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Survey and Mapping

October 31, 2007

Changdon Kee

Changdon Kee is a professor and associate head of the School of Mechanical and Aerospace Engineering at Seoul National University. He developed the basic concept and presented the first experimental test results of wide area differential GPS in the early 1990s.

Kee has published widely on GNSS, pseudolites, space mechanics and UAV Automatic navigation and control and holds more than 15 domestic and international patents for his work on GNSS.

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By Inside GNSS
October 21, 2007

Pat Fenton: GNSS from the Outside In

Patrick Fenton’s career as the guiding mind behind the design of six generations of breakthrough GNSS receiver technologies began the moment he realized his hobby — computer programming — might end the need for surveyors to spend long evenings reducing and verifying the data they collected each day.

Patrick Fenton’s career as the guiding mind behind the design of six generations of breakthrough GNSS receiver technologies began the moment he realized his hobby — computer programming — might end the need for surveyors to spend long evenings reducing and verifying the data they collected each day.

It was the summer of 1981. Fresh out of the University of Calgary’s survey engineering program, Fenton was enjoying a taste of what he’d envisioned would be a “professional outdoor career” as a rookie land surveyor for ShellTech Surveys, a now defunct division of Shell Canada.

“We would spend all day turning the angles and measuring for a road project,” he said. “Then, evenings we would spend hours reducing the data and making sure it was all correct. I was able to hop on the computer and get that done for the crew very quickly.”

Fenton’s inspired effort ended his work outdoors. “They told me to stay in the office and develop the software,” he recalled. “From then on I worked on processing the data and developing equipment that would make their jobs easier.”

When the oil crunch hit, ShellTech was sold in January 1982 and became Nortech Surveys Ltd. Fenton worked on a number of high-tech survey systems for the oil exploration industry, including INS, microwave ranging, and GPS. He became software manager of a Nortech subsidiary, Norstar Instruments.

“At the time, there wasn’t a suitable GNSS instrument on the market that met the needs of Nortech; so, the management decided that we had the talent to jump into the survey instrument business,” Fenton said. “We did create a very nice product; however, we lacked knowledge in high quality manufacturing. Each one we built was a little bit different.”

A Better Mouse Trap

NovAtel, then a giant in Canada’s cell phone industry, acquired the NorStar division in 1989.

“The combination of skills at NovAtel was exactly what was needed for our GPS products, that is RF, software and production engineers, DSP chip designers, and marketing experience,” Fenton said. “At NovAtel, we completely redesigned the receiver from the antenna down.”

At about the same time, Fenton hit upon an insight that led to an industry first: true sub-meter pseudorange positioning capability.

“I realized that the signal processing design and tracking loops within the GNSS receivers of that day were optimized for maximal signal power to signal processing complexity ratio,” he explained. “They were not optimized for range or carrier phase tracking accuracy — the elements driving position accuracy. It was during this period that I came up with the Narrow Correlator concept.”

His invention, commercialized into the GPS1001 receiver in 1991, was five times more precise than the previous technology. It received the Better Mouse Trap Award that year from the Institute of Navigation (ION).

Today Fenton is vice-president and chief technology officer (CTO) for NovAtel, which has become a leading provider of GPS and augmentation components and subsystems designed for rapid integration into an endless variety of high precision, commercial applications.

At the tender age of 49, he holds 15 patents and has authored more than 20 technical articles for the ION. So significant are his contributions to the evolution of GNSS that his peers have recognized him with the ION Satellite Division’s highest honor: the Johannes Kepler Award.

Fenton is also known for projects that have significantly improved receiver capability to allow reliable positioning and precise navigation even in obstructed environments where GPS alone doesn’t work. Marine, mining, precision agriculture, and surveying and mapping are among the applications benefiting from such advancements.

On the Fast Track

For example, he has spent several years leading a small team that is integrating inertial measurement units with NovAtel’s GNSS receivers. The results of their success using digital terrain modeling (DTM) techniques to improve precise position output availability are showcased during telecasts of NASCAR and IndyCar races.

“Our challenge was to provide Sportvision a continuous stream of time-tagged position and velocity measurements from each race car,” Fenton said. “Sportvision uses this information to annotate the TV camera image stream with details such as the driver’s name, speed, and lap time while the race is underway.”

Sounds simple enough. But NASCAR tracks presented formidable challenges for radio frequency coverage, the lifeblood of GNSS technology.

“In addition to lots of steep bleachers there are cat walks around and over the track,” Fenton explained. “Probably the worst obstacle was the steel mesh catch fence that completely surrounds and overhangs the track. When the cars are up against the wall, more than half the sky is blocked by the catch fence.”

