一种基于TVDI模型的煤田温度异常区面积提取方法研究

选用Landsat 8 资料构建了地表温度（Ts）与归一化植被指数（NDVI）的Ts-NDVI特征空间，计算了温度植被干旱指数（TVDI）。利用MODIS温度产品数据和实地野外采样数据进行精度验证确定煤田火区TVDI阈值。通过对遥感影像的地表热异常信息进行定性与定量分析继而对煤田温度异常区边界信息进行挖掘。结果表明：（1）利用野外实测土壤相对含水量进行验证，反演值与实测值的相关系数R²=0.66，表明干旱指数的反演精度较高，相关性较好。（2）TVDI模型对温度呈现出较高的敏感性，二维散点图集中在1∶1 线上，对NDVI的敏感性较低，有利于识别温度异常区。（3）利用MVC最大合成法，建立TVDI-MVC作为精度验证数据，火区面积为5.03 km²，其中TVDI-SC提取火区精度最大为98.50%，TVDI-SW2提取火区精度最小为88.98%。可见煤田温度异常区范围较广，潜在的灾情恶化较严重。

A coalfield fire area extraction based on TVDI method

It is universally acknowledged that coalfield fire has direct impacts on the efficient utilization of coal resources and economic development,so does the coalfield of east Junggar Basin in Xinjiang Uyghur Autonomous region. In this paper,Land surface temperature(Ts)and normalized difference vegetation index(NDVI) were obtained from Landsat-8 satellite data,and were used to create the feature space of Ts-NDVI,then a dryness index-Temperature Vegetation Dryness Index(TVDI)was calculated through the dry and wet line equation. The accuracy was verified and the reference upper boundary was determined by adopting MODIS LST product data. Through quantitative analysis of the information on surface heat anomalies using remotely sensed data,the dynamic variation rules and tendencies of sub coal fires were summarized. Because TVDI is much more sensitive to Ts than NDVI,extracting the coalfield fire boundary with TVDI method in the coalfield with fewer vegetation coverage is better. The results show as follows:(1)the correlation coefficient of the inversion value verified by using field measured soil moisture and measured value is R²=0.66,this demonstrates that the accuracy of TVDI is acceptable;( 2)TVDI presents a high sensitivity to temperature,while a lower sensitivity to NDVI,thus can be used to identify the fire area of high temperature;(3)the biggest area extracted by TVDI-MW method is 5.54 km², and the longest boundary is up to the 93.7 km extracted by TVDI-SW2. TVDI method performs well in extracting the information in uncomplicated underlying surface,however,the coal dust could be deposited at the land surface and the root of vegetation around the mining area,which may result in a higher value of Ts and also disturb the accuracy of Ts. Therefore,there is a wide range of high-temperature coal fire area,and the potential deterioration may be more serious.