmark of the early LINK trainers but the objective is still the same. Substitute training simulators for real hardware and save lives and millions of dollars in the process.

    IITSECThe aircraft trainers demonstrated at I/ITSEC are as specialized and sophisticated as the aircraft they simulate. The simulators are no longer gee whiz video games. The current trainers approach realism that in some cases is indistinguishable from reality. Some simulators that were on display even simulate G forces through tactile sensations created by the seats. I tried one out and the affect was compelling but still not the real thing. If you are a video-gaming enthusiast this conference is a “Candy Store.” The hardware is absolutely real and most of the simulators use very high powered computer environments.

    GIS plays an increasing role as engineers seek to create training simulators that are not only used for generic training but actual mission rehearsal. The simulators need to accurately display features, terrain, navigation and communication while also displaying different weather conditions. One can see the blurring of the line between being in an actual aircraft, being in a trainer or remotely piloting a UAV.

    In the training simulation business they use the term “database” slightly differently that we do in GIS. Their database includes all the GIS type vector data of the flight environment but also includes, ground elevation models, draped imagery, 3D structure models, the objects and skins that populate the models and all the underlying physics that make the models behave realistically.

    Fast accurate 3D model creation is major requirement of our military for training but increasingly more important for mission rehearsal. 3D modeling is becoming more sophisticated and robust with four vendors PLW, IAVO, Cogent3D and Clear Edge 3D approaching the “Holy Grail” of modeling, an automated process to create 3D models from ortho, oblique and ground level images with minimal human intervention.

    I saw improvements in display technology, nothing really new but significant refinements. Large HD flat screens have replaced smaller LCD monitors. More air and ground simulators now use spherical and wrap around projection screens. There are also significant improvements to the imagery as they refine the optics to take full advantage of the screens and reduce distortion. JVC and Sony both displayed extremely high resolution and very high refresh rate digital projectors that showed no signs of blurring on even fast moving objects. They made me want to scrap my Blu-ray / 1080p home theater until I saw the price tag. Yes, if you have to ask you probably can’t afford it. With the new displays they can accurately show fast moving aircraft from an initial pinpoint on the horizon to a Mach 3 fly by.

    The blurring of the lines between the gaming industry, simulation and GIS continued on the ground with numerous ground combat simulators. Avatars are becoming so realistic in motion and detail that they rival video of actual players. Avatars not only move with fluid motion but their movements have built in physics so they behave appropriately when running and jumping with back packs and other loading conditions. Many of the ground simulators work with real geo-referenced data and actual building imagery. Even more impressive are recognizable emotions on the Avatar faces.

    One group of tools that has been used to create realistic avatars is motion tracking devices. Even here the bar has been raised. Last year one company demonstrated the ability to make an Avatar move in perfect synchronization to movements of a live actor wearing a suite with sensors that were tracked by computer. This year two companies were displaying the same capability and both were upstaged by a new company, Organic Motion, that did the same avatar mimicking but without wearable sensors. They instead used multiple video cameras and computers to analyze the motion of objects in 3D space and then immediately mimic the motion with avatars.

    Organic motion.
    Organic motion.

    A Canon distributor was demonstrating a Canon mixed media set of 3D goggles. This is a significant refinement of an experimental display I saw several years ago at a GIS conference. Those goggles displayed GIS or CAD drawing data overlaid on the real world view. The hard part was maintaining registration of the abstract data with the real world despite head movements. The early version did that by placing a GPS receiver on the head piece to constantly serve as a geo-reference. It was crude but I could imagine that some day construction workers would wear these kinds of goggles to “see” buried cables and piping prior to digging. Obviously GIS data accuracy, integrity and verification would be paramount.

    The new Canon mixed media goggles were a significant leap in quality. The resolution and optics were superb. When I put them on I could still see the real world but overlaid in my field of vision were 3D objects that looked like they were actually their. I’m not sure where this will lead but the viewing of GIS data on the real world is certainly now possible.

    Canon Mixed Media.
    Canon Mixed Media.

    Professor Amela Sadagic and Marine Corps Captain Aaron Burciaga of the Naval Postgraduate School were demonstrating a Virtual Sand Table that combines projected imagery and computer notations onto a table with 3D physical models.

    Virtual Sand Table.
    Virtual Sand Table.
    Sand Table 2
    Sand Table.

    The trainers are not only visually impressive but are providing very realistic tactile feedback. Some are as simple as a video firing range that not only provided a realistic video image but provided a realistic kick back by using a CO2 cartridge within the fake magazine. I tried the Glock 19 and it felt exactly like firing my own gun on a range but without the ammo cost and a more realistic target environment. Even Segways have entered the training and simulation business with Marathon Robotics demonstrating human sized mannequins that can move about a training environment through wireless control. The robots even have on-board intelligence to react to unexpected situations.

    Marathon Robotics.
    Marathon Robotics.

    A very gratifying volunteer event in the Exhibit hall was Lockheed Martin’s purchase of cases of personal items needed by our troops in-theater. They set up a “Fill the Box” production line staffed by conference attendees who moved down the line filling a box that was finished with a personal note to a service member. The boxes were sealed and shipped by Lockheed Martin whose motto is “We never forget who we’re working for” and in my personal experience they really mean it. This was a good close to a very interesting conference.

    Lockheed Martin.
    Lockheed Martin.

  • Letters

    Below is a letter sent on November 3 by Senators Joe Liberman, chairman, and Susan M. Collins, ranking member, Committee on Homeland Security and Governmental Affairs, to Secretary of Homeland Security Janet Ann Napolitano protesting the termination of the Loran service:

  • Out in Front: From IAIN to 101

     

    This is one of those mind puzzles that challenge you to transform one word to another in as few moves as possible.

    No, it’s not. But it does constitute a journey of sorts. I made it in a few minutes, while listening to David Last give the keynote address at the 13th World Congress of the International Association of Institutes of Navigation.

    Departure point: ballroom of the Clarion Hotel, Stockholm, Sweden, late October. Destination: GPS 101, an online webinar for engineers from PNT-related (as in, kissin’ cousins) disciplines, sometime in the near future.

    Last described the United Kingdom’s Royal Institute of Navigation (RIN), of which he is president, as “a failing business in a booming industry.” He added that many institutes of navigation struggle with falling membership and declining revenues, if not outright losses. Contrast this with huge satnav growth, and the exploding numbers of  “products that are more powerful, more user-friendly, more cost-effective, every time we have met.” Rising industry, falling professional associations.