No sky, no satellite coverage. Not only that, but the tracks are very short. Laps can take as little as 15 seconds. “When a car is halfway around the track, it has blocked the other half of the sky. In this case, as a result, we could never lock in a satellite for more than 10 seconds.”

Using a DTM of the NASCAR track, Fenton’s team was able to constrain a car’s position. “This algorithm acted like an additional satellite and improved the availability substantially,” he explained. “But it wasn’t until we added integrated IMUs [inertial measurements units] that we were able to deliver 100 percent position and velocity availability.”

Fenton’s hallmark is a knack for finding and integrating technologies that drive powerful new applications. During the mid-1990s, as he rose from chief engineer to director of research and development, he was instrumental in NovAtel’s acquisition and commercialization of the MEDLL (Multipath Estimation Delay Lock Loop) technology, licensed from Delft University. WAAS, the U.S. Federal Aviation Administration’s Wide Area Augmentation System, and the European Geostationary Navigation Overlay Service (EGNOS) use it.

This powerful combination of scientific chops and market acumen earned Fenton a vice presidency in 1997 and the additional title of CTO in 2003. He was appointed to NovAtel’s board of directors in 2005.

The company’s latest generation OEMV series of GNSS receivers, released last year, illustrates the exponential changes in core technology that occur between versions. NovAtel’s “system on a chip” now has more than four million gates, almost eight times as many as its predecessor.

Fenton, who grew up in Canada’s capitol (Ottawa) has retained his zest for the outdoors including a passion for photography. He met his wife Tanis through her brother, a skiing buddy. They have three children; two in college and one in high school, and the entire family takes full advantage of Alberta’s rich recreational opportunities.

But even in the remotest glacier field, Fenton never completely loses touch with GNSS. Each winter he and a group of friends rent a backcountry hut and helicopter in for a week of alpine skiing. “Four times in our lives we’ve been up in a whiteout,” Fenton said. “We were able to navigate back to the hut with GPS.”

Fenton’s coordinates:
N51 06’ 59” W114 02’ 18”

COMPASS POINTS

Engineering Specialties
System conceptualization, GNSS receiver design and signal processing, multipath mitigation techniques, and firmware development.

His Compass Points
• Home and family: wife Tanis and three children, household activities, weekend trips, summer vacations, extended family, and friends
• Career: applied technology, mentoring, teamwork, business relationships, learning, and change
• Hobbies: photography, and outdoor activities

Favorite Equation
This formula is a derivative of the Central Limits Theorem. It’s a simple formula but I use it all the time to estimate expected signal-to-noise ratio levels at the output of hardware correlators at various stages of designing GNSS receivers.

GNSS “Aha” Moment
In the summer of 1985, I started developing position processing software from data Nortech had collected from their various survey operations. I realized that I could make a significant contribution.

First Significant GNSS Achievement
I came up with the Narrow Correlator concept. This technique made for a five-fold improvement in pseudo range accuracy, leading the way to reliable sub-meter positions.

GNSS Mentor
Probably the single person that I’ve learned the most from in GNSS over the years is Dr. A.J. Van Dierendonck. He was the chief scientist with Stanford Telecommunications Inc. where we were sourcing GPS receiver channels for the first GPS product I was involved with in 1986. He has been a technical consultant with us, periodically, for nearly 20 years.

GNSS Event that Most Signifies That GNSS had “Arrived”
I think the first Gulf war with all the publicity and TV images of the smart weapons provided a huge boost to the popularity and awareness of GNSS. Before that time, I always had to explain what GPS was. After that time, everyone seemed to have a good appreciation for what GNSS was.

Influences of Engineering on His Daily Non-Work Life
My engineering mind is always churning. For example, over the last couple of years my wife and I built an energy-efficient house. I was heavily involved with all the engineering aspects of that; producing all the CAD construction drawings, design of all the mechanical systems including the in-floor geo-thermal heating system, and the networks for phone and internet connectivity to all the rooms.

Popular Notions about GNSS That Most Annoy
The notion that GNSS will work deep indoors, under ground, or under water – perhaps for oil exploration at the bottom of a drill tip or for diving. If you can’t pick up FM radio, then most likely your GPS won’t work.

