On-the-Fly Ambiguity Resolution Based on Null Space Constraints of GPS Double-Differential Carrier Phase

This paper proposed an efficient on-the-fly ambiguity resolution algorithm using non-dedicated GPS receivers. It transforms the double-differential carrier observation equation using null space transformation so that it need not to resolve real-time three-dimensional position parameters. After then short baseline length determine the ambiguity search space by the principle of GPS interferometer. Three independent ambiguities are selected by XDOP to reduce the ambiguity candidates, along the baseline length constraint. The validation of correct ambiguities adopts several statistical conditions aided by a low-precision heading reference. Trials were done by Garmin25 LP receivers to resolve the heading and pitch. It shows that the method can reliably on-the-fly resolve the ambiguity. The heading accuracy of the GPS attitude system can reach 1°.