U.S. Department of Transportation
Federal Highway Administration
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Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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Publication Number: FHWA-RD-03-039
High Accuracy-Nationwide Differential Global Positioning System Program Fact Sheet
The High Accuracy-Nationwide Differential Global Positioning System (HA-NDGPS) program provides the capability to broadcast corrections to the Global Positioning System (GPS) over long ranges to achieve a better than 10 centimeter (cm) (95 percent) accuracy throughout the coverage area. HA-NDGPS is currently undergoing a research and development phase. The signal is available for test purposes from Hagerstown, MD, and soon Hawk Run, PA. Application of this technology will provide advanced safety features for transportation, including lane departure warning, intersection collision warnings, and railroad track defect alerts. It also could be used for economic enhancements such as precision container tracking and automated highway lane striping.
Currently, the GPS service offers a 4- to 20-meter (m) navigational accuracy. For many land transportation uses, this accuracy is insufficient. The Nationwide Differential Global Positioning System (NDGPS) offers a 1- to 3-m radio-navigational service that meets the needs of many more transportation users.
HA NDGPS Description
Because greater precision is needed to support many of the safety enhancements envisioned for the future, the U.S. Department of Transportation, in conjunction with the Interagency GPS Executive Board, is supporting the development of HA-NDGPS to provide 10 cm horizontal and 20 cm vertical (95 percent) corrections to users. HA-NDGPS uses the infrastructure employed by the NDGPS service to broadcast these corrections. The addition of a diplexer and transmitter allow the existing infrastructure to broadcast the additional signal, keeping implementation costs very low. Additionally, the signal will be monitored to ensure it is providing the accuracy needed to meet safety-of-life applications.
FHWA currently is involved in the testing and implementation of this proposed system. Additional information will be available at https://www.fhwa.dot.gov/research/tfhrc/its/ndgps/index.htm.
A test version of the HA-NDGPS is being made available at the Hagerstown, MD, and Hawk Run, PA, NDGPS facilities. The signal will be available for approximately 1 year and can be received by anyone with appropriate receiver equipment operating within approximately 322 kilometers of the Hagerstown and Hawk Run facilities. Application developers are encouraged to learn more about this testing and to determine the ability of the technology to meet safety application requirements.
The HA-NDGPS program is implemented through funding made available from the Interagency GPS Executive Board and jointly with the U.S. Department of Transportation’s Federal Highway Administration; the Department of Homeland Security’s U.S. Coast Guard; and the U.S. Department of Commerce’s National Geodetic Survey and Forecast Systems Laboratory.
Publication No. FHWA-RD-03-039