Favorite Non-GNSS Activities
Winter: skiing, snowboarding, alpine touring
Spring/Summer/Fall: cycling, canoeing, camping, sailing, fly fishing
All seasons: photography

What’s Next
There are several possibilities. The first would be multi-constellation, multi-frequency GNSS. This is where a single receiver tracks multiple satellite constellations (GPS, Galileo, GLONASS, etc.) and provides a blended robust position solution. The second may come from time of arrival (TOA) positioning of cellular phone tower signals. The density of cell phone towers is continuing to increase. At a certain point, the use of TOA processing of cell signals will rival consumer GPS for the large urban and indoor markets.

By

Allison Kealy: The Remarkable Art of the Possible

Allison Kealy caught the GNSS bug at age 18 while waiting beneath the starry skies of Trinidad for the moment when enough satellites would become available to allow an Ashtech receiver to compute her position. Up to that point, her training as a surveyor was limited to land-based equipment.

Allison Kealy caught the GNSS bug at age 18 while waiting beneath the starry skies of Trinidad for the moment when enough satellites would become available to allow an Ashtech receiver to compute her position. Up to that point, her training as a surveyor was limited to land-based equipment.

“It was 1990 and we were standing in the middle of nowhere, in the middle of the night, which was the only time you could use GPS then,” Kealy recalled. “It took a lot of imagination to see that we really were on the edge of cutting technology. More than 10 years later we were standing at the same spot, talking about GLONASS and GALILEO.”

During that time Kealy’s interest in technology and GNSS propelled her from her birthplace in Trinidad, a village of approximately 10,000 called Penal, to the UK’s University of Newcastle for a doctoral degree in geodesy. Ultimately, the journey led her to the University of Melbourne in Australia where, in 1999, she was the first woman appointed to an academic position in the Department of Geomatics.

Mapping Australia’s Aboriginal Art

Her pioneering spirit is perhaps most evident in her contributions to an exceptional project cataloguing some 50 Aboriginal paintings at Australia’s iconic Uluru (Ayers Rock). In 1985 ownership of Ayers Rock was returned to the local Anangu people who consider it sacred and have called it Uluru (pronounced oo-luh ROO) for at least 40,000 years. In 1987, Uluru National Park was declared a World Heritage site.

At the request of the Anangu, a team of Melbourne scientists including Kealy was enlisted to create a digital record of the rock art. “To create a map that would allow us to establish a historical record, we needed to get the coordinates so it would be possible to revisit the sites in the future,” Kealy said. “Some of the art is located in places that GPS alone won’t reach. The team was keen to investigate the use of combined GPS and GLONASS receivers; so, I came along to run that part of it.”

Their task was complicated by the secrecy surrounding many Aboriginal sites and the need to minimize their movement on the massive landform out of respect for the Anangu, who do not climb Uluru because of its great spiritual significance. The team was granted a unique exception in order to gain access to paintings located within the walls of the enormous red sandstone monolith, which rises abruptly more than 300 meters above the Australian plains and stretches nine kilometers around its base. When viewed from a jet, Uluru resembles a colossal Paleolithic cutting tool pointing eastward.

“Some sites are considered very sacred and are not accessible to the public,” Kealy said. Some are accessible only to men, some only to women, some only to women who have had children.”

The Melbourne team was nearly stymied by cross-cultural communication gaps.

“At one point our Anangu guides thought that the GPS was like satellite transmissions,” said Kealy, whose efforts to undo misunderstandings included scratching illustrations into the dirt to show how the technology worked. “They were afraid we were beaming the images elsewhere. It took a lot of work to convince them otherwise. You didn’t want to abuse the trust and you weren’t sure what the protocols were. An Aboriginal woman who worked for the parks service helped me become more aware of what was going on.”

Fostering a Tradition of Innovation

The Uluru project was done in 2000, the same year that Kealy received The University of Melbourne’s prestigious Universitas 21 Fellowship for Excellence in Teaching and Research. The following year she received the prize for the best research paper at the Institute of Navigation (ION) international conference in Salt Lake City. And she had yet to celebrate her 30th birthday.

Currently she is supervising the doctoral work of eight men and women. In less than six years her lab has published an impressive number of articles in international journals. At the same time, her work developing interactive multimedia environments for teaching satellite positioning and integrated systems in geomatics has won grants and accolades.

Kealy and one of her students, Stephen Scott-Young, were the first Australians to win a BMW Scientific Award for developing a driver’s aid capable of compensating for zero visibility due to whiteout conditions, pea soup fog, or the torrential rains common in tropical places like Kealy’s native Trinidad.

“This is an in-car navigation screen that gives you a graphical image of what is ahead so you can see the edge of the road, the center line, and where you are relative to the other the markers on the road,” she explained. “We also did some thinking about having other cars equipped to give information about their locations as well.” When Scott-Young finished his Ph.D. in 2005, he received an ION student award for his work on the project.