    My concern here is not the well-being of institutes, but the global technical awareness possessed by engineers and designers from a range of industries whose products now seek to incorporate position, navigation, and/or timing. Phones, cameras, cars, binoculars, road tolling, parole anklets, and so on.

    This magazine reaches and educates those far-flung technical personnel, in addition to our readers already working in and supplying the surveying, aviation, military, marine, mapping, precision agriculture, and other more traditional positioning fields. I think we do so very successfully.

    But I was surprised by the low level of awareness evidenced by participants in July’s webinar, “The GPS Constellation and More,” with Colonel David Madden, GPS Wing Commander. Presumably attendees came from among our readers and web visitors, but some of their questions were beyond (or below) elementary. Editor Don Jewell, who moderated that webinar, saw the need for a GPS 101 course, and I fully agree.

    We don’t intend to compete with companies or institutes offering technical tutorials. Rather, to offer a stepping stone up to those tutorials, and to leverage our free and extensive global reach to engineers everywhere.

    Returning to the RIN president for Last words, “What was once a specialized set of professional techniques has expanded into an industry with hundreds of millions of users. Navigation is a unique place where bright engineers — hardware and software — work alongside systems analysts, geographers, surveyors, geodesists, mapmakers, and those who design, manufacture, market, and support navigation equipment, and those who use their products as practitioners. These people are today’s navigators.”

  • Expert Advice: Availability Gaps: Solutions for Aviation

    Directions 2010

    James L. Farrell
    James L. Farrell

    By James L. Farrell

    Recent attention given to aging GPS satellites and availability gaps from lagging constellation replenishment have provoked deep concern, particularly within the aviation community. Available remedies include exploitation of well known but unused methods plus new techniques; those discussed here have future relevance, with or without availability gaps.

    Even with far greater coverage from multiple GNSS, crises could emerge from severely stronger interference levels or other unforeseen events. Advance preparation for any such occurrence would avoid the waste, confusion, and blind alleys that generally arise with the sudden appearance of an emergency.

    GPS lives up to expectations, brilliantly performing as advertised. Even that best-ever performance must and does have tolerance for occasional error; examples, though rare, are well documented. To live with less than perfect performance, the industry relies on integrity testing: comparison checks using extra satellites to detect inconsistencies and exclude questionable data.

    Nevertheless, it is universally recognized that GNSS, even with existing fault detection and isolation or exclusion (FDI/FDE), is still not perfect. The ramifications of growing dependence on GPS have thus attracted more attention. The overall subject can be subdivided into general areas involving the likelihood of:

    • reduced availability and
    • reduced dependability (integrity, its verification, plus backup).

    Although I mainly address the first topic here, the second unavoidably intertwines itself, making it difficult to keep them separate. Despite wide acclaim for the excellent 2001 Volpe Report, commitment to a key means of backup for GPS remains unclear at this time. Possibility of a shortfall calls for a review of both existing methods and procedures, and possible means for closing the gap.

    Current Methods

    Today’s air traffic management  designs demand constant replenishment of instantaneous position by full fixes.

    Full Fix 1 RAIM. When each data vector must be a self-sufficient source of instantaneous position, a requirement arises for enough satellite sightline directions with geometric spread at all times. That interdependence is magnified when more satellites are added to provide FDI/FDE, requiring every subset of four within the enlarged group to support the requisite geometry. With this all-or-nothing posture, data lapses form a major stumbling block. A data gap that is only partial equates to a loss of GPS.

    Position-Oriented Approach. Especially at high speeds, as in flight, instantaneous position is highly perishable. With little or no emphasis placed on accurate dynamics (beginning with velocity), demand for continuously accurate instantaneous position is highly dependent on abundant data. That abundance includes sufficiently high data rates, since latency becomes a significant liability without usage of a dynamic file.

    Carrier Phase (Classical). Successful use of carrier-phase information is decades old. Although ambiguity resolution is not required in all carrier-phase applications, requirements for cycle-slip detection are quite common. More common yet — in fact, virtually ubiquitous — is the need to maintain phase continuity via a carrier-track loop. When those needs are satisfied, sub-wavelength instantaneous position is obtainable. Challenges involved, however, have produced among users a wide variation in perception of value. Some negative perceptions have arisen due to cutting corners in formation of carrier phase, or merely settling for delta range, by some receivers. Further, a cycle slip, even if only rarely overlooked, can be catastrophic in some operations.

    Imperfect Validation. As already noted, verification is not my main topic here, but the issue is inescapable. Shortcomings include hard evidence of certification improperly bestowed, and severe limitations of go/no-go criteria (as with an automobile’s dashboard warning lights, we can learn if a performance trait is unsatisfactory — but a trivial excess produces the same indication as an imminent danger).

    Necessary Changes

    Extremely powerful and versatile means to improve performance have been available for a very long time. Kalman’s original paper, half a century ago, formalized an optimal way to achieve such performance. While Kalman estimation is commonly used today, its effective reach is almost invariably limited to data resident within each proprietary box of equipment.

    The resources for providing centrally processed solutions for data from every source of information available, any combination of sources, any subset that may exclude any sensor or group, or any individual source in a federated configuration, are well known. Every conceivable choice from among these solutions can be made concurrently available; note the inherent backup.

    However, all this capability is forsaken or lost by continued use of:

    • interfaces chosen poorly or from outdated standards;
    • undue consolidation within isolated equipment packaging;
    • overextended proprietary rights; and
    • limited, demonstrably flawed validation methods.

    Drop Demands for Full Fix. An immediate explosion of benefits can follow from acceptance of partial information. Countless examples could be cited, but two obvious ones suffice:

    • Within GPS or GNSS, not all space vehicles (SVs) would be simultaneously affected by scintillation; ionospheric disturbance effects vary with both location and time. A similar case holds for multipath. Data from some SVs could be rejected, by decisions made external to a receiver, without forcing rejection of all.
    • Central processing — not within any one equipment box — has always offered potential for other sources (distance-measuring equipment or DME, and so on) to make up for incomplete sets of SV data.

    My broad goal here is to take advantage of information not currently used and to prescribe corrective strategies. That objective has not been widely pursued due to perceived lack of urgency. GPS availability has thus far been more than satisfactory to a multitude of users — but that could change.

