Abstract:

A positioning algorithm based on two satellites was studied in assisted Global positioning system (AGPS) in order to realize positioning efficiently in weak signal to capture satellite and to provide auxiliary data more quickly. The positioning solution was used with Marquardt algorithm in which the step factor is used and adaptively adjusts according to the change of objective function. The errors caused in solving the singular equation groups with GaussNewton algorithm can be removed using this algorithm. The mean positioning bias can be decreased from 703. 24m to 116.63m when there exist two overlapped satellites in two measures or from 108.93m to 32.17m when only one overlapped satellite, but the computation increases only a little.

Key words: navigation principle, assisted Global positioning system, positioning accuracy