Kealy credits her mentor and Ph.D. advisor, Paul Cross, with igniting her own enthusiasm about teaching and research. Cross is department head and Leica Professor of Geomatic Engineering at University College in London.

“He was quite enthusiastic about what he was doing and was very patient and encouraging with me,” Kealy said. “He inspired me to look at situations where GPS didn’t work, and to think about ways of integrating of GPS with other technologies. He demonstrated that success wasn’t only about knowing your stuff, but that it was just as important to build relationships with people.”

The ability to imagine alternatives continues to guide Kealy’s reactions to requests for using GPS in new ways. Recently she became involved in a project for an Australian company that supplies drug addicts with clean needles.

“They want to do a documentary showing the life cycle of one of these packs of disposable syringes,” she said. “They were looking for a tracking technology for this application. GPS won’t work in the way that they originally envisioned, but we are coming up with combinations of technologies that can be used to track the packs.”

Kealy expects the future to bring applications that may seem extreme now – but then, she can remember wondering at the notion that satellites would soon render land-based surveying stations obsolete.

“It’s hard not to feel very humbled by the opportunities I’ve had,” she said. “Sometimes the research that you do when you’re in a more developed country seems like a luxury. I give my teachers in Trinidad a lot of credit for getting me started.”

Kealy’s coordinates:
37° 48’ 00.228”S 144° 57’ 38.460E

COMPASS POINTS

Engineering Specialties
Sensor fusion and measurement integration

Her Compass Points

  • Aidan, her 11-month-old son
  • England, where she earned her doctoral degree in geodesy and met her husband, Tim, a rheologist from Ireland
  • Trinidad, her home country
  • Australia, where she is the first woman appointed to the geomatics department at The University of Melbourne

Mentor
Paul Cross

“He is incredibly inspirational. He visited Trinidad the year that I finished my undergraduate degree. He was and still is quite visionary about satellite positioning.”

Favorite Equation
Weighted least squares estimation

x = (ATWA)-1 ATWb

GNSS Event That Most Signified that GNSS has “Arrived”
“Geocaching”

Popular Notion About GNSS That Most Annoys
“That you don’t need to understand GNSS to use it – just switch on a receiver and off you go. Current generation GNSS still has its limitations.”

Current Research
Through 2008 Kealy is part of several research teams working towards improving the quality estimates provided for real-time positioning applications; enhanced atmospheric modeling for extending the range of centimeter level real-time positioning across CORS networks; GNSS for real-time weather forecasting and integrated positioning for augmented reality applications.

Influence of Engineering on Her Daily Non-Work Life
“I’m a big fan of ‘if you work with technology you must live it.’ I surround myself with technologies that are designed to make life easier.”

Favorite Non-GNSS Activities
“Spending time with my family and traveling.”

On Being a New Mother
“I’m treating it like another research project, going through the process of figuring it out as it goes along. With no instruction manual or 24-hour technical support line it’s a challenge. I’m back to work full time now and lucky to have a fantastic husband and very supportive colleagues and friends.”

Human Engineering is a regular feature that highlights some of the personalities behind the technologies, products, and programs of the GNSS community. We welcome readers’ recommendations for future profiles. Contact Glen Gibbons, glen@insidegnss.com.

By Alan Cameron

October 14, 2007

Precise Point Positioning and Its Challenges, Aided-GNSS and Signal Tracking

Q: What is precise point positioning (PPP), and what are its requirements, advantages and challenges?

A: Precise point positioning (PPP) is a method that performs precise position determination using a single GPS receiver.

This positioning approach arose from the advent of widely available precise GPS orbit and clock data products with centimeter accuracy. These data can be applied to substantially reduce the errors in GPS satellite orbits and clocks, two of the most significant error sources in GPS positioning.

Q: What is precise point positioning (PPP), and what are its requirements, advantages and challenges?

A: Precise point positioning (PPP) is a method that performs precise position determination using a single GPS receiver.

This positioning approach arose from the advent of widely available precise GPS orbit and clock data products with centimeter accuracy. These data can be applied to substantially reduce the errors in GPS satellite orbits and clocks, two of the most significant error sources in GPS positioning.

Combining precise satellite positions and clocks with a dual-frequency GPS receiver (to remove the first order effect of the ionosphere), PPP is able to provide position solutions at centimeter to decimeter level, which is appealing to many applications such as airborne mapping. PPP is different from double-difference RTK (real-time kinematic) positioning that requires access to observations from one or more base stations with known coordinates. The word “precise” is also used to distinguish it from the conventional point positioning techniques that use only code or phase-smoothed code as the principal observable for position determination.

