SINS/GPS tightly-coupled integrated navigation

The SINS/GPS loose-coupled system has to work in the pure inertial state if less than 4 satellite are available, thus its parameter errors would be unbounded. In view of this problem, a tightly-coupled SINS/GPS integrated navigation scheme is put forward which takes the pseudorange and pseudorange rate of GPS as the observations. The model of tightly-coupled system is set up, and the technology is realized in practical application. The vehicle test results show that: when number of usable navigation satellites is less than four, the latitude and longitude errors of tightly-coupled are both smaller than 100 m and has nothing to do with the navigation time; and when it is equal or more than 4, the latitude error is about 1000 m in half an hour and about 2000 m in an hour. When the usable satellite number is more than four, latitude and longitude errors of tightly-coupled system are both smaller than 10 m, and the altitude error is smaller than 20 m, which are significantly less than those of loose-coupled system.