Geostationary satellite coverage for surface applications of differential global positioning system

The coverage issues surrounding the use of geostationary satellites for surface applications using Differential Global Positioning System (DGPS) data are examined. The Federal Aviation Administration's Wide Area Augmentation System plan to use geostationary satellites to provide differential corrections for aviation users is presented. Impediments to coverage include man-made structures, irregular terrain (i.e., mountains), and attenuation or signal fading due to tree canopy. Each of the impediments is examined and an assessment is made of their effects on coverage. Various user groups require ubiquitous coverage, and a geostationary satellite broadcast of corrections does not provide this. Large gaps will exist in rural and urban areas, and signal fading due to tree canopy will be significant over much of the country. Alternative communication techniques, such as the U.S. Coast Guard Low Frequency Radiobeacon DGPS service, should be used to meet surface user requirements.