(For the rest of Yang Gao’s answer to this question, please download the complete article using the PDF link above.)

Q: Does Aided-GNSS improve signal acquisition, tracking, or both?

A: A-GPS (Aided/Assisted-GPS) and more recently its extensions, A-GNSS, have been introduced to substitute for missing satellite broadcast data when access is intermittent, difficult, or impossible due to signal obstruction. It has expanded the capabilities of the traditional receiver in reducing the time to first fix (TTFF), enabling “high sensitivity” modes, improving the performance in urban canyons and indoors, and incidentally, boosting the receiver’s efficient use of power.

Multiple ways have been developed to deploy an A-GPS server, and to distribute the process flow between the server and the mobile. The mobile station–based method places the position determination in the receiver, while the network-based method relegates it back to the server.

Other notable factors influence the architecture. The assistance can be one-way, where information accessible at the server flows down to the receiver, or in closed loop, where the information is uploaded to the server, processed remotely applying far larger computational resources and extra knowledge not available to the receiver, and then pushed back to the receiver in its final form.

We will now introduce two simple rules that will illustrate the rest of the explanations:

Rule 1: For A-GPS to be practical, the assistance information should not be stale when ready to be used at the mobile. In more technical terms, the assistance information persistence needs to be longer than the sum of network latency plus server and mobile processing times,

Rule 2: In a closed loop architecture, the information collected at the mobile, and processed at the server should be returned fast enough before the internal state of the mobile changes too much. We can reformulate it as the sum of the round trip network delay plus server and mobile processing times have to be shorter than the process time constant to control the mobile.

(For the rest of Lionel J. Garin’s answer to this question, please download the complete article using the PDF link above.)

By

A New Version of the RTCM SC-106 Standard, the Probability of Solving Integer Ambiguities

Q: The RTCM has announced a new version of its widely used differential GPS (DGPS) standard. Why did the group decide a new standard — Version 3 — was needed, and what are the benefits compared to Version 2?

Q: The RTCM has announced a new version of its widely used differential GPS (DGPS) standard. Why did the group decide a new standard — Version 3 — was needed, and what are the benefits compared to Version 2?

A: Initially, the RTCM (Radio Technical Commission for Maritime Services) Subcommittee (SC104) Version 2 standard was developed with marine DGPS as the target application. One of the design goals for the RTCM SC 104 standard was to have correctional information readily available for user equipment. The outlines of the messages were specifically tailored for low bit rate data links.

Not until the beginning of the 1990s did RTK (real-time kinematic) surveying applications come into focus for RTCM. The committee drafted new RTK messages based on the proven DGPS messages. Although the DGPS messages only contain corrections, the RTK messages also allow transmission of raw observables from the satellite signals. RTCM tentatively published redundant means of disseminating precise RTK information with the aim of gaining practical experience during their implementation.

The first implementations by different manufacturers had diverse interoperability issues. For instance, various manufacturers have different sign conventions for representing the carrier phase observations, which resulted in incompatibilities when mixing receivers of different manufacturers.

(For the rest of Dr. Hans-Jürgen Euler’s answer to this question, please download the complete article using the PDF link above.)

Q: What is the probability of correctly resolving integer ambiguities and how can it be evaluated?

A: Resolving, or “fixing”, carrier phase ambiguities to integer values is ultimately based on statistical assumptions and testing. As such, a probability is associated with resolving any particular ambiguity correctly. Evaluating the probability of correct fix (PCF), that is, the probability that the ambiguities are fixed to the correct integer values, is particularly important for safety-critical applications where an incorrect ambiguity fix would produce hazardously misleading information (HMI).

In fixed-ambiguity carrier phase processing, the usual procedure is to begin by estimating the carrier phase ambiguities as real-valued (“float”) parameters and then to determine their integer values. A difficulty with this method is that, although the least-squares adjustment or Kalman filter used to estimate the real-valued ambiguities provides an estimate of their quality (a covariance matrix), it is not obvious how to obtain an estimate of the quality of the integer ambiguities.

In most carrier phase ambiguity estimation methods, integer quality is validated using some sort of statistical test. These generally involve testing the least-squares sum-squared residuals of the best fitting integer solution against the second best fitting solution. The test statistic is then compared against a threshold value, the idea being that if the best solution is sufficiently better than the second-best solution, then it must be correct.

(For the rest of Kyle O’Keefe and Mark Petovello’s answer to this question, please download the complete article using the PDF link above.)

