Sunil B. Bisnath

Initial results from a long baseline, kinematic, differential GPS carrier phase experiment in a marine environment

The University of Southern Mississippi (USM) and the University of New Brunswick (UNB) have collaborated to devise and carry out a long-term experiment in precise GPS positioning over long distances in a marine environment. A pair of GPS reference stations have been deployed on either side of the Bay of Fundy in Canada, at the terminals of an approximately 75 km ferry route. A geodetic receiver has been installed on the ferry. Surface meteorological equipment has also been collocated with the three receivers. The primary goal of the study, over the course of one year of data collection from the daily ferry runs, realizing that the differential troposphere is a major limiting factor in marine positioning, is to attempt to advance positioning results by means of improved differential tropospheric modeling. The results presented in the paper include a full description of the experiment, and descriptions of the GPS and meteorological data collected, as well as the software used in the processing. Initial PPK data processing results are presented illustrating positioning accuracy versus baseline length. And results from tests using various tropospheric delay values are presented.

CHAMP Orbit Determination with GPS Phase­ Connected Precise Point Positioning

A completely geometric approach for precise orbit determination (POD) of low earth orbiters (LEOs) is presented, which does not rely on dynamic models, but only data from a GPS receiver onboard a LEO and the International GPS Service (IGS) GPS orbit and clock products. Initial processing of CHAMP receiver data indicated measurement anomalies requiring additional pre-processing. The exising of outliers becomes a significant concern in the processing, given that this results in significant gaps in datasets. Intermediate processing results indicate that orbit comparison precision approaching 30 cm r.m.s. in each position component is attainable. However, these results are severely impacted by the near ubiquitous data gaps in the preprocessed measurements. However, initial analysis of recent data indicates quality datasets capable of providing near-decimetrelevel precision.