| Qujing is the largest production base of high quality flue-cured tobacco in Asia.Flue cured tobacco is one of the most important economic crops for farmers in Qujing City.The extraction and change monitoring of flue-cured tobacco planting area is of great significance to grasp the agricultural income of farmers and maintain the development of regional tobacco industry.Remote sensing image processing is the main means to quickly obtain and monitor crop planting information.At present,the extraction and monitoring of crop planting information mainly adopts a single computer processing method.However,this method is limited by the processing speed and is not suitable for the extraction of crop remote sensing information in long time sequence and large area.Qujing City is located in Yunnan Guizhou Plateau.It is difficult to extract flue-cured tobacco by remote sensing because of cloudy and rainy weather,broken farmland and complex crop types.Google Earth engine cloud platform can quickly acquire and process a large number of remote sensing data,which provides platform support for long-time series and large-scale flue-cured tobacco extraction.Arc GIS is a comprehensive and scalable GIS data processing and analysis platform,which provides a powerful remote sensing image change monitoring tool and an important technical means for crop change monitoring.Therefore,based on Google Earth engine cloud platform and Arc GIS software platform,using Landsat 8 and sentinel-2 satellite images,Remote Sensing Extraction and monitoring of flue-cured tobacco planting area in Qujing City from 2015 to 2020 were carried out.The main research contents and conclusions are as follows:(1)Extraction of flue-cured tobacco remote sensing information based on multi feature and multi classification method optimization.Firstly,the key phenological period of flue-cured tobacco classification was analyzed to obtain the best time phase data of flue-cured tobacco classification;secondly,the texture,spectrum,terrain and tassel features were extracted,and the J-M distance formula was used to calculate the sample separation degree to obtain the optimal feature of classification;Then,support vector machine,classification and regression tree,random forest classifier and feature combination experiments were carried out,and the random forest classifier was selected to extract the flue-cured tobacco planting areas in 2015 and 2020,and the accuracy of the results was evaluated;finally,the spatial distribution characteristics of flue-cured tobacco planting areas in 2015-2020 were analyzed.The results showed that the best time of flue-cured tobacco classification was from late April to late May.The feature optimization method based on J-M distance improves the separability of samples.The method of random forest classifier combined with multi feature combination has high accuracy.In 2015 and 2020,the average producer precision of products in the two periods of flue-cured tobacco planting area is 87%,the average user precision is 89%,the average overall precision is 92%,and the average kappa coefficient is 0.89.In 2015 and 2020,the area of flue-cured tobacco in Qujing was367800 hectares and 222700 hectares respectively.The flue-cured tobacco in Qujing was mainly distributed in Luliang County in the southwest,Zhanyi District in the middle and Xuanwei City in the northeast.(2)Study on monitoring changes of flue-cured tobacco planting area based on spatial analysis.Firstly,the two images were superimposed by the post classification comparison method to get the information map of flue-cured tobacco change from 2015 to 2020;Secondly,the area change of flue-cured tobacco was analyzed in time and space by using the method of partition statistics;secondly,the land use transfer matrix of flue-cured tobacco was calculated to analyze the type and direction of tobacco change;finally,the dynamic degree of tobacco area change was calculated to get the change rate of tobacco area.The results showed that the total area of flue-cured tobacco in Qujing City and all districts and counties showed a decreasing trend from 2015 to2020.The area of flue-cured tobacco in Xuanwei City decreased by 23100 ha at most,while that in Malong County decreased by 7300 ha at least.The annual decreasing rate of Flue-cured Tobacco Area in Fuyuan County was the fastest(-11.8%),and that in Malong county was the slowest(-4.9%).(3)Based on qualitative and quantitative analysis,the driving factors of tobacco planting area change were analyzed.Firstly,the main factors influencing the change of flue-cured tobacco in the study area were economic development,annual average precipitation,production cost per mu of flue-cured tobacco and purchase price of Fluecured Tobacco by combining qualitative method with principal component analysis.Finally,the driving factors influencing the change of flue-cured tobacco were analyzed.The results showed that the main driving forces affecting the change of flue-cured tobacco in Qujing City were economic development,annual average precipitation,production cost per mu and purchase price of flue-cured tobacco. |
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