    Availability Enhancements. For about two decades, the industry was effectively guided by a strong preference for the trait whereby every data refresh event was self-sufficient. A major reason for this was protection against gradual veering: a snapshot sequence is less sensitive than a continuously evolving path estimate. The cost, of course, is forfeit of benefits conferred by the sequence’s history. More recently, a middle ground was sought to mitigate the resulting loss; subfilters used as much new data as possible while making some use of knowledge from an estimator’s covariance matrix.

    I promptly endorsed that approach and sought to carry it to the limit. A single-measurement receiver-autnomous integrity monitoring (RAIM) resulted, offering an independent integrity test for each separate observation. Despite its rigorous derivation, the technique is quite simple in practice. Further, it bridges a gap that formerly separated integrity test from optimal estimation, while also having significant advantages over conventional RAIM:

    • separation translates to independence from other satellites, and therefore from geometry (effective DOP of unity)
    • ability to use different error variances for different observations (for example, with nonuniformity in signal strength and/or elevation).

    With this discussion, we have clearly left the realm of well-known subjects with self-evident prescriptions. Much of what follows likewise falls into the category of relatively obscure methods.

    Beyond Position-Oriented. A time history
    of GNSS observations, with or without an inertial measurement unit (IMU), inherently carries dynamic information. A file with observational history from multiple sources of course enables the aforementioned explosion of benefits. The obvious immediate offerings include:

    • closing of data lapses via information sharing;
    • intrinsic backup with automatic activation;
    • vast reduction of latency effects (for example, from 200 meters to less than 1 meter at 400 knots after 1 second, with easily obtainable velocity accuracy below 1 meter/second);
    • formation of 1-sigma projected future error (within reason).

    Beyond these lie, once again, some lesser known techniques, including a few that are virtually nonexistent in operation at the time of this writing. With GNSS, the full potential of dynamics calls for a revisit of carrier phase.

    Carrier-Phase Developments. Rather than pursuit of unnecessary sub-wavelength fixes for aircraft (for example, with 20-meter wing span moving at 400 knots), the true value of carrier phase in flight lies in enhanced dependability.  Sequential changes in carrier phase over 1 second provide excellent dynamics information, with or without an IMU.

    Recognition of this opportunity led to the concept of segmentation, whereby position is determined separately from dynamics. Carrier-phase sequential changes with ambiguities unresolved can provide precise (1-centimeter/second RMS with IMU; decimeter/second without) streaming velocity independent of position. Dead reckoning then provides a priori position correctible by pseudoranges.

    One advantage of this scheme is subtle: with 1-second phase change propagation effects generally at 1 centimeter or less, no mask is needed. The geometry benefit is obvious, and flight experience has verified it. This raises another segmentation characteristic: the single-measurement integrity testing is applicable to each carrier-phase sequential change and to each pseudorange, separately and independently.

    These capabilities are untapped in essentially all operational systems — air, land, and sea — and all stand to gain. Yet another opportunity can be added: ability to sustain operation even if every SV has repetitive data gaps. This advantage is best exploited with receivers described next.

    FFT-Based Processing. Correlators and track loops in GNSS receivers can be replaced. The theory is age-old: multiplication in the frequency domain corresponds to convolution in time (and vice-versa). Thus a term-by-term product of a digitized receiver input’s fast Fourier transform (FFT) with the reference pattern’s FFT can, after an inverse FFT, provide outputs equivalent to full sets of correlator responses. Today’s processing and analog-to-digital converter capabilities offer feasibility.

    In addition to reduced vulnerability to jamming (not covered here), advantages include:

    • access to all cells (not only a track loop’s subset)
    • guaranteed access (stability is not conditional)
    • linear phase-versus-frequency; no phase distortion.

    Features from the preceding section, combined with these traits, offer extreme robustness.

    Extension to Surveillance. The practice of transmitting responses to RF interrogations has, for many decades, been quite vulnerable to overload (garble; one user’s information is everyone else’s interference). One report described the unsurprisingly poor performance during the first Gulf War, and identified a remedy: squitters with separate assigned time slots, spontaneously firing the transponder transmitter without interrogation. Immediately, a sea change in capability offers every participant an opportunity to track every other participant. With no interrogations, garble would disappear.

    This dramatic increase in capacity has been successfully demonstrated with the use of an existing communication link and existing airborne equipment: GPS receivers and Mode S squitters. Subsequently I enthusiastically advocated adoption of the technique with one fundamental modification: replace the data bits of the transmitted messages with measurements instead of coordinates.
    Additional improvements include small shifts in time (reducing bits needed for time tags) and recomputation of measurements that would have occurred at the center of gravity (to mitigate rotation effects). Collectively, the full set of procedures offers a vast and compelling list of benefits.

    Conclusions

    Capability and dependability of navigation and surveillance can be enormously increased. The key lies not in new inventions nor provisions, but in use of newer methods, (among them, FFT-based receivers, segmented estimation, and 1-second carrier-phase changes) while abandoning habits such as:

    • dismissal of partial fix data
    • preoccupation with full fixes for instantaneous position irrespective of dynamics
    • preference for location pseudomeasurements rather than the measurements themselves
    • reliance on proprietary software in equipment boxes
    • RF interrogation/response sequences instead of squitters.

    The industry can either adopt changes or continue to settle for performance levels at a minor fraction of the intrinsic capabilities available from our present and future systems.

    James L. Farrell worked for 31 years at Westinghouse in design, simulation, and validation of navigation and tracking programs. He continues teaching and consulting for private industry, the Department of Defense, and university research through Vigil, Inc

  • As Loran Fades, Attention Shifts to DGPS and SBAS

    Few precise-positioning users have employed Loran in a professional sense, although maybe you have in your personal life if you’re a airplane pilot or a mariner. Then again, if you’ve flown as an airline passenger or cruised onboard a ship, you’ve benefited from the back-up to GPS that Loran provides. Similarly, if you’ve used a mobile phone recently; you don’t see it, but the wireless carriers all use Loran as a back-up. That back-up is about to go away.

    Loran was developed initially for marine navigation and then adopted for aviation navigation. I used Loran-C for aviation navigation in the early 90’s after I earned my private pilot’s license. It was much easier than triangulating off of VORs and NDBs. Yes, GPS receivers for aviation were starting to emerge at that time but flying is expensive so a hand-held GPS was an out-of-reach luxury for a newlywed who just bought his first house and was preparing to start a family.

