A study of INS/CDGPS integration with a scalar adaptive filter

This paper presents an INS/CDGPS integration system providing a stable navigation solution under the condition of frequent blockage of the GPS signals. In the CDGPS, the Hatch filter is widely used by combining code and carrier phase measurement. Thus the accuracy of the filter depends on both that of measurements. However, the averaged code accuracy of the Hatch filter cannot reach the low noise level under the urban-canyon environment where the cycle slip frequently occurs. In this paper, an algorithm using a scalar adaptive filter as a pre-filter of the Hatch filter is proposed to calculate the more accurate solution for the INS/CDGPS integration system. Using the real test data of INS/CDGPS, it is shown that the presented result is as good as the result provided in commercial software with real data.