By
September 19, 2007

NavCom Tech L1 GPS RTK Receiver

NavCom Technology offers its new SF-2110M and SF-2110R modular L1 StarFire GPS receivers. The SF-2110M has an integrated, compact dual-band antenna capable of receiving GPS and StarFire signals from NavCom’s global satellite-based augmentation system. The SF-2110R includes a separate L-Band antenna for enhanced StarFire signal reception in challenging environments and at high latitudes, according to the company. NavCom Technology Inc., Torrance, California USA.

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By Glen Gibbons
August 20, 2007

Trimble Dimensions 2007

Trimble innovations that target the surveying, construction, engineering, and mapping professions, organized into more than 200 educational sessions in multiple specialty tracks. Keynote speakers include Trimble President & CEO Steven Berglund, Dr. Robert Ballard, explorer and discoverer of the wreck of the Titanic, and Peter Hillary, mountaineering explorer.

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By Inside GNSS

GNSS Workshop

“Global Navigation Satellite Systems: Problems, Vulnerabilities and Solutions” is the theme of an international workshop jointly organized by the Royal Institute of Navigation (RIN) Croatian Branch and the Institute of Engineering Surveying and Space Geodesy, University of Nottingham, UK. This three day event will focus in particular on developments aiming to improve the accuracy of GNSS, including augmentation systems such as WAAS/EGNOS and networked RTK systems. For more details, contact Dr. Renato Filjar below.

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By Inside GNSS
July 2, 2007

GPS + GLONASS for Precision

The SC Geodetic Survey (SCGS) has combined the technologies of the GPS, GLONASS, cellular communications and high-speed server networks to provide centimeter-level accuracy in real-time for surveying, mapping, and engineering applications.

The SC Geodetic Survey (SCGS) has combined the technologies of the GPS, GLONASS, cellular communications and high-speed server networks to provide centimeter-level accuracy in real-time for surveying, mapping, and engineering applications.

Named the SC Virtual Reference Station (VRS*) Network, the system is composed of 45 global navigation satellite system (GNSS) receivers installed statewide and connected by high-speed Internet to servers in the state capital, Columbia. Users connect in the field via cellular digital data communications to access the servers and obtain near real-time custom corrections to position objects or automate vehicle operations.

The South Carolina Department of Transportation has partnered with the SCGS with the intention of using the VRS for machine control to automate highway construction. South Carolina is the only state in the nation to use this technology to include the Russian GLONASS satellites as well as GPS satellites for a more robust solution.

Important to the implementation of the VRS is the provision of a common and consistent connection to the North American Datum NAD83 (2007) via the South Carolina State Plane Coordinate System. All coordinates produced through the use of VRS can be directly tied to NAD83 (2007). Surveyors and engineers will no longer need to be concerned about datum issues and coordinate conversions.

This article will describe how SCGS, which operates within the state Budget & Control Board’s Office of Research and Statistics, designed, implemented, tested, and operates the GNSS VRS network today.

(For the rest of this story, please download the complete article using the PDF link.)

By
May 1, 2007

Ruth Neilan: The Global Grid Master

Ruth Neilan outside the history library at the GeoForschungsZentrum in Potsdam, Germany.

When Ruth Neilan was named director of what is now known as the Central Bureau of the International GNSS Service (IGS), she had an immense undertaking before her.

A voluntary civilian federation, the IGS compiles and analyzes GPS (and more recently, GLONASS) satellite data. From these, the IGS creates highly accurate products —such as precise satellite orbit and clock files — and makes them freely available to engineers, scientists, and researchers all over the world.

When Ruth Neilan was named director of what is now known as the Central Bureau of the International GNSS Service (IGS), she had an immense undertaking before her.

A voluntary civilian federation, the IGS compiles and analyzes GPS (and more recently, GLONASS) satellite data. From these, the IGS creates highly accurate products —such as precise satellite orbit and clock files — and makes them freely available to engineers, scientists, and researchers all over the world.

The latter folks use the IGS data to improve the accuracy of their own GNSS positioning and timing results based on observations from the same set of satellites, using IGS products in place of the broadcast data.

Originally known as the International GPS Service for Geodyanmics, the standardized global tracking network was initiated by NASA and NOAA in the late 1980s. Today, the IGS Central Bureau is managed by NASA’s Jet Propulsion Laboratory (JPL) at Caltech in Pasadena, California, where Neilan has worked for nearly 25 years. IGS has 200 participating organizations —mostly public, government, and research agencies — with upwards of 400 permanent ground stations and data and analysis centers in more than 80 countries.

