基于时序归一化植被指数的冬小麦收获指数空间信息提取

为获取农作物收获指数（HI）空间分布信息，该研究充分利用遥感技术，以冬小麦为例，利用时序归一化植被指数NDVI构成的作物生长过程曲线提取MODIS NDVI阶段性累积特征参数，并用生殖生长关键阶段和营养生长关键阶段对应的NDVI累积参数比值HINDVI_SUM构建了用于反演冬小麦收获指数的参数，并建立了参数HINDVI_SUM与冬小麦实测收获指数的定量关系，利用上述定量关系实现作物收获指数空间信息的提取。经过对反演冬小麦收获指数的精度验证，结果表明，利用构建参数HINDVI_SUM在区域范围内反演冬小麦收获指数取得了较好的效果。其中，冬小麦收获指数预测的平均相对误差为2.40%，均方根误差（RMSE）为0.02，证明了该研究利用时序NDVI构建参数HINDVI_SUM反演区域冬小麦收获指数空间信息的方法准确性和可行性。

Retrieving the spatial-explicit harvest index for winter wheat from NDVI time series data

Crop harvest index (HI) is critical to crop yield estimation and prediction. In this paper, a novel technique to extract spatial-explicit HI information for winter wheat from remotely sensed data was developed. Based on the understanding of the intrinsic features of HI and crop phenology expressed by NDVI time series data, a derivative index HINDVI-SUM for the inversion of HI from remotely sensed data was devised. HINDVI-SUM was defined as the ratio between accumulated 10-day NDVI for reproductive and vegetative stages of winter wheat. Then the relationship between HINDVI-SUM and the in-situ HI of winter wheat was tested in the study area in North China Plain. Finally, the established relationship to retrieve the spatial-explicit crop harvest index information from remote sensing data was applied in the study area. After validation, the accuracy of the retrieved HI of winter wheat was satisfactory. The mean relative error of the retrieved crop HI was only 2.40% and RMSE was only 0.02. It was shown that the method developed to construct HINDVI-SUM and extract the harvest index for winter wheat from MODIS NDVI time-series data was feasible and reliable.