Analysis of inter-frequency bias in multi-mode multi-frequency GNSS-IR water level retrieval and correction method

doi:10.11947/j.AGCS.2022.20210461

Abstract

Abstract: Accurate water level monitoring is very important for water resources regulation, flood monitoring, and climate and meteorological research. In recent years, with the continuous development of GNSS, one technique named GNSS-interferometry reflectometry (GNSS-IR) water level retrieval has been proposed. Currently, three types of errors—height variation error, elevation bending error and tropospheric delay error have been discovered, and related correction methods have also been proposed. After analysis of the multi-mode and multi-frequency retrievals of four GNSS stations (HKQT, SW50, SW51 and SW52), this paper found that there is also an obvious inter-frequency bias in retrievals in addition to the three types of errors. Previous research has few studies on GNSS-IR inter-frequency bias, and there is no consensus that it is classified as a GNSS-IR error source. In order to further dig out the characteristics of the inter-frequency bias and deepen the understanding of this error, this paper calculated the reflector height (RH) of different signals, and found that there were deviations between the RH values of different frequency signals. Comparing these deviations with the corresponding wavelengths, we found that these deviations have a significant linear relationship with the signal wavelengths (correlation coefficient>95%). The magnitude of these deviations were in a decimeter level, which showed system characteristics of obvious inter-frequency bias. Based on the characteristics of the inter-frequency bias, this paper proposed an error correction method. The results showed that root mean squared errors (RMSEs) of the correction retrievals with consideration of the inter-frequency deviation were 1.5 to 12 cm higher than these without consideration. And the accuracy of the corrected combined retrievals was 30%~80% higher than the retrievals of the uncorrected individual signals. The improvement of accuracy benefits from the large amount of redundant data provided by the multi-mode and multi-frequency signals and the correct handling of various errors including systematic errors, gross errors and random errors.

Key words: GNSS-IR, water level retrieval, inter-frequency bias, error correction

CLC Number:

P227

WANG Xiaolei, HE Xiufeng, SONG Minfeng, CHEN Shu, NIU Zijin. Analysis of inter-frequency bias in multi-mode multi-frequency GNSS-IR water level retrieval and correction method[J]. Acta Geodaetica et Cartographica Sinica, 2022, 51(11): 2328-2338.

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