The analysis on geometry dilution of precision for multi-GNSS

The geometry dilution of precision (GDOP) has been widely used as an accuracy metric for GNSS. The conventional GDOP, mainly investigated for single GNSS, is not valid for multi-GNSS because of the system time offset among GNSSs. This paper performs a GDOP analysis for two scenarios where the system time offset is resolved respectively at system level and at user level in presence of any number of GNSSs. The closed-form solutions for the minimum of GDOPs in both scenarios are derived firstly as a function of the number of the satellites in different GNSSs. The minimum of GDOP can be a reference to assess the quality of the employed satellite. Then we propose a new DOP parameter, position and time dilution of precision (PTDOP), for mathematical comparison between the two system time offset determination methods. The comparison of the analytical and simulations between the both scenarios shows that the system level method slightly outperforms the user level method for the receiver.