But in the early 1990s, all of that was far in the future. Neilan and the IGS had to create the building blocks themselves: setting standards, agreeing upon specific formats for data collection and processing, deciding how much to log to guarantee the precise results they needed. They succeeded in great part because of Neilan’s passion and optimism that GNSS technologies could — and do — bridge geopolitical boundaries.

“Through IGS, developing countries can join an international effort. People are very enthusiastic about contributing,” she said. “Off-the-shelf products have developed to such a point that they can leapfrog into the highest technology that’s available. The difficulty we have is getting enough resources to put their efforts on solid ground and ensure sustainability.”

Never Say “Never”

Neilan’s internationalist bent was established early in life.

She recalls crawling beneath the drafting tables in her father’s engineering firm in Somerset, a small Appalachian town in southwest Pennsylvania, and losing herself in books. She especially like the one with fascinating photographs of Asia and, in fact, went on to study Mandarin Chinese for five years.

As a child, she was convinced that she would “never” be an engineer. But blessed with a surefire sense of direction that she calls “Zen navigation,” Neilan loved reading maps and making precise measurements.

At college, she gravitated to The Pennsylvania State University’s engineering technology program, earned an associate’s degree, and became a surveyor. But she still wasn’t convinced that engineering should be her life’s work, so she took a detour.

A two-year globe-spanning tour started her on the path that combined her passion — Asia and the world — with what turned out to be her calling: engineering and the development of GNSS.

On her sojourn Neilan crossed Turkey and Afghanistan, worked as English editor for a Taipei magazine, climbed to the Mount Everest base camp, and attained an altitude of 19,200 feet— without oxygen — while crossing into the Rowalling Valley along the Tibetan border. Along the way, Neilan realized she was good at engineering.

She returned to the United States to earn a bachelor’s degree in civil and environmental engineering plus a minor in Asian studies, graduating with distinction from the University of Wisconsin at Madison in 1983.

Although the buzz about GPS began perking in the early 1980s, nothing was taught at the university level. After graduating, Neilan visited a friend at the Jet Propulsion Laboratory at California Institute of Technology in Pasadena, California. Hoping for nothing more than ideas for a thesis topic, Neilan arrived wearing flip-flops and shorts. She met with several people working on GPS and, by the end of the day, she had a job.

She put herself on what she laughingly refers to as the first in a series of “five-year plans,” working for JPL while pursuing her master’s degree. She finished her thesis, “An Experimental Investigation of the Effect of GPS Satellite Multipath,” in 1986.

Growing the Global Grid

Neilan’s first major project out of graduate school put her at the hub of the emerging GPS infrastructure. JPL assigned her to get the Deep Space Network’s first GPS receivers and meteorological instrumentation up and running. As that project unfolded, she also managed seminal projects measuring crustal deformation, tectonic motion, and earthquake fault monitoring using GPS techniques.

Starting in 1990, a planning group of five leaders — including Neilan and her mentor at JPL, Bill Melbourne — began meeting to plan the way forward for a global network. Neilan led implementation and operation of ground data systems for the GPS Ground Tracking Network. At about the same time, she also took on the separate task of coordinating the sub-network of six GPS tracking stations required for mission support of the GPS precise orbit determination experiment flown on the satellite TOPEX/Poseidon.

In 1992, she became GPS Operations Manager for the NASA/JPL global network and for scientific support of regional experiments, overseeing project management and technical direction of field engineering for NASA scientists and geodetic tasks at the University NAVSTAR Consortium (UNAVCO) in Boulder, Colorado.

One year later, she was named director of IGS.

The Global Grid and Beyond

Neilan’s serves on the advisory board of the U.S. Positioning, Navigation and Timing Executive Committee, which addresses such issues as policy, planning, management, services, capabilities, and funding.

“This board provides an additional assurance that there is a voice for users,” Neilan says. “The board includes international people, which emphasizes the global nature of GPS.” It also underscores the value that the executive committee places on the international community as part of the process, she adds

Since 2005 she also has served as vice chair of the Global Geodetic Observing System, which provides continuous, precise observations of the three fundamental geodetic observables and their variations: the Earth’s shape, gravity field, and rotational motion. She says a stable, sustainable global reference frame is crucial for all Earth observation and for practical applications ranging from agriculture to the dynamics of atmosphere and the oceans.

