NCHRP Supports Advances in Differential GPS Satellite Surveying

This Digest is a status report on National Cooperative Highway Research Program (NCHRP) Project 20-23, Kinematic Differential GPS Satellite Surveying. Although the Global Positioning System (GPS) is a satellite system being developed by the Department of Defense, some civilian applications are allowed. Presently, 15 satellites providing positioning information are in orbit. An 18-satellite constellation providing 24-hour coverage is expected to be fully operational in late 1993. This research has resulted in a technique by which highway engineers and surveyors may rapidly obtain precise positions necessary to maintain geodetic control. The technique uses measurements of the GPS, commercially available GPS receivers, and personal computers for data processing. Users of this technique need to occupy each point to be surveyed for only one or two minutes, thus providing an efficient means to quickly and precisely survey a large number of points. Horizontal accuracies of one centimeter and vertical accuracies of three centimeters have been demonstrated. The software has been written to run on most available personal computers and can be operated with no special skills required. NCHRP Project 20-23 is essentially completed; however, the finalized research reports are still pending.