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利用MODIS植被指数时间序列这一特性,以北京市通州及周边为实验区,冬小麦种植面积为研究对象,提出了农作物种植面积指数模型(Pan-CPI模型)的概念,并构造了冬小麦特征物候期植被指数与种植面积的定量函数关系,通过样区TM影像求解关键参数,对研究区冬小麦种植面积测量方法进行了试验研究。研究结果表明:(1)Pan-CPI模型能够很好地反映特定目标农作物种植面积状况,为基于植被指数时间序列影像识别农作物种植面积提供了新方法;(2)精度分析结果表明:Pan-CPI模型具有很高的稳定性,且不受样本变化的影响,只要达到满足模型计算的样本量(如:5%),多次测量结果间具有很好的一致性。选取MODIS6×6像元大小的窗口时,TM样本的复相关系数(R2)稳定在0.85左右,与TM结果比较,窗口相对精度稳定在95%左右,区域精度稳定在92%以上,经调整的区域精度高达96%以上;(3)对于种植结构复杂、目标作物种植破碎的地区,Pan-CPI模型可以充分利用MODIS植被指数时间序列的优势,有效改善TM单时相和多时相提取信息因时相缺失无法表征作物变化的不足。
Using the MODIS vegetation index time series feature, the winter wheat acreage was taken as the experimental