    Loran is a terrestrial (ground-based) system of broadcasting towers, somewhat synonymous with NDGPS. You can read details about the system in the link I provided, but essentially it’s a line-of-sight system in which the Loran receiver antenna needs a direct path to the tower to utilize the signal. Coverage depends on the density of the broadcasting towers. Some regions are covered better than others and when I was using it, there were many areas that were not covered. Accuracy is always an ambiguous subject with respect to navigation technologies, so I’ll go out on a limb and say that Loran-C accuracy is repeatable to about 20 meters. A proposal was floated to upgrade Loran to a system called e-Loran which is reportedly accurate to about 9 meters.

    Anyway, over the past several years there’s been a discussion about what to do with the Loran system because it’s clear that GPS has supplanted Loran as the primary navigation system for marine and aviation. Several articles have been published in GPS World by industry experts with most being in favor of maintaining Loran. The primary argument is that we need a back-up system for GPS, not only for navigation, but for the many invisible ways that GPS supports the national infrastructure (financial networks, wireless communications, transportation).

    Here are several relevant articles, from most recent to further back:

    New Backward-Compatible Technique to Develop GPS+eLORAN User Base

    Coast Guard Jettisons Loran

    LORAN: What the President Meant to Say Was…

    Loran Study Finally Unleashed: Says Keep It, Best Option

    eLoran, Superhero Sidekick

    Loran Gets a Witness

    The Case for eLoran

    In addition to these articles , the U.S. government publishes the Federal Radionavigation Plan (FRP) roughly on a biennial basis. There was one published in 2001, then 2005 and the last one was published in 2008/early 2009. It is the official policy document in which all US navigation systems are planned. According to the FRP, it is prepared jointly by the Department of Defense, Department of Homeland Security, the Department of Transportation and a number of other contributing government agencies.

    If you don’t have time to read the 2008 FRP, following is a telling statement from the document:

    “In March 2007, the DOT Pos/Nav Executive Committee and the DHS Geospatial/PNT Executive Committee accepted the findings of the Institute for Defense Analysis’ Independent Assessment Team and approved to pursue the designation of Enhanced-Loran, commonly referred as eLoran, as a national PNT backup for the U.S. homeland.

    At its March 2007 meeting, the National Space-based PNT ExComm supported this approach and tasked DOT and DHS to complete an action plan that includes identifying an executive agent, developing a transition plan to address funding and operations and requesting the approval by the DOT and DHS Secretaries resulting in a final decision. DoD has not approved eLoran as a GPS backup for military applications.

    In March 2008, the National Space-based PNT ExComm endorsed the DOT/DHS decision to transition the LORAN system to eLoran.

    With respect to transportation to include aviation, commercial maritime, rail, and highway, the DOT has determined that sufficient alternative navigation aids currently exist in the event of a loss of GPS-based services, and therefore Loran currently is not needed as a back-up navigation aid for transportation safety-of-life users. However, many transportation safety-of-life applications depend on commercial communication systems and DOT recognizes the importance of the Loran system as a backup to GPS for critical infrastructure applications requiring precise time and frequency.

    Currently, DHS is determining whether alternative backups or contingency plans exist across the critical infrastructure and key resource sectors identified in the National Infrastructure Protection Plan in the event of a loss of GPS-based services. An initial survey of the Federal critical infrastructure partners indicates wide variance in backup system requirements. Therefore, DHS is working with Federal partners to clarify the operational requirements.”

    By the way, that Independent Assessment Team mentioned in the first paragraph was led by Brad Parkinson, who knows someting about GPS. Further, the government read the report behind closed doors but refused to release it, until forced to do so nearly two years later, by public information access filings.

    There still aren’t any answers to the question about a real back-up to GPS. No doubt it’s a vulnerable system. But that’s a subject for another day.

    What’s Loran got to do with us?

    The reason I’m writing about this is because as support for Loran wanes, attention (resources and focus) shifts away from Loran, it comes to bear more intensely on GPS navigation and its augmentations for marine and aviation; specifically DGPS and SBAS (WAAS/EGNOS/MSAS).

    With a significant policy shift such as this (albeit it has been in the cards), manufacturers stop allocating engineering development resources to the products/technologies with a dim future and shift those resources to products/technologies with a bright future. True, DGPS has been around for better than a decade and SBAS for about half that time so there’s been plenty of time for manufacturer’s to exploit those technologies, but there is still a lot that can be done.

    Engineers are experimenting with and implementing technologies in some interesting areas.

    HA-NDGPS. High accuracy NDGPS. Currently with a high performance DGPS receive
    r, one can attain about meter-level accuracy. Testing with HA-NDGPS, using a dual frequency GPS receiver shows that accuracies in the 10cm (95%) horizontal and 20cm (95%) vertical range are achievable within a 100 mile baseline according to the US DOT Federal Highway Administration Turner-Fairbank Research Center. Test broadcasts are being sent from a site in Hagerstown, MD.

    Broadcasting DGPS/SBAS corrections via NTRIP. The emergence of RTK Networks has spurred the popularity of using the internet to deliver GPS corrections. NTRIP has become a commonly used method of accomplishing this. One of the weak points of DGPS technology has been the reliability and expense of broadcasting DGPS corrections via the 283-325kHz band. Of course, with NTRIP one must have internet access somehow and that typically happens via WiFi or GSM/CDMA mobile phone network. But it’s not that complicated. I’ve been with a GPS user who has pulled the SIM card from their iPhone, plugged it into a GPS receiver, and begin receiving DGPS corrections immediately.

    During my last webinar, someone had posed the question if receiving SBAS corrections is possible via the internet in order to bypass the requirement to maintain visibility of the SBAS geostationary satellite. Streaming SBAS corrections via the internet is already happening in Europe. Users can access EGNOS corrections and bypass the EGNOS geostationary satellites by using SISNeT. A similar type of system could be implemented for any SBAS and not necessarily by the SBAS service provider. It could be a commercial entity.

