基于近地高光谱与TM遥感影像的冬小麦冠层含水量反演

为探讨利用近地高光谱和TM遥感影像数据评估作物冠层水分状况的可行性,以北京顺义通州为研究区域,以冬小麦为研究对象,首先基于Landsat TM5的光谱响应函数,利用地面实测的冬小麦全生育期冠层高光谱窄波段反射率数据来模拟TM5卫星宽波段反射率,然后利用模拟的TM5数据的NIR波段(第4波段)和2个SWIR波段(第5和7波段)反射率分别构建水分指数(WI)和归一化差异水分指数(NDWI),并利用地面实测数据建立冠层叶片含水量(LWC)和等效水厚度(EWT)的遥感估算模型,最后选取最优的水分估算模型,利用TM5卫星遥感影像数据对研究区域小麦冠层水分含量进行反演与应用。结果表明,利用TM5数据中SWIR第5波段比第7波段构建的水分指数更有优势;WI对估算LWC的效果较好,而NDWI在EWT估算方面效果较好,应用TM5宽波段模拟数据模型验证的冬小麦冠层含水量的r2和RMSE分别为0.57和0.51、3.89%和0.024。同时从TM遥感影像的反演结果来看,开花期的冬小麦冠层水分高于拔节期。

Inferred Water Content of Winter Wheat Based on Ground Hyperspectral and Remote Sensing Data of TM5

The objective of the study is to explore the feasibility of crop water status with hyper spectral and TM sensing data.Taking Shunyi and Tongzhou in Beijing as the study area in this paper. In order to monitor canopy water content of winter wheat, canopy spectrum of winter wheat with narrow band were resampled to broad band according to relative spectral response function of TM5 based on the measured ground spectral data during the whole stage of winter wheat. And then, typical water index WI (Water Index) and NDWI (Normalized Different Water Index) were estimated by NIR band and two SWIR bands (1 550~1 750 nm, 2 080~2 350 nm). The models of estimating LWC and EWT were established using the measured ground data. Finally, the optimal estimation model was chosen and combined with TM5 satellite remote sensing image data, the wheat canopy water content was estimated and applied in the study area. The results showed that the fifth band of TM5 was better than the seventh band in estimating canopy water content of winter wheat. Meanwhile, the relationship between LWC and WI was better, and the relationship between EWT and NDWI was better. And then LWC and EWT were estimated by using simulated data of TM5 at the whole stage with the r and RMSE being 0.57 and 0.51, 3.89% and 0.024, respectively. Meanwhile, the canopy water content of winter wheat was higher at anthesis stage than at jointing stage from the inferred results of TM5 remote sensing data.