Local geoid determination using the Global Positioning System

Abstract

A local geoid model to predict the geoid heights in the vicinity of Monterey Bay, California, was developed to use Global Positioning System (GPS) differential positions and known Mean Sea Level (MSL) with the method of collocation. The local geoid models were based on Rapp's 360 degree x 360 order global geoid model determined from gravity measurements. Control data were adjusted by least squares to solve for the parameters in the local geoid model. Also studied were factors that affected the GPS-measured ellipsoid height differences. These included (1) comparing GPS differencing solutions, (2) standard error of GPS observations, (3) corrections for surface meteorological values, and (4) observation durations for GPS. The data used in this research were taken from GPS measurements on the campus of the Naval Postgraduate School (NPS), an area about 100 m x 630 m and in an area approximately 15 km x 33 km near Monterey, California. The time period was from February 5, 1988, to May 12, 1988. The accuracy of the predicted geoid heights is ± 2 cm if a six-parameter model is used for the large area, and ± 2 to 10 mm if a five-parameter model is used for the NPS campus.