BDS and GPS stand-alone and integrated attitude dilution of precision definition and comparison

Attitude Dilution of Precision (ADOP) is an important indicator that reflects the relationship between attitude errors and noise in carrier phase observations for Global Navigation Satellite System (GNSS) attitude determination. Several definitions of the ADOP have been put forward by some scholars so far. However, there is no widely accepted standard ADOP definition currently. Therefore, the most exact ADOP definition need to be selected to compare the attitude determination performance of BDS and GPS stand-alone and integrated system. In this paper, three representative ADOP definitions are studied. Theoretical analysis and data simulation show that the ADOP definition proposed by Gomez is the best among these three definitions. After that, the ADOP for BDS and GPS integrated attitude determination is defined based on the ADOP-Gomez definition. BDS and GPS stand-alone and integrated ADOP are calculated in a three-antenna static attitude determination experiment. The experimental results demonstrate that the ADOP for GPS stand-alone system is on the whole lower than BDS stand-alone system, which means the geometry strength of GPS for attitude determination is stronger than BDS. Even so, the ADOP for BDS is nearly close to GPS in the condition that the visible satellite numbers of BDS and GPS are almost the same. It is also concluded that the ADOP for BDS and GPS integrated system significantly decreases compared with their stand-alone system.