Regional PPP-RTK with CDMA+FDMA data at undifferenced and uncombined level

doi:10.11947/j.AGCS.2023.20210422

Abstract

Abstract: To conform to the trend of multi-frequency and multi-GNSS, PPP-RTK is gradually transforming its data processing mode from the ionosphere-free method to the undifferenced and uncombined one. Existing studies on undifferenced and uncombined PPP-RTK mainly focus on the code division multiple access (CDMA) systems, whereas conducting frequency division multiple access (FDMA) PPP-RTK is challenging due to the effects of inter-frequency bias. This work proposes a regional PPP-RTK model which is capable of processing multi-frequency CDMA and FDMA data at undifferenced and uncombined level. The model adopts the recently proposed integer estimability theory to realize FDMA PPP-RTK in a network of homogeneous receivers, thereby ensuring the rigor of ambiguity resolution. We carry out experiments by collecting GPS, BDS, Galileo, GLONASS data with a sampling rate of 30 seconds from the Hong Kong continuously operating reference stations. Results on the network side indicate that, due to the strong correlation between different products, it is not wise to assess the precision of individual product, but necessary to analyze the combined product. After forming the combined product of satellite clock, satellite phase bias, and ionospheric delay, the precision reaches to millimeter level, thus precise enough for user correction. Results on the user side indicate that the time to first fix of GPS, BDS, and Galileo single-system PPP-RTK is 5, 1, and 3 minutes, respectively. Once the ambiguities are successfully fixed, the positioning errors converge to centimeter level. Instantaneous ambiguity resolution is achievable when combining GLONASS and GPS, and the positioning accuracy is improved by, as compared to GPS-only case, 9%, 12%, 14% (on the east, north, up component). Integrating BDS with GPS also achieves instantaneous ambiguity resolution and obtains an accuracy improvement of 29%, 22%, 18% compared to GPS-only case. Combining additionally Galileo observables further improves the accuracy by 12%, 8%, 16%. A slight improvement of 4%, 3%, 8% is obtained by adding GLONASS observables to carry out quad-system PPP-RTK.

Key words: GNSS, frequency division multiple access, PPP-RTK, ambiguity resolution, integer estimability

CLC Number:

P228

HOU Pengyu, ZHANG Baocheng, LIU Teng, ZHA Jiuping. Regional PPP-RTK with CDMA+FDMA data at undifferenced and uncombined level[J]. Acta Geodaetica et Cartographica Sinica, 2023, 52(2): 183-194.

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