The performance of GPS Standard Positioning Service without selective availability

The accuracy of the Standard Positioning Service of GPS has greatly improve d after the termination of Selective Availability. Based on GPS observation s from permanent GPS-fixed stations, the actual accuracy of GPS without SA is analyzed. For Station NCTU, the local geodetic coordinates are computed with the C/A code pseudo-ranges, and then transformed into a local grid sys tem with Trans-Mercator projection. From 77984 single epoch observations co llected in twenty-nine days, the 95% accuracy is found to be DeltaE : 17.65 44m, DeltaN : 11.8236, DeltaH : 31.8018m. For five selected UNAVCO stations , the axes of error ellipsoid are computed.