GPS Satellite Surveying — Practical Aspects

Abstract

No satellite-based survey system has gained as much attention and interest as the Global Positioning System (GPS). Establishing precise positions by use of the GPS is rapidly becoming a powerful and economical tool for surveyors. The extensive experience gained at the National Geodetic Survey (NGS), from field tests in March 1983 to operational projects performed later in 1983 and early 1984, has demonstrated that observations of the GPS satellite signals yield very accurate three-dimensional relative position data. Baselines of up to 100 km are routinely measured to accuracies of 1 cm to 5 cm rms. Differential ellipsoid height accuracies at the few centimeter level have been achieved; depending on accuracies of geoidal undulations, useful elevation differences can be computed. This paper focuses on the more mundane activities required to obtain such results. Although GPS satellite surveying employs sophisticated methodology and instrumentation, there are many practical aspects to be considered. These include requirements for ties to existing control, station selection criteria, field procedures, data handling and storage, and processing steps.