GNSS undifferenced and uncombined data processing and PPP-RTK high-precision positioning

doi:10.11947/j.AGCS.2022.20220134

Abstract

Abstract: This work discusses the origins, features, and applications of GNSS differenced and combined data processing methods. After pointing out some limits of the differenced and combined methods under the background of multi-frequency and multi-GNSS, we summarize the advantages of the undifferenced and uncombined data processing method and introduce the rank-deficiency elimination strategy that is used to construct full-rank undifferenced and uncombined models. Based on this strategy, we systematically formulate a class of undifferenced and uncombined integer ambiguity resolution-enabled precise point positioning (PPP-RTK) functional models, including code-plus-phase and phase-only categories. Both categories impose different constraints on ionospheric delays and yield three variants, including ionosphere-weighted, ionosphere-float, and ionosphere-fixed variants. All variants consider both code and frequency division multiple access signals. Finally, we evaluate the undifferenced and uncombined PPP-RTK performance by conducting boat-borne, airborne, and tractor-borne positioning experiments. Results show that, for three cases, the time to first fix is less than 10 s, the ambiguity success rate is higher than 96%, the horizontal positioning accuracy is better than 2 cm, and the vertical positioning accuracy is better than 5 cm. For Galileo+GPS+BDS triple-system tractor-borne positioning, the performance of phase-only PPP-RTK is comparable to that of code-plus-phase PPP-RTK. Compared to Galileo+GPS dual-system positioning, triple-system positioning decreases the time to first fix from several hundreds of seconds to several seconds, improves the ambiguity success rate from approximately 85% to better than 99%, and improves the positioning accuracy by approximately 30%.

Key words: GNSS, undifferenced and uncombined data, data processing, rank-deficiency elimination, PPP-RTK, functional model

CLC Number:

P228

YUAN Yunbin, HOU Pengyu, ZHANG Baocheng. GNSS undifferenced and uncombined data processing and PPP-RTK high-precision positioning[J]. Acta Geodaetica et Cartographica Sinica, 2022, 51(7): 1225-1238.

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