Dsp-based Gps Kinematic Carrier Phase Differential Technology

Global positioning system (GPS) is a real time, all climate, global navigation and positioning system base on satellites. The relative positioning of GPS is produced and developed for the exaltation of positioning accuracy. On the basis of above, the technique of differential GPS (DGPS) is gradually perfected. This, to a great extent, enhanced the precision of GPS positioning. High precision differential GPS positioning is based on the very precise carrier phase measurements. The key problem of this method is the rapid and correct integer estimation of the GPS double difference ambiguities. The carrier phase differential technique is also called RTK (real time kinematic), which is based on the real time processing the carrier phase of two observation stations. While the RTK system is working, the GPS receiver fixed on the base station is taking a continuous observation for all visible GPS satellites, and sending the real time observation data to the moving station over the wireless data link. On the moving station, while the GPS receiver is receiving the signal of GPS satellites, it is receiving the observation data from the base station by the radio. Then, according to the carrier phase relative positioning principle, the moving station is real time working out its position, thus, the computing capacity of moving station need to be very strong. With the communication and signal processing technology fast developing, DSP is widely used, we can use the carrier phase measurements to the real time differential GPS positioning system. The positioning accuracy may reach the centimeter level, and that make it possible to do the dynamic high precision survey in topography and do the high precision satellites navigation in the navigation field.This paper introduces the component s and features of GPS, discusses the working principle and the mathematic model of differential dynamic positioning technology with GPS carrier phase in real time, and simulating its performance of positioning, describes the basic idea of integer ambiguity resolution, analyses the methods of ambiguity resolution, especially the LAMBDA (least-squares AMBiguity Decorrelation Adjustment) method. Based on The float ambiguities and their variance-covariance matrix, LAMBDA firstly decorrelates the ambiguities, and secondly searches discretely over the ambiguity search ellipsoid, therefore obtain the integer least-squares estimate for the ambiguities, the fixed solution can be computed.After the integer estimation have been carried out very fast and efficiently, we can get the baseline fix solution to achieve the real time, dynamic and precise positioning. At last, we put the main part of LAMBDA algorithm on DSP platform in C codes. With the test data, we validates the LAMBDA algorithm can be used on DSP platform and working well, so it can be used in carrier phase real time differential GPS positioning system, to achieve the precise positioning.