MODIS数据的水浇地提取

Extracting irrigated land based on MODIS data

水浇地是土地覆盖分类系统中的一个重要类型,依据水分亏缺指数(WDI)与土壤水分的相关性,计算了监测时间内WDI的变化情况,用降雨资料去除了由于降雨引起的WDI的变化,进而提取了研究区的水浇地分布。结果表明:(1)提取出的水浇地在数量上与统计资料相比,除山西省偏差相对较大外,其余各省偏差均小于7%,提取出的结果与统计资料具有可比性。(2)提取出的水浇地在空间上多成片出现在河流、湖泊、水库附近、灌区和绿洲上,与已知的水浇地集中区一致。(3)利用TM影像对提取结果进行了初步判断,其中山西省的正确率较低,只有64%,其余各省正确率均在70%以上,新疆的正确率最高为92%。

Irrigated land is one of the most important parts in land cover classification system, but until now it has seldom been reported about extracting it from remote sensing data and monitoring its dynamic change. The existing researches are focused on the land use-cover change （LUCC） and the irrigated area mapping, so the study on extracting irrigated land is much more important. On the basis of close relationship between water deficit index （WDI） and soil water content, this paper firstly combines two neighbor NDVI and the surface-air temperature （Ts-Ta） and conforms one Vegetation Index Temperature （VIT）. It makes the timely incomparable WDI comparable and then computes the change of WDI during the monitored period. Secondly it infers the change of soil water. Thirdly it removes the rainfall＇s influence under some assumption and extracts the irrigated land of the survey area. Results show that comparing with census data all the deviation is below 7% in the survey area except Shanxi province, which means that the extracted results are comparable with census data. Extracted irrigated land mainly distributes around rivers, lakes, and reservoirs or on the irrigated regions and oasises. The results are consistent with the centralized region which has abundant irrigated land known before. The results are checked elementarily using TM images. All the precisions ate above 70% except in Shanxi province. The precision in Xinjiang municipality is the highest.