Extraction Of Glacier Motion Field In Kangchenjunga Area Based On GF-3 SAR Images

The mobility is one of the main characteristics of glaciers.It is of great significance to monitor the change of glacier surface velocity for the study of glacier material balance and glacier disaster.At home and abroad,the research on glacier velocity using satellite SAR images mostly uses foreign satellite SAR images.Since the launch of GF-3,the first C-band multipolar SAR satellite independently developed by China,there have been a lot of SAR data,but the research on glacier velocity monitoring is less.In order to quickly apply GF-3 data to Glacier motion field extraction research and explore the application potential of GF-3 data in remote sensing monitoring of cryosphere,this paper selects Kangchenjunga area in the Middle Himalayas as the research area,and conducts experiments on the imaging quality and glacier displacement monitoring performance of GF-3 image glacier area.Based on GF-3 image,pixel offset-tracking technology(POT)is used,combining with the area Based on the in-depth analysis of regional climate and local glacial topography,the influencing factors of glacial movement are analyzed,and the distribution of large-scale glacial movement(area > 5 km~2)in Kangchenjunga area is analyzed,and the glacial movement field in this area is catalogued.The specific research results and conclusions are as follows:(1)Compared with Sentinel-1A SAR image,the image quality evaluation index of GF-3SAR image is close to that of Sentinel-1A.In terms of spatial resolution and speckle noise level,GF-3 SAR image is better than Sentinel-1A image In SAR image,the radiation resolution of GF-3 image is slightly lower than that of Sentinel-1A image.In addition,because the spatial resolution of GF-3 image is higher than that of Sentinel-1A image,the glacier and ice lake boundary and feature points are clearer,which is conducive to feature point matching and glacier remote sensing monitoring.In general,the quality of GF-3 and Sentinel-1A SAR image in glacier area is similar.(2)Based on the comparison and analysis of the glacier surface velocity measured by the pot technology in the GF-3 and Sentinel-1A SAR images,the migration and tracking results of the glacier accumulation area obtained from the GF-3 image have a large terrain error,and the glacier ablation area is less affected by the terrain.For the monitoring of the movement field in the glacier ablation area,the movement velocity distribution of GF-3 image and Sentinel-1A image along the middle line of the glacier tongue is close,the mean value of the movement velocity is close to the standard deviation,the mean value of the difference is 6.45cm/d,and the standard deviation of the difference is 18.25 cm/d,which cross verifies the applicability of the monitoring of the movement result of the glacier surface based on GF-3image.(3)Based on the GF-3 image,using the pot technology to monitor the largest glacier in Kangchenjunga area,the study found that the flow velocity in the area of the gem glacier snow basin is the largest,about 1 m/d,while in the ablation area,the highest flow velocity reaches30 cm/d,and the flow velocity gradually slows down from the top to the end of the glacier tongue.Based on the data of climate and topography in the study area,it is found that climate change is the main factor controlling the flow speed of Zemu glacier,and the flow velocity in some areas is affected by topography.According to statistics,the residual mean value and standard deviation of the movement rate in the bedrock area are 0.45cm/d and 0.18cm/d,which can be ignored compared with the measured glacial movement rate.This proves the reliability of monitoring the movement rate of the glaciers based on the GF-3 image using the pot technology.(4)The average velocity of 19 glaciers with an area of more than 5 km ~2 in Kangchenjunga area is 5.87 cm/d and the standard deviation is 6.49 cm / d.According to the average velocity of the middle line of the glacier tongue,the glacier movement types can be divided into three types.In type I,the average velocity is more than 10 cm/d,accounting for26% of the total;in type II,the average velocity is between 5-10 cm/d,accounting for 32%;in type III,the average velocity is between 0-5 cm/d,accounting for 42% of the total.There are obvious differences in the distribution of glacier movement between the east and the west in the study area.Taking the north-south ridge line of Kangchenjunga as the boundary,the average movement speed of glacier on the east side is three times of that on the west side.(5)GF-3 images have the advantages of all-time,all-weather,high-resolution,wide range and high cost performance.GF-3 SAR images can be used as a common remote sensing image data source in glacier remote sensing monitoring,providing a new data selection for glacier movement and change monitoring,and playing an important role in Glacier velocity measurement and monitoring.