Dynamic Monitoring Of Vegetation Coverage In Changsha City Based On Spatiotemporal Fusion Technology

Vegetation coverage,as an important evaluation indicator for ecological restoration,soil erosion,and desertification,has attracted the attention of researchers in recent years.The traditional vegetation coverage measurement method has the disadvantages of high cost,low efficiency and small measurement area.The development of remote sensing technology has made up for the above shortcomings and provided a new way for the calculation of large area vegetation coverage.However,when a single satellite sensor is used for dynamic monitoring of vegetation coverage,its remote sensing image often cannot meet the requirements of high time and high spatial resolution at the same time.In view of the above problems,this thesis takes Changsha,a "cloudy and rainy city",as the research area,and carries out dynamic monitoring research on the vegetation coverage of Changsha from 2000 to 2021 based on multi-source remote sensing spatiotemporal fusion technology.The main work and research contents are as follows:(1)Based on Landsat and MODIS data,the applicability of three spatiotemporal fusion methods,STARFM,ESTARFM and FSDAF,in Changsha was analyzed.The results show that FSDAF method has the highest similarity with the real image in hue.The texture of the ground objects of ESTARFM and FSDAF methods is clear and hierarchical.STARFM method has plaque effect and ESTARFM method has slight distortion.In terms of operation efficiency,STARFM method takes the shortest time,FSDAF method takes the second place,and ESTARFM method takes the most time.In the five band quantitative indexes of Blue,Green,Red,NIR and NDVI,compared with STARFM and ESTARFM methods,FSDAF method can get higher CC,SSIM and PSNR,and smaller RMSE and SAM.(2)Based on the best effective FSDAF method,the vegetation coverage image data of Changsha from 2000 to 2021 was constructed and its spatiotemporal variation characteristics in 22 years were analyzed.The results show that the spatial distribution of vegetation coverage in Changsha is high in the east,low in the middle,and high and low in the west,the average vegetation coverage is 68.98%.In terms of interannual variation,the vegetation coverage fluctuated greatly,and rose slightly in 22 years.In terms of spatial change,the increasing trend of vegetation coverage in Changsha is the highest in the past 22 years,which is mainly distributed in the main urban area in the central part of Changsha,the vast areas in the west and the central-eastern of Changsha.The reduced areas are mainly concentrated in the scope of urban expansion around the main urban area of Changsha and the traffic construction areas between cities.In terms of pattern change,the low vegetation coverage in Changsha was mainly transferred during the 22 years,and the medium-low,medium and medium-high vegetation coverage showed different degrees of degradation,while the high vegetation coverage first decreased and then increased.On the whole,the vegetation coverage in Changsha shows an improvement trend.(3)Based on the PIE-SDK platform,combined with C# and Python language,a vegetation coverage monitoring system based on spatiotemporal fusion technology was developed to realize the preprocessing of remote sensing images,integration and precision analysis of spatial and temporal fusion algorithm,extraction and change analysis of vegetation coverage,and verify the stability and effectiveness of the system through testing.The system integrates spatiotemporal fusion and vegetation coverage monitoring well,and better applies the research results to the actual production.(4)Based on the climate,topography and socio-economic datas of Changsha,the influencing factors of vegetation coverage change were analyzed.The results show that in terms of climate factors,vegetation coverage in Changsha has a positive correlation with temperature and precipitation,and temperature is the main factor affecting vegetation coverage in climate factors.In terms of topographic factors,the vegetation coverage shows an increasing trend with the increase of altitude and slope,and the slope direction has little impact on the vegetation coverage.With the rapid development of economy,human activities also have an important impact on the change of vegetation coverage.In the comprehensive impact of multiple factors,elevation has the highest impact on the vegetation coverage in Changsha,and when each influencing factor interacts with each other,it will increase the impact on the evolution of vegetation coverage,the interaction types are mainly two factors enhancement and nonlinear enhancement.There are 45 pictures,20 tables and 102 references.