NDGPS Gasping

June 27, 2007  - By
Image: GPS World

RITA and the Coast Guard have a tough job ahead. Between them, the Department of Transportation’s (DOT’s) Research and Innovative Technology Administration and the multi-mission maritime service are trying to save a national differential GPS (NDGPS) program that faces termination next year.

History. The U.S. Coast Guard (USCG) implemented the concept in the mid-1990s. Their requirement was for marine navigation, and the system now provides service for coastal coverage of the continental United States, the Great Lakes, Puerto Rico, portions of Alaska, Hawaii, and a greater part of the Mississippi River Basin. In a testament to NDGPS’s success, many countries around the world have duplicated the concept.

Since the DGPS signal is broadcast in a 360-degree radius, inland users close enough to the USCG broadcasting station can receive and use the corrections. All of this happened before SA (Selective Availability) was turned off, so the accuracy improvement was staggering; from 100 meters down to 1-3 meters. Once inland users tasted the sweetness of the USCG DGPS system, a groundswell of support arose for expanding the system inland. The NDGPS system was born.

Manufacturers began to integrate “Coast Guard” DGPS receivers into their products. Companies like CSI and Starlink offered after-market DGPS receivers to enable virtually any GPS user to receive the free DGPS signal, whether it was a $200 consumer GPS unit or a $10,000 submeter mapping receiver. Since then, tens of thousands of “Coast Guard” DGPS receivers have been sold around the world.

Between the USCG, the Army Corp. of Engineers (USACE), and the DOT, 86 stations now blast out DGPS corrections free of charge that cover more than 90 percent of the U.S. landbase.

Trouble. The program ran smoothly through the first half of this decade. Each year, a few new stations were added to expand coverage. The HA (High Accuracy)-NDGPS concept to provide decimeter-level positioning was proven to work. However, the rug flew out from under NDGPS last year when DOT’s Federal Railroad Administration (FRA) announced it would no longer sponsor NDGPS. NDGPS supporters had long hung their hats on Positive Train Control (PTC) as the killer application for NDGPS, as it would save the railroad industry billions per year and justify the cost of installing and maintaining the NDGPS. The DOT says the PTC doesn’t need NDGPS any longer.

Two significant developments have reduced the need for NDGPS since the program began. The first is that autonomous (standalone) GPS accuracy is very good these days, on the order of a few meters. The second is the maturation of the Federal Aviation Administration’s Wide Area Augmentation System (WAAS).

RITA to the Rescue. Last summer, with no FY07 budget for NDGPS, the scrambling began. The FRA washed its hands of NDGPS so the DOT transferred the program to a little-known agency called Research and Innovative Technology Administration (RITA). At the eleventh hour, RITA scraped up $5 million for NDGPS for FY07 — enough to operate and maintain the system until October 2008. $400,000 of that is allocated for “needs assessment.” In other words, they need to understand who is still using NDGPS and determine if the usage justifies future funding.

The USCG (39 sites), USACE (9 sites), and DOT (38 sites) fund the 86 stations. USCG has said it would take over 12 of the DOT-funded sites if DOT decides not to fund the program. So the debate only involves about a third of the U.S. land mass. The USCG and USACE sites are not in jeopardy, as their requirements are considered safety-of-life for maritime navigation.

Is there is a significant enough user base in the areas above to justify the roughly $7 million a year it takes to operate and maintain them? If there are only 1,000 users in those regions who use it regularly, that’s $7,000 per year, per user. That scenario doesn’t make sense. And it doesn’t even consider the cost of complete system build-out. Even at 10,000 users (a very unrealistic number), that’s still a cost of $700 per year, per user to the taxpayer.

Who still uses NDGPS, anyway? That’s the magic question, and the DOT doesn’t know the answer. Presumably, determining that is part of the needs assessment, to be

finalized in September 2007. I’ve heard speculators talk about agriculture being a big NDGPS user. While this might have been true five years ago, WAAS now dominates the ag market. Even CSI (now Hemisphere GPS), the largest producer of after-market “Coast Guard” beacon receivers and the leading GPS supplier to the ag market, has shifted its focus from NDGPS receivers to high-performance WAAS receivers.

The forest products industry comprises some big users of GPS, but they’ve been post-processing for years, and some have even stopped doing that because autonomous GPS is sometimes good enough.

What’s left is a fragmented group of utilities, federal/state/local government, engineering, surveyors, universities. and various -ologists. Honestly, as much traveling, conference attending, speaking engagements, and training as I do, I can’t recall the last person who told me they use NDGPS. That’s the fundamental problem.

This article is tagged with , and posted in GNSS, Latest News, Transportation