Absolute Positioning Using the Global Positioning System.

摘要

The Global Positioning System (GPS) has become a useful tool in providing relative survey control. The relative positioning accuracies of the GPS are commonly on the order of 1-10 parts per million (ppm). The drawback with relative positioning is the user must have one or more known control stations. In areas like the Continental United States (CONUS), survey control is abundant. However, in the near future, the Corps of Engineers may be asked to provide engineering and mapping support to countries which have limited or nonexistent geodetic control networks. In these areas, the engineer and surveyor will not have known control to initiate a survey. In this case, the surveyor will be required to establish one or more absolute control points. To achieve absolute positional accuracies of 1-3 meters, the user must occupy the unknown station for 4-6 hours. The data reduction would take place at the Defense Mapping Agency (DMA), Washington, DC, and the user could wait for several weeks to receive the adjusted coordinates. Recently, USAETL adapted the absolute positioning program created by DMA to run on a standard IBM XT or compatible personal computer. After a few hours of data collection, the absolute positioning program CORPSABS allows the user to estimate the three dimensional position within a matter of minutes. The positioning results can be refined when the DMA precise ephemerides become available. This paper quantifies the accuracy of absolute GPS positioning and evaluates its application to the civilian sectors of the Corps of Engineers. Global positioning system, CORPSABS, Absolute positioning.