    I think the internet and GSM/CDMA mobile phone networks are really going to transform the way we transport data from reference stations to our receivers in the field. We’ve been fighting this battle of delivering GPS corrections for better than a decade. In the past, we’ve experimented with FM pagers and landline modems and now we’ve settled on low frequency radiobeacon, VHF/UHF/Spread spectrum and geostationary satellites but none are close to the perfect solution. GSM/CDMA mobile phone networks may be the final solution as the networks continue to build-out towards complete geographic coverage. Of course, we are helped immensely by the mobile phone industry whose focus on data for the many new social networking applications will drive the price of data plans downward.

    By the way, almost all wireless carriers use Loran as a back-up technology; highly precise timing is a key aspect of how wireless communication works. The carriers use GPS for that, but if GPS goes down — as it did in San Diego during a memorable jamming episode a few years ago — so do all cell phones, if the carriers don’t have a timing back-up. In San Diego, they didn’t. Just something to think about, if you are using your mobile phone network to transport data or receive corrections.

  • A Little Q&A Follow-up and Feedback on My Last Column

    I received some feedback on my last column entitled “What’s the Difference Between a Used Car Salesman and a GPS Salesman?” Most of the comments were positive in that the technical content was reasonably deep and thorough. However, I did receive a couple of e-mails from folks who were offended by the comparison.

    The joke has been around for a long time. As I mentioned, I recall hearing it in the early ’90s. I believe it was while I was at a conference somewhere in British Columbia, Canada. Anyway, I used to be a GPS salesman of sorts and I never took offense to it. I figured if I was doing my job correctly, there was nothing to be offended by. But, the fact is the joke has maintained staying power because a number of people do exist who fit that description. Fortunately, they don’t seem to hang around very long in the industry. On the flip side, over the years I’ve met many competent GPS sales professionals that have earned my trust. Many of whom I consider my friends.

    Leftover Webinar Q&A

    There are some lingering questions left over from the last webinar (September). There are still a few questions left after this that I’ll post in future newsletters.

    Question #1: If GLONASS has a full constellation by 2020, would it be fair to say a L1, L2, and GLONASS receiver would be fine because you would really only have a L1 and     GLONASS receiver thus therefore enough sats?

    Gakstatter: The question is referring to the semicodeless sunset I’ve written about in the past. You can read about it here.

    Back to the question. Generally speaking, I would say yes but it’s going to depend on the receiver firmware design. If the receiver is optimized to depend on L2, then the firmware would have to be altered. Then, the question is whether the manufacturer is willing to update the firmware.

    Question #2: If SBAS is made for aviation safety purposes, why it does not cover all of the world? Will the coverage expand in the future?

    Gakstatter: Building an SBAS is very expensive and time-consuming project. If I recall correctly, the US WAAS total expenditure to date is well into several billion dollars. The FY2010 annual budget for WAAS is just under US$100M.

    The nature of SBAS is that they are regional systems. Currently, there are three. WAAS covers most of North America. EGNOS covers most of Western Europe and North Africa. MSAS covers the region around Japan. GAGAN is still in the planning stage and will cover India and surrounding areas.

    This still leaves South America, Australia, and Africa as major land masses not covered by SBAS.

    MSAS has the potential to cover Australia and EGNOS has the potential to cover Africa. Whether that happens or not is more political and financial than technical issues.

    Also, once GPS L5 is broadcast by a full constellation, the requirement for SBAS for aviation will diminish because GPS in aviation will transition to dual frequency (L1/L5) thus mitigating the effects of the ionosphere.  However, there would still be a question about position integrity, which is a central function of SBAS. The debate within some countries that do not currently have SBAS coverage is whether to invest in a SBAS or hold out for GPS L5. However, a full satellite constellation broadcasting GPS L5 will not be operational until ~15 years from now.

    Question #3: Can we obtain SBAS in other regions in the future?

    Gakstatter: India is far along with their GAGAN SBAS. At one point, a test signal was being broadcast. Within the next few months, India reportedly will be launching a geostationary satellite for GAGAN.

    Russia is reportedly in the early stages of developing their SBAS called SDCM (System of Differential Correction and Monitoring).

    The interoperability among SBAS is virtually seamless. A GPS receiver utilizing WAAS in North America is able to use EGNOS in Europe and MSAS in the Japanese region. Most receivers will automatically tune to the local SBAS given the SBAS satellites in view. However, some must be manually set to “look” for the SBAS satellite(s) of that region.

    Question #4: GNSS improves the productivity. What about the precision? Are there any reports testing/comparing GPS vs GNSS?

    Gakstatter: At this point, the ideal situation would be to only utilize GPS satellites. The quality, integrity and monitoring is world-class. Unfortunately, for RTK users there just aren’t enough of them in orbit to be able to work consistently throughout the day.

    The quality and reliability of GLONASS measurements aren’t as good as GPS yet. The ephemeris data and clock corrections are worse and there isn’t world-wide monitoring of the satellites. Russia’s program managers have stated they are striving to reach the same measurement quality as GPS.

    So, the short answer is no, I wouldn’t expect GPS/GLONASS to improve positioning precision. However, it also depends on the scenario. If the comparison is between a GPS constellation of 5 satellites with a PDOP of 5 against a GPS/GLONASS constellation of 5 + 5 with a PDOP of 2, then I’d vote for the latter.

    There is an extensive report available from The Survey Assocation in the UK. Although it focuses on Network RTK, there’s a valuable discussion in it regarding GLONASS. You can download the report here.

    Question #5: By 2020, is the DOD going to completely get rid of L2 signal?

    Gakstatter: No, not at all. L2 was never intended for use by the civilian community. However, in the 1980’s, some really smart scientists in the commercial sector figured out a way to gain access to the encrypted L2 signal via a technique is referred to as semicodeless.

    Since that time, the Department of Defense (DOD) has respected that technique because it’s been vitally important in the development of the GPS commercial markets. By respected, I mean they have intentionally not made changes to the GPS that would disrupt the semicodeless technique.

    The DOD has now has come to a point that dancing around the semicodeless issue has become a bigger liability than they want to assume. That’s understandable since L2C will allow dual frequency GPS receivers to utilize L2 without using semicodeless techniques, the DOD wants to be released of their liability with respect to L2 semicodeless.

    So, after December 31, 2020, the DOD will no longer guarantee that semicodeless receivers will operate as they do today. It is not a “brick wall” in that it will stop working at midnight on December 31, 2020. In fact, a semicodeless receiver may work perfectly fine most of the time after December 31, 2020, but if it stops working properly, the user assumes the liability.

