G.P.S. Applications in Support of the Georgia Environmental Protection Division's Drinking Water Program

Abstract

Resource grade GPS receivers are being used to determine the positional indices for wells and associated potential pollution sources for public wells in Georgia. This study was conducted to evaluate the accuracy and precision of the applied technology and techniques. Sixty differentially- corrected GPS positions were calculated at a 1st order monument located 257 miles from the GPS Base Station. The horizontal mean radial error for these tests was 7.8 ft. The RMSE was 9.6 ft. and 98% of all calculated positions fell within 19.2 ft. of the true positions. Elevation errors were about 1.5 times greater than those for horizontal positions. These tests were conducted under ideal conditions. Traditional surveying is used to determine bearing and distances between wells and associated potential pollution sources. A bearing/distance is then shot to a GPS location that is clear of obstruction. The Geographic Calculator is then used to translate distances and bearing from station to station for positional indices. This technique maximizes the accuracy of both horizontal and vertical positional data.