Research On Remote Sensing Monitoring Method Of Typical Water Level

Compared with traditional water level monitoring methods,satellite altimetry technology can monitor the water level of typical water bodies on a large scale,all day,and all weather,and has become an important method for global ocean and inland water level monitoring.Due to the unique advantages of satellite altimetry technology,it can provide great help to remote areas without water level data.At present,the altitude measurement satellite radar altimeter can measure the instantaneous sea surface with a high accuracy of 5cm in the open sea,which has greatly promoted the development of geodesy,geophysics,oceanographic research and other fields.However,because satellite altimetry technology was originally designed to obtain ocean-related information,different areas of the non-wide ocean are affected by factors such as topography and surrounding environment,resulting in a decrease in the accuracy of satellite measurements.Based on the research results at home and abroad,this paper uses waveform re-tracking to correct the "pollution" of satellite altimetry waveforms in the middle reaches of the Yangtze River,Hongze Lake and Beibu Gulf caused by the surrounding environment of the ground features,and adopts The data quality screening method further improves the accuracy of the altimetry satellite data.It is expected to provide technical research support for areas without hydrological data to fill in data gaps.The main research contents and conclusions of this paper are as follows:(1)Select the SGDR data of Jason-2 and Jason-3 satellites from July 2008 to December 2019 to analyze the satellite altimetry echo waveform data in the offshore area of ??Beibu Gulf,Hongze Lake and the middle reaches of the Yangtze River.For the echo waveform in the middle reaches of the Yangtze River,the rising edge of the echo waveform is more obvious in the wet season,and the rising edge of the echo waveform in the dry season is very low,which cannot be distinguished visually,resulting in re-tracking of the waveform.The algorithm cannot perform waveform re-tracking;the echo waveforms in the Hongze Lake area are sorted from low to high latitude,showing that the rising edge of the echo waveform at low and high latitudes is more obvious and the thermal noise is low,and the echo waveform at mid-latitudes is before rising.The edge is low,and the trailing edge is more complicated.In the offshore area of ??the Beibu Gulf,the echo waveform is consistent with the echo waveform of the broad ocean,both of which exhibit low noise and have the characteristics of an obvious rising front edge of the waveform.(2)On the basis of understanding and analyzing typical waveform re-tracking algorithms,an adaptive waveform re-tracking algorithm(AMWRT)based on the main peak is constructed.The main peak is searched to reduce the influence of thermal noise of complex waveforms,combined with typical waveform re-tracking.The tracking algorithm has been well applied in different areas of non-wide seas.1(3)Different waveform re-tracking algorithms re-corrected the satellite-to-water surface ranging value(Range),added various error corrections to obtain the instantaneous water level and sea level height of the altimetry points in each period,combined with the data quality level screening method to filter the results Calculate the average value of the data,and finally obtain the satellite instantaneous water level and sea level anomalies in a certain period of time.Analyze the correlation between the satellite water level,sea level anomaly and the measured data of the water level station.Different waveform re-tracking algorithms are not applicable in a certain area,and satellite water levels in the middle reaches of the Yangtze River,Hongze Lake,and Beibu Gulf offshore areas.,The sea-level height anomaly tends to be consistent with the change trend of the measured data,but there is still a difference in the accuracy of the data.(4)This paper uses the measured data from hydrological stations to carry out precision inspection and analysis on the calculation results of SGDR data,and compares the application of different waveform re-tracking algorithms in different research areas.The details are as follows:(1)In the study area of ??the middle reaches of the Yangtze River,the AMWRT algorithm performs better than other re-tracking algorithms,with MAE of 0.55 m and RMSE of 0.72 m.Compared with the 50% threshold level threshold algorithm that performs better in the classic re-tracking algorithm,the MAE is 0.84 m and the RMSE is 1.04 m,which improves the accuracy by 30%.(2)In the Hongze Lake research area,the AMWRT algorithm performs better than other re-tracking algorithms,with a MAE of 0.09 m and an RMSE of 0.12 m.Compared with the 10%threshold level threshold algorithm that performs well in the classic re-tracking algorithm,the MAE is 0.18 m and the RMSE is 0.26 m,which improves the accuracy by 50%.(3)In the offshore area of ??the Beibu Gulf,the performance of the AMWRT algorithm is not much different compared to other re-tracking algorithms.The AMWRT algorithm performs slightly better than other re-tracking algorithms,with MAE of 0.059 m and RMSE of 0.071 m.Compared with the classical re-tracking algorithm,the GDR data comes with a waveform re-tracking algorithm that performs better.The MAE is 0.069 m and the RMSE is 0.091 m,which improves the accuracy by14%.(5)For the satellite altimetry data in the middle reaches of the Yangtze River,Hongze Lake,and offshore areas,the range value(Range)obtained by the AMWRT algorithm is substituted into the water level and sea level anomaly calculation formula,and the establishment and analysis of July 2008 to December 2019 The change rule of the monthly average water level and sea level abnormal change sequence within the monthly time range.(1)The monthly average water level change sequence in the middle reaches of the Yangtze River.The highest water level during the year is from July to August,and the lowest water level is in April of the following year.(2)There is an off-season water level change in Hongze Lake,which has a lot to do with the local water conservancy project.(3)In the offshore area of ??the Beibu Gulf,the sea level change rate from2009 to 2019 is 4.02mm/yr,and the result obtained is not much different from the result of the sea level rise rate of 3.5mm/yr obtained in the 2019 China Sea Level Bulletin.