    Off-topic

    One of the reasons my column is late this week is that I caught a bug earlier this week. It’s nothing serious; it’s just slowing me down a bit because I don’t have the energy I normally have. The fact is that I just don’t get sick beyond my tendency to attract strep throat once every few years.

    This year, I’ve opted out of the flu shot despite a specific call from my mother putting the heat on me to get one. I’ve never gotten a flu shot and probably never will. But, I do admit this is the first year I’ve actually considered it. At one point a few weeks ago, 25% of the primary and middle school-aged kids in our school district
    were absent due to illness. There were significantly fewer Trick-or-Treaters in our neighborhood this year; I believe due to illness.

    I’ve always made an effort to wash my hands, face, nose regularly (no, I’m not obsessive-compulsive) and pay attention to those around me when I’m in public places like malls, movie theaters and airplanes. I absolutely hate getting stuck sitting next to a person on an airplane who is coughing and sneezing. I remember specifically sitting next to a person on a flight back from Phoenix, Arizona, a half-dozen years ago. She looked like death warmed-over…coughing and sneezing horribly. Sure enough, the next day I could feel my body losing the battle. I ended up contracting strep. Ugh.

    Anyway, I want to remind you given that many of the US readers are traveling next week for the Thanksgiving holiday to take care of yourselves and your loved ones.  You’ll be traveling amongst those who haven’t escaped “the bug,” but have still decided to travel. Here are some tips from the Center for Disease Control and Prevention to keep you and your loved ones healthy.

  • GEOINT 2009

    The place to be if your job is intelligence and why what is where.

    By Art Kalinski

    When I was in graduate school at the University of North Carolina at Charlotte, Dr. Jerry Ingalls shared a succinct description of the “new” geography. He stated that old geography was merely the study of where everything was. However, new geography, with its spatial analysis tools, had significantly expanded the field of the study to “why what is where”  and knowing why we can start predicting new “wheres” based on known facts. That, of course, is where geospatial intelligence is today, and some of those tools and techniques identified the location of Iranian nuclear facilities long before they became public knowledge.

    IMG_0775Learning about the latest tools and techniques is the primary reason for conferences, and there is agreement in the geospatial community that GEOINT is the place to be. Organized by the United States Geospatial Intelligence Foundation (USGIF), attendance at the San Antonio conference was the highest it has ever been, according to USGIF President Keith Masback. Even with a weak economy, the over-arching opinion of all attendees was that the intelligence business will continue to grow regardless of world politics. By its nature, this conference really had many more “chiefs” than “Indians,” and many exhibitors spared no expense at the conference, knowing that they were reaching key decision makers.

    USGIF, a nonprofit educational organization created by the geospatial intelligence community, is the organizing force behind the conferences. There is heavy participation by the National Geospatial-Intelligence Agency (NGA) and other intelligence agencies, so the conference attracts top executives in the geospatial industry. The speaker and attendee list reads like a who’s who of the geospatial and intelligence fields.

    General Clapper, the Under Secretary of Defense for Intelligence, was a keynote speaker. He stated his belief that regardless of geopolitical decisions, he sees no decrease in the need for intelligence in Afghanistan and many other locations around the world. He further addressed the need for much faster turn-around of actionable intelligence and cited the joint efforts between the SIGINT (Signals Intelligence) and GEOINT (Geospatial Intelligence) communities.

    General Clapper discussed some of the work of the ISR (Intelligence, Surveillance, Reconnaissance) Task Force, which is seeking new technology and the Holy Grail of intelligence, automated target identification in complex environments. He also spoke about the benefits of commercial imagery sources and its use in an impressive NATO Fusion Center he toured.

    The second keynote speaker was Representative C. A. Ruppersberger, D-MD, chairman of the House Technical/Tactical Intelligence Subcommittee. The congressman addressed his concern that the U.S. is in danger of losing its preeminence in space because regulations are hampering development. He specifically addressed a need to overhaul International Trade in Arms Regulations (ITAR) that are hurting the U.S. commercial satellite industry. He also stated the need for additional research and development funding like the ones that built the U.S. space program and a greater emphasis on technical education. A troubling statistic he cited is that China has 440,000 engineers compared to the USA’s 65,000.

    Vice Admiral Murret, head of NGA, then spoke of his agency’s support not only for the military but humanitarian assistance in natural disasters such as flooding and earthquakes. He talked about the new NGA facility at Fort Belvoir and about how one third of his agency now works in St. Louis.

    In the exhibit hall close to 200 exhibitors demonstrated their latest efforts. Some highlights include:

    Cogent3D and Lockheed Martin demonstrated the release of GeoSketch, a plug-in for Google Sketch Up.  GeoSketch permits military users to build 3D models using the easy to use Google Sketch Up software. The tool permits users to import military UAV video imagery, oblique imagery, and other photo sources to rapidly build 3D models even if geo-referencing data or camera models are missing. The models can then be exported in common formats such as Google, Multipatch, or OpenFlight.

    Digital Globe announced the successful launch of its newest high-resolution satellite, WorldView 2. Imagery from the new satellite will be available in a few months, doubling Digital Globe’s image-collection capability, including multi-spectral imagery.

    LEXISNEXIS news open source highlighted the tremendous wealth of data that it makes available to intelligence analysts. Appistry and NJVC had extensive information on cloud computing and their ability to deliver mission-critical data, including legacy data, to users around the world.

    Pictometry and Lockheed Martin announced their alliance and creation of a new service, Intelligence on Demand (IOD). IOD promises to be a game changer. (See October’s column for details.)

    Every conference I attend there is always a new technology that really catches my eye.  Ball Aerospace was demonstrating such a technology, Flash LIDAR. Flash LIDAR has been a laboratory curiosity for a while but Ball Aerospace has made it a functional tool. Most current LIDAR collections use a laser to scan the ground with the return being sampled resulting in a collection of points on the ground that provide elevation data from which a DEM or contour lines are created. Although this is a rapid process it is sequential and not instantaneous.  The resulting data can be very coarse or fine depending on the sampling interval.

    Flash LIDAR is what the name implies; an entire area is imaged in one nano-second flash. The laser is diffused over an area and flashed once. The resultant image is a broad but dense sample taken at the same instant rather than through a scanning process. Since the image is taken from the same point at the same instant, the data can be used to create accurate 3D models. Those models can then be draped with photographic images or even video frames. The process is so fast that 3D models can be created almost in real time.

