Extraction Of Paddy Rice Growing Period And Cropping Area In Liling City,Hunan Province Using Multi-temporal Remote Sensing Images

Rice is an important food product in the world.Acquiring rice area information accurately not only plays an important role in maintaining national food security,but also involves the formulation of government policies and the country's grain export volume.Remote sensing data has the advantages of high timeliness,wide monitoring range,and easy access.The method of using rice-specific phenological cycle for monitoring is the main method for rice remote sensing monitoring.Due to economic benefits,single-crop has increased in the proportion of total rice planting area.To ensure national food security,monitoring and analysis of single-crop planting area change is also particularly important.In this study,Liling City of Hunan Province was selected as the study area for single-crop area extraction.The characteristics of the single-season rice during the growth process were taken as the basis for extracting growth period and area information.The data sources for this article are the Landsat8-OLI data,MODIS 16-day synthetic vegetation index and MODIS 8-day composite surface reflectance data provided by the USGS and NASA website.Using the characteristics of high time resolution of MODIS data,the LSWI and NDVI time series curves of single-season rice were obtained from the surface reflectance data and vegetation index data,and the HANTS were used to smooth the outliers of the obtained time series to extract the growth cycle of single-season rice in Liling City,Hunan Province.Comparing the time series data of the single-crop extracted with the time data of the farming agriculture department,the time series characteristics of the LSWI and NDVI of the single-crop in each growth cycle of Liling City were obtained.However,due to the low spatial resolution of MODIS data,it is not conducive to use for further single-crop area extraction.The high-resolution Landsat8-OLI image can better reflect the surface features in the southern hilly region where the field is broken.It can effectively solve the mixed-pixel problem caused by the resolution,and has better accuracy.In this paper,high-resolution Landsat8-OLI data was used to obtain the characteristics of LSWI and NDVI in the key phenophase of single-crop,and a decision tree was created based on statistical data of various points to extract single-season rice planting areas.Comparing the extracted single-crop area information with the statistical yearbook data of Liling City,we can see that the accuracy of rice area information extracted by this method is 90%.Therefore,this method is used to extract rice area information in the southern hilly region where the field is broken is feasible.After the single-season rice area was extracted,the changes of the center of gravity of single-season rice planting and the change of single-crop rice planting area in Liling City were analyzed to discuss the possible reasons for farmers' choice of single-crop and double-crop and provide reference for the government to formulate policies to protect rice production.