Abstract
Two estimation methods using a dual GNSS (Global Navigation Satellite System) receiver system are proposed. The dual-frequency combination method combines the carrier phase observations of dual-frequency signals, whereas the single-frequency combination method combines the pseudorange and carrier phase observations of a single-frequency signal, both of which are geometry-free strictly combination and free of the effect of ionospheric delay. Theoretical models are established in the offline phase to describe the relationship between the spectral peak frequency of the combined sequence and the antenna height. A field experiment was conducted recently and the data processing results show that the root mean squared error (RMSE) of the dual-frequency combination method is 5.04 cm with GPS signals and 6.26 cm with BDS signals, which are slightly greater than the RMSE of 4.16 cm produced by the single-frequency combination method of L1 band with GPS signals. The results also demonstrate that the proposed two combination methods and the SNR method achieve similar performance. A dual receiver system enables the better use of GNSS signal carrier phase observations for snow depth estimation, achieving increased data utilization.
Highlights
Snow is one of the most widely geographically distributed substances on Earth’s surface and has one of the most significant seasonal and inter-annual variabilities in the cryosphere [1]
Global navigation satellite system (GNSS) remote sensing consists of two different technologies; one is GNSS radio occultation (GNSS-RO) and the other is GNSS reflectometry (GNSS-R)
In the measurement of snow depth, the pseudorange and carrier phase data are collected from the receiver, the data are combined according SFC or DFC to produce the error time series, the Lomb Scargle spectrum analysis is performed to obtain the spectral peak frequency of the time series, the antenna height relative to the snow surface is directly calculated by Equation (15), and the snow depth estimate is generated
Summary
Snow is one of the most widely geographically distributed substances on Earth’s surface and has one of the most significant seasonal and inter-annual variabilities in the cryosphere [1] It plays a very important role in the adjustment of the global climate and hydrological cycle [2,3]. Ozeki and Heki proposed to combine the dual-frequency phase observation of the L1 carrier and the L2 carrier of GPS (Global Positioning System) signals to estimate snow depth, which is called the L4 method [22]. The combinations eliminate or greatly weaken the effects of satellite ephemeris errors and satellite clock errors This is because the two methods proposed in this paper use two differences, the first one is the difference between pseudorange observations and carrier phase observations of the same receiver, which can decrease the satellite clock error and ephemeris error
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