    The below images are a practical demonstration of the Ball Aerospace process using Flash LIDAR combined with a live video camera. As each frame of the video image is taken, a simultaneous Flash LIDAR image is also taken from the co-located LIDAR unit. The photo shows the live video and point representations of the Flash LIDAR 3D surface and the resultant 3D image draped on the moving 3D model.

    It’s hard to tell from these still 2D photos but seeing this system in operation was impressive since the Flash LIDAR and resulting 3D models were continuous and perfectly registered. The only limitation of this demonstration was that human flesh is not a good “Reflective Surface.” Note that in the photo the Ball representative was very animated. This stop-action screen-capture shows him as he jumped up.  In all cases the Flash LIDAR kept up with the dynamic movements.

    Point cloud.
    Point cloud.
    Point cloud.
    Point cloud.
    Point cloud.
    Point cloud.
    Wire-frame image.
    Wire-frame image.

    This was an impressive conference that suffered from too much in too short a time.  Two tools that were very helpful was a daily newspaper, the Show Daily, that recapped the previous day along with the current day’s schedule. It was published, printed, and placed under our doors as we slept. The other useful tool was a daily video show with key presentations and interviews for those that were unable to be in two places at the same time. It was available at several break locations and on our in-room TVs. This has been done at other conferences but not as well as the execution of USGIF.

    The USGIF team deservers a “Well Done!”

  • What’s the Difference between a Used Car Salesman and a GPS Salesman?

    Years ago, I heard a funny joke/maxim. I repeat it often and so do several others I know of so maybe you’ve heard it.

    “What’s the difference between a used car salesman and a GPS salesman?”

    Answer: The used car salesman knows when he’s lying to you.

    I didn’t attend the Minnesota GIS/LIS Annual Conference last week, but I received a report from someone who attended a session in which the presenter seemed to fit the maxim quite well. One of the presenter’s messages was that people should stop using WAAS immediately as a GPS correction source due to the inability of data collection software to handle the ITRF00 > NAD83/CORS96 datum shift. Following is a statement from one of his slides…

    “WAAS Real-time accuracy degraded because of datum shift”

    He claimed that users are “in a panic over it.” In all fairness, the presenter could have very well understood that the datum shift can be handled by a number of data collection software packages…just not the one he represents. After all, he works for a local distributor of GPS equipment. Or, even a scarier scenario would be that he really believed what he spoke.

    I’m not interested in naming names or company names of the offending party, but rather painting the true picture. Of course, the attendee I mentioned above knew better than to believe what the presenter was pitching. His group has been using WAAS as a primary correction source for a number of years and reconciling the datum shift between ITRF00 and NAD83/CORS96. It’s not that hard folks.

    Let’s review.

    ITRF00 is essentially the same as WGS-84(G1150) for sub-meter mapping purposes. WAAS (as well as EGNOS and MSAS) are referenced to ITRF00. You need to be aware that the definition of ITRF/WGS-84 has changed over time. Here is a link to a NIMA WGS-84 document that describes earlier versions of WGS-84 and here’s a link to the current version of WGS84 (G1150) that was adopted in 2002.

    In North America (my apologies to readers from other countries), the generally accepted mapping datum is NAD83. NAD83 has also changed substantially over time. Whereas the original WGS-84 was consistent with the original NAD83 (NAD83/86), today there is a substantial difference between the current WGS-84(G1150) and NAD83/CORS96 and also NAD83/NSRS2007. Here is a graphic from Joel Cusick of the U.S. National Park Service that gives you an idea of the difference over North America:

    Here is a link to a technical report from the National Geodetic Survey (NGS) describing the 14-parameter transformation from ITRF00/WGS-84(G1150) to NAD83/CORS96.

    Sadly and surprisingly, some data collection software today and even some PC-based “GIS” software still treat WGS-84 and NAD83 as the same. This instantly introduces a few feet of error. The irony is that people spend thousands of dollars purchasing high-performance GPS/GIS receivers capable of sub-meter accuracy only to introduce several feet of error by using software that improperly handles the datum transformation.

    What’s the solution if your software doesn’t handle the datum transformation properly?

    As mentioned above, WAAS is based on the ITRF00 datum and not NAD83/CORS96. As most base maps in North America aren’t referenced to ITRF, most likely you’ll need to transform your WAAS-corrected coordinates to NAD83/CORS96. This can be done one of two ways:

    1. As mentioned above, use GPS/GIS data collection software that handles the transformation correctly. This makes the transformation transparent, painless to the user and accurate in real-time.
    2. Apply a datum shift after you’ve collected your data. You can compute the shift by accessing an NGS datasheet near your project area (within 25 miles is close enough). Make sure it was occupied using GPS. Better yet, use coordinates from a CORS. The datasheet will report coordinates in both ITRF00 and NAD83/CORS96. Here is an example of coordinates from the CORS at Wisconsin Point, WI (near Duluth where the MN GIS/LIS Annual Conference was held):

    ITRF00 Position (Epoch 1997.0) – N 46 42 18.20201, W 092 00 54.760208

    NAD83/CORS96 Position (Epoch 2002.0) – N 46 42 18.17201, W 092 00 54.73394

    Simply enter the two coordinates into your favorite mapping software and you’ll be able to compute the distance and direction of the difference.

     

    Once you know this, you can apply the same offset to all of the data for your project. Quick and dirty? Yes. We’re not splitting hairs. WAAS isn’t delivering cm-level accuracy so this sort of transformation is more than adequate…and very efficient.

    The fact of the matter is that many, many organizations have adopted WAAS as a primary source of GPS corrections and are dealing with this datum transformation issue on a daily basis.

    GPS Constellation Management: Playing Not to Lose

    The WAAS/SBAS subject segues perfectly into the second subject of this column which is a follow-up of last week’s column on GPS Constellation Management.

    Last week, I failed to mention that SBAS (WAAS, EGNOS, MSAS) is a valuable contributor to RTK users. Although not designed specifically to aid RTK ground users, some GPS receiver designers have exploited the value of SBAS satellites to enhance RTK operations. In North America, there are two SBAS satellites. In Europe, there are two and there are two in the Japan region. Following is a graphic depicting the regional coverage of the SBAS satellites and their approximate location.

