| With the development and improvement of the Global Navigation Satellite System(GNSS),in addition to the traditional navigation,positioning and timing functions,its reflected signals can also be received and utilized,thus becoming a new type of remote sensing.In this context,the principle and process of GNSS-MR(GNSS Multipath Reflectometry)sea level change monitoring technology based on Signal-to-Noise Ratio(SNR)observations are introduced in this paper.Sea surface multipath effect and its influence on GNSS precise positioning are analyzed.It is proposed to use multi-mode multi-frequency SNR data for joint monitoring of tidal level changes to improve the temporal resolution and accuracy of tidal level monitoring.Focusing on the above research contents,the research contents and results of this paper mainly include the following points:1.The characteristics of SNR observations are introduced.The correspondence between low elevation angle range and multipath effect is analyzed.The principle of GNSS station surface environmental parameter monitoring which is based on SNR observation is described.Furthermore,the principle and process of sea level monitoring using GNSS-MR technology are given.The GNSS station observation data and the tidal level data of the tide station are selected for analysis,and the feasibility and effectiveness of GNSS-MR for monitoring the tidal level change are verified.The results show that GNSS-MR technology can accurately obtain sea level values and monitor sea level changes.2.The coastal GNSS station was selected to study and analyze the multi-path effect characteristics and time series characteristics of the sea surface.The impact of sea surface multipath effects on the precise positioning of GNSS was evaluated by designing experimental protocols.The results show that when the elevation angle is between 10° and 15°,the multi-path effect of the sea surface has no obvious influence on the precise positioning of the station.Coastal GNSS stations can be used in both crustal deformation monitoring,sea level change monitoring and other fields to achieve a multi-purpose function.3.The GNSS station multi-mode multi-frequency SNR data is used for joint monitoring of tidal level changes to improve the accuracy and low time resolution of single-system GNSS-MR technology.Experiments with measured data show that the joint monitoring of tidal level changes with multi-mode multi-frequency SNR can greatly improve the time resolution.At the same time,the accuracy of tidal level monitoring is guaranteed.4.Based on MATLAB software,the software design and implementation of tidal level monitoring using GNSS-MR technology is carried out.The software function module is tested by the measured GNSS observation data.The results show that the implementation of GNSS-MR sea level monitoring software reduces the heavy data processing in the tidal level change monitoring process and effectively improves the tidal level change monitoring efficiency. |
