Flight tests of GPS/GLONASS precise positioning versus dual frequency KGPS profile

The benefits of combined use of the GLONASS and GPS navigation satellite constellations have become obvious for applications such as open-cast mining operations and highly dynamic vehicles such as spaceplanes. Moreover, using GLONASS satellites in addition to GPS is useful for long baseline applications since it increases the numbers of satellites in common view. Japan’s National Aerospace Laboratory (NAL) has been conducting feasibility studies using combined GPS/GLONASS positioning for spaceplane landing systems and the precise navigation of stratospheric airships. This paper presents the results of the first Japanese kinematic GPS/GLONASS flight test. In the test, the difference in estimated position between dual frequency GPS and single frequency GPS/GLONASS systems was found to be within a few centimeters, indicating that GLONASS carrier phase ambiguities were correctly resolved. To demonstrate the benefits of combining GLONASS with GPS navigation, an on-the-fly (OTF) test of instantaneous ambiguity resolution with a 30 degree cutoff angle was performed. The OTF performance of the combined GPS/GLONASS system was found to be similar to that of a GPS system with a cutoff angle of 10 degrees, showing that augmentation of GPS with GLONASS will be useful for highly dynamic vehicle applications.