Department of Homeland Security

U.S. Coast Guard (formerly within the U.S. Department of Transportation [DOT])
Nationwide Differential Global Positioning System (NDGPS) Reference Stations

SRI's Envirotechnical Program, under contract with DOT contractor Parsons Brinkerhoff, prepared a programmatic environment assessment for a joint program to install or reuse low-frequency transmission antenna units as NDGPS reference statements. The proposed deployment and operation of approximately 55 NDGPS reference stations nationwide would provide a ubiquitous GPS correction signal for significantly greater accuracy in GPS positioning. This initiative was led by the Federal Highway Administration in cooperation with the U.S. Coast Guard, Federal Railroad Administration, U.S. Army Corps of Engineers, and National Oceanic and Atmospheric Administration. When fully operational, this system would have far-reaching applications in managing vehicle and railroad traffic separation and providing geographic accuracy for a range of environmental, surveying, and construction applications, among others. Some of the proposed reference stations would consist of antenna equipment previously built for the U.S. Air Force’s abandoned Ground Wave Emergency Network (GWEN) system. In addition to an extensive programmatic environmental evaluation for NDGPS, site-specific investigations of former GWEN properties were conducted to determine whether use of the property would qualify for a categorical exclusion from further environmental review under the National Environmental Policy Act.