The system is beginning to help scientists get their arms around the complexities of seismic activity and climate variation. “Natural hazard detection and mitigation is a really important use of GPS and continuous networking,” Neilan says. “Less than a day after the earthquake that triggered the tsunamis in the Indian Ocean in 2004, we could see that our IGS station in Singapore had moved almost an inch. Our IGS stations in India also had moved.”

Neilan’s zest for travel makes her an ideal fit for her job, which requires frequent trips to developing countries. She lights up when talking about bringing Africa’s 50-plus nations into the grid. This effort, known as AFREF (which stands for unification of African Reference Frames) includes vertical data as well as gravity observations. However, she emphasizes that planning on a continental scale does not have to be “top down or all at once.” Instead, she focuses on assisting newcomers put in GPS systems that meet standards and follow conventions used by the rest of the world.

If Neilan had just one magic GNSS wish, it would that everyone understood the importance of tying into the global grid, known officially as the International Terrestrial Reference Frame. “It’s easy to remotely sense an area, but often contractors or consultants set up their own little local reference system,” she explains. “Then, when they try to link up or extend their project, it has no relationship to the country’s grid, much less the international grid. It’s been very hard to get this across to the mapping and GIS people.”

NASA’s return to space exploration opens up the possibility of extending GPS-like constellations to the Moon and to Mars. “We need to have a way of commonly and seamlessly referencing all the vehicles,” Neilan says. “An extended coordinate timing system would reduce errors.”

Neilan’s daily contacts with colleagues around the globe reinforce her optimism that GNSS technologies can bridge geopolitical boundaries.

“Open availability [of data] is seeding so much innovation and fostering better understanding of our world,” she says. “IGS is the global sandbox. Everybody can have fun and play.”

Neilan’s coordinates:
34° 12′ 5.7" N
118° 10′ 27.47" W
h = 372 meters

Ruth Neilan’s Many GNSS Hats

  • Vice Chair, Global Geodetic Observing System (GGOS) since 2005
  • Director, Central Bureau of the International GNSS Service (IGS), since 1993
  • Advisory board, US Positioning, Navigation and Timing (PNT) Executive Committee
  • Ad Hoc Strategic Committee on Information and Data (SCID), International Council for Science (ICSU)
  • International Committee on GNSS (ICG), representing the International Association of Geodesy (IAG)
  • Executive Committee, International Association of Geodesy
  • IGS website http://igscb.jpl.nasa.gov

COMPASS POINTS

Engineering Specialties
Surveyor, geodetic surveying, and civil and environmental engineering.

GNSS Mentor
Bill Melbourne at the Jet Propulsion Laboratory, a visionary who’s many accomplishments included leading GPS technology developments at JPL. “His support in shaping the GPS global network and working with our international partners laid the foundation for the IGS.”

Favorite Equation
Geoid Separation H=h-N

Heights that are given from GPS (h) are relative to the GPS ellipsoid WGS84. “To get the vertical position of a point, the separation between the geoid and the ellipsoid (N) must be known — with care. You can think of the geoid as the surface of the earth approximated by the mean sea level.”

Her Compass Points
Neilan credits her family first – her “brilliant” jazz pianist husband, “terrific” kids, and parents who “are always there, even for GPS observations in American Samoa, Easter Island, and remote areas of Mexico.” Her other compass points are “the wonderful IGS/GNSS community of colleagues and friends,” and “The great game — soccer!”

Fell in love with GPS when . . .
. . . she realized that this revolutionary technology could provide precise position and navigation aids for anyone, anywhere, anytime. “(This) levels the playing field to an extent — especially in the developing countries.”

Knew GNSS had arrived when. . .
. . .
CASA UNO ’88 deployed the first civilian global tracking network for orbit improvements to monitor crustal deformation at many stations in Central and South America. “This was the first large-scale study of crustal deformation. Now it is done continuously for hundreds of stations around the globe.”

Influences of Engineering on her Private Life
“Time motion studies in the kitchen!”

Popular Notions about GNSS that Most Annoy
“That GPS will operate according to specifications when actually it is far, far better than that. We need to develop the notion of performance-based capabilities and delivery of services.”

What’s next?
For Neilan and IGS, this includes integrating the upcoming signals from GALILEO, COMPASS and other new GNSSes into the mix. They are aiming for seamless incorporation to take advantage of the signals “so that we can use this technology over several decades in order to better understand our changing world.” And, as always, IGS’s on-going effort to promote dialog and a forum for the international use of GNSS.

Human Engineering is a regular feature that highlights some of the personalities behind the technologies, products, and programs of the GNSS community. We welcome readers’ recommendations for future profiles. Contact Glen Gibbons, glen@insidegnss.com.

By
January 31, 2007

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