GNSS Ambiguity Resolution in Kinematic Positioning: Benefits of Satellite Availability and Sampling Rate

摘要

Global positioning system (GPS) precise positioning using carrierrnphase measurements can provide accurate kinematic positioning results,rnwhich have been widely applied to geodesy and geophysics researches.rnAmbiguity resolution (AR) is the procedure to resolve double-differencedrn(DD) integer ambiguity on the phase measurements and is the key tornachieve high-accuracy positioning results. GPS measurement errorsrncritically affect the AR performance. The error sources comprisernmeasurement random noise and systematic errors such as multipath, orbitalrnbiases, and atmospheric delays. In the least-squares process, the use of anrnincreased sampling rate can improve the measurement redundancy andrnmitigate the influence of random noise on the unknown parametersrnincluding ambiguity parameters; however, it cannot effectively reduce therninfluence of systematic errors on the unknown parameters because thernsystematic errors are mostly correlated in time. As a result, the use of anrnincreased sampling rate is not regarded as a crucial means to refine GPS AR.rnCompared with GPS, combined global navigation satellite systems (GNSS)rncan provide enhanced satellite availability, which is a well-known factor forrnAR improvement. Furthermore, combined GNSS can provide betterrnexternal reliability in the least-squares process to reduce the influence ofrnsystematic errors on the unknown parameters. It is therefore expected thatrnan increased sampling rate can lead to further improved combined GNSSrnAR performance. Given the fact that the impact of sampling rate onrncombined GNSS AR has not been assessed before, we develop arngeneralized method to carry out stand-alone GPS and combined GNSSrn(GPS, GLONASS and BDS) AR with different sampling rates ranging fromrn0.05 to 1 Hz. The experimental results show that (1) combined GNSS AR is,rnas expected, more reliable than GPS AR at the same sampling rate by virtuernof the enhanced satellite availability; (2) combined GNSS notably improvesrnthe accuracy of kinematic positioning results in the horizontal and verticalrndirections; (3) using an increased sampling rate effectively further improvesrncombined GNSS AR. As a result, in order to achieve optimized ARrnperformance in kinematic positioning, it is crucial to use combined GNSSrntogether with a high sampling rate.