Delay Difference between Tracking Loops of Different Types or TL with Various Bandwidths of C/A Code in GPS

摘要

In GPS positioning by code timing, the accuracy of the basic stand-alone positioning based only on information broadcast from GPS satellites is approximately 10 m (2 drms). But in GPS utilizing the results of observation by a reference station, the error due to the satellite and the channel can be eliminated, resulting in a positioning accuracy of I m (2 drms) or less. In applications in which high accuracy is required, although not as high as in carrier positioning, but in which the satellite signal is often interrupted, it is effective to use DGPS based on code timing. In DGPS based on code timing, the information acquired by a single reference station can be utilized by many rover stations. Different trackers are used in the reference and rover stations. This paper considers the DLL (delay lock loop) system, which is widely used in code tracking, and the SCELL (sampled code edge locked loop) system, with different characteristics. The differential error between the reference and rover stations which is caused by the difference in the receiver bandwidth, the satellite transmission bandwidth, and the difference in code numbers, is analyzed. It is shown that by widening the tracker bandwidth, the error is made sufficiently small compared to that obtained in ordinary DGPS.