Software Developments for Geodetic Positioning with GPS Using TI 4100 Code and Carrier Measurements

Abstract

With phase measurements on the carrier signals of GPS satellites a highly accurate relative geodetic positioning is possible. A main problem concerns the determination of the phase ambiguities. A method which helps to solve this problem using simultaneous P-code and carrier measurements is presented. After a sufficient time of observation pseudoranges with a noise level of a few millimeters are obtained. Software developed at the University of Hannover for the simultaneous detennination of absolute and relative positions using these ranges is described. GPS RECEIVER CODE AND CARRIER MEASUREMENTS A GPS receiver reconstructs either the code, the carrier or both signals of an incoming satellite signal. Measurements are made on these signals through the code and carrier tracking loops. The code tracking loop correlates the incoming code with a code replica generated by the receiver. If maximum correlation is reached the phase of the code replica is a measurement of the received code phase at a time event of the receiver clock. In the carrier tracking loop the relative phase between the reconstructed carrier signal and a reference signal generated by the receiver is measured: where «p