     

    In many regions of the world, users have at least one SBAS satellite available in view. The beauty of SBAS satellites for RTK is that, unlike GPS satellites, SBAS satellites are geostationary. The are available 24/7 as long as their signal path isn’t blocked by trees, terrain or buildings.

    Since using SBAS satellites for RTK is a relatively new innovation within the past couple of years, not all manufacturers have jumped on the bandwagon yet. The slow adoption of GLONASS was similar. This causes a problem when users want to mix and match RTK receivers from different manufacturers. For example, a user purchases an SBAS-capable L1/L2 RTK rover to be used with their existing L1/L2 RTK reference station. If their existing L1/L2 RTK reference station doesn’t support SBAS for RTK, then the feature on their new RTK rover is worthless.

    Even more important is the lack of support from RTN software designers. “No one’s asking for it” is the answer I get from RTN operators when asked if they are interested in supporting SBAS correctors in their RTN. I believe that users aren’t asking for it because users don’t have a clue how it would help them, and frankly, 99% don’t know the technology even exists. Now, if you would ask users if they’d be interested in one or two extra observables for RTK that would be
    available 24/7 in a geostationary orbit every day, I bet you’d hear some really positive answers.

    RTK users need to be able to utilize every observable that could help them. As Rob Lorimer and I reported last year in our market research report, machine control (based on RTK) will be the fastest growing GNSS segment over the period 2008-2012.

  • Expert Advice: GPS Constellation Maxed Out at 30

    Expert Advice: GPS Constellation Maxed Out at 30

    It appears that the GPS satellite constellation has a glass ceiling, so to speak.

    GPS was designed as a 24-satellite constellation, with four satellites in six orbital planes arranged to provide maximum observability around the globe. According to the government’s Space-Based Positioning, Navigation, and Timing website, “The U.S. government is committed to provide a minimum of 24 operational GPS satellites on orbit, 95 percent of the time. The U.S. Air Force launches additional satellites that function as active spares to accommodate periodic satellite maintenance downtime and assure the availability of at least 24 operating satellites. As of August 28, 2009, there were 35 satellites in the GPS constellation, with 30 set ‘healthy’ to users.”

    Figure 1 shows the locations of the 35 satellites. Green squares indicate satellites marked healthy in the broadcast almanac. The numbers displayed are the satellites’ pseudorandom noise (PRN) codes. Red squares, with PRN codes, indicate satellites transmitting L-band signals but currently set unhealthy. Note that SVN24/PRN24, although active, is not included in almanacs. Blue squares indicate reserve satellites with space vehicle numbers (SVNs) in parentheses. Notice the bunching together of certain pairs of satellites. The constellation of 30 healthy satellites is not configured to maximize geometrical performance. Rather it is to help guarantee a minimal level of performance considering that many of the spare satellites are one component away from failure. Basically, the 30-satellite constellation is actually being flown as a 24-satellite constellation.

    Figure 1. Locations of the 35 current GPS satellites: green squares denote satellites marked healthy in the broadcast almanac, satellites marked by red squares transmit L-band signals but are curerently set unhealthy, and blue squares indicate reserve satellites. Bunched pairs show satellites being flown in tandem.
    Figure 1. Locations of the 35 current GPS satellites: green squares denote satellites marked healthy in the broadcast almanac, satellites marked by red squares transmit L-band signals but are curerently set unhealthy, and blue squares indicate reserve satellites. Bunched pairs show satellites being flown in tandem.

    But with 35 satellites in working condition, why are only 30 set healthy? Modern GPS receivers can handle all 32 PRN codes, and many studies have shown the more satellites the better as far as position accuracy and reliability are concerned. In fact, a recent Air Force Space Command article stated, “One additional GPS satellite can make a difference between getting a degraded GPS signal and getting an accurate GPS-based location, whether it is for warfighters in Baghdad or firefighters in Boston.” The current control system should, in principle, be able to handle 32 healthy satellites.

    Ground Control System. But, according to the GPS Wing, the de facto limit is 31 satellites. We don’t know if this is a problem related to 2nd Space Operations Squadron (2SOPS) functions or if there is some military system or equipment platform that cannot tolerate 32 healthy satellites.

    Further, if the de facto limit is 31 satellites, why have we had only a maximum of 30 satellites set healthy since early this year? After all, 2SOPS rightly crowed about having 31 satellites set healthy for the first time on February 27, 2008, when SVN23 was reintroduced into the healthy constellation as PRN32.

    Figure 2, courtesy of Ted Driver at Analytical Graphics, Inc., shows the number of satellites set healthy from 1998 onward, according to the Notice Advisories to Navstar  Users (NANUs) issued by 2SOPS and the almanacs broadcast by the GPS satellites. Often, a satellite is actually set unhealthy for only a portion of the day, but this plot tallies only the number of satellites healthy for a full day. As we can see, off and on through most of 2008 and into 2009, we had 31 satellites set healthy on orbit. With 31 satellites, users benefited from better availability and accuracy and were slightly better able to handle the occasional three-satellite outages due to SVN35/PRN5 and SVN25/PRN25 being set unhealthy for extended overlapping periods.

    Figure 2. The number satellites set healthy since 1998 (courtesy of Analytical Graphics, Inc.)
    Figure 2. The number satellites set healthy since 1998 (courtesy of Analytical Graphics, Inc.)

    But since March 26, 2009, when SVN35/PRN5 was decommissioned from active service, we have not seen a return to 31 healthy satellites.

    Why is that?

    Ground Testing. I asked this question to Col. Dave Madden, the GPS Wing commander, during a panel discussion on GNSS program updates at The Institute of Navigation’s GNSS 2009 meeting in Savannah, Georgia, in September. Apparently, the reason why 31 satellites cannot currently be set healthy simultaneously has do with ground testing of Block IIF satellites. One PRN code is needed for the test satellite on the ground. Presumably this means that testing involves tracking the constellation in space and a IIF test satellite simultaneously.

    So, although everyone acknowledges that more GPS satellites are better, we have hit a 30-satellite ceiling. As IIF satellites are launched and further improvements are made to control system operations, and any incompatible old military systems are replaced or updated, perhaps we can break through this glass ceiling and have 31 or even 32 healthy GPS satellites available to users.

    We can hope.