Research On The Glacier Elevation Change Monitoring Based On Domestic Stereo Mapping Satellites

The "third pole" with the Qinghai-Tibet Plateau as the core is the area with the largest ice and snow reserves except for the Antarctic and Arctic.It is known as the "water tower of Asia".The glaciers on the Qinghai-Tibet Plateau are of great strategic significance as the most important freshwater reserve resources.Therefore,studying the surface elevation changes of glaciers in the Qinghai-Tibet Plateau can provide theoretical and data support for the assessment of freshwater resources and the analysis of climate change.The open source DEM data set has the shortcomings of low accuracy and limited data years,which is difficult to meet the needs of short-term glacier change monitoring.Therefore,this paper takes the Purogangri Glacier,the "third polar point",as the research area,uses the domestic ZY-3 stereo image combined with GF-7 laser altimetry standard product to establish high-precision DEM in different periods,and applies it to the monitoring of glacier elevation change.The main work of this paper is as follows:(1)High precision DEM production.The selected GF-7 laser control points are used to assist the regional network adjustment of ZY-3 stereo images and optimize the stereo image orientation parameters.DEM is produced based on stereo images with improved accuracy.The elevation accuracy of ZY-3 DEM in glacier area is better than 4m.Compared with the elevation accuracy before laser optimization,the elevation accuracy of DEM is improved by more than2 m.(2)Quality comparison with open source data sets(SRTM,AW3D30,Tan DEM,HMA).In terms of texture definition,ZY-3 DEM and HMA belong to the high spatial resolution terrain reference data.The detailed description of the glacier end has an absolute advantage over the medium spatial resolution data set.The detailed texture is clear and can reflect the real terrain condition of the glacier end.In terms of elevation accuracy,the accuracy is HMA,ZY-3 DEM,AW3D30,SRTM and Tan DEM from high to low.The HMA data source is a sub-meter-level resolution satellite,so it has high elevation accuracy and the ability to describe terrain details,but its data coverage is sparse and there are many holes.The ZY-3 satellite has launched three satellites in succession,which can achieve full coverage of the Qinghai-Tibet Plateau area and is rich in data.To sum up,ZY-3 DEM has the advantages of high accuracy,strong ability to describe terrain and rich data volume compared with open source terrain reference data set.(3)Multi-temporal DEM difference method is used to monitor the change of glacier elevation.Evaluate the accuracy consistency of ZY-3 DEM data in two phases to ensure the reliability of monitoring results.The monitoring results show that the glaciers have been in a state of thinning in the past six years,showing that the melting amount of glaciers gradually decreases with the increase of altitude,and gradually tends to be stable and under zero.When analyzing the elevation change of each ice tongue,it is found that two swell-type glaciers are in the transition period,with the maximum melting amount of 22.1m and the maximum accumulation amount of 66.9m in each interval.The swell-type glacier is a disaster-prone area and should attract people’s attention.In this study,Puruogangri Glacier is taken as the experimental area.Based on ZY-3 stereo pair and GF-7 laser altimetry data,the establishment of high-precision DEM in the glacier area is realized,which provides a new idea for glacier monitoring.Compared with the open-source DEM data,the DEM produced by domestic stereo mapping satellite has the advantages of self control,stable data source and high accuracy.It can provide reliable data support for glacier research on the Qinghai Tibet Plateau,better serve the national development strategy,and effectively protect the third pole ecology.There are 45 figures,16tables and 104 references in this paper.