| Abstrakt: |
In this paper, the authors present a Global Positioning System (GPS) algorithm for medium accuracy (1-m rms) positioning of ocean buoys. The application addressed in this paper is that of the Fast Pegasus experiments that require the positioning of surface buoys used in collecting subsurface acoustic data for ocean current profiling. The current GPS system designed for the Fast Pegasus experiments requires a land-based single-frequency GPS receiver for differential GPS positioning. In contrast, the technique presented here is designed for the point positioning of a stand-alone single-frequency GPS receiver (which is in motion) and does not require the use of a land-based reference receiver. The precise point positioning algorithm developed here uses postprocessed GPS satellite ephemerides and clock corrections to compute the position of a single GPS receiver. A square root information filter/smoother uses the GPS pseudorange and carrier phase measurements to estimate the position and clock offset of the receiver, 15 ionospheric coefficients from a polynomial ionospheric model, and the carrier phase ambiguities. The two major goals of this algorithm are 1) to provide 1-m (rms) absolute positions and 2) to provide 1-cm s 21 (rms) absolute velocities. In three tests conducted during 1--3 August 1996, the precise point positioning algorithm computes absolute positions with an average bias of 0.396, 0.362, and 20.386 m, in the east, north and vertical directions with average standard deviations of 0.149, 0.216, and 0.484 m, respectively, when compared with carrier phase differential positions. Additionally, the precise point positioning algorithm provides velocity information that has a mean error of 0.01 cm s 21 in all directions with standard deviations of 0.15, 0.19, 0.37 cm s 21 ,in the east, north and vertical directions. Based on the data collected here, the precise point positioning algorithm meets the Fast Pegasus GPS data processing... [ABSTRACT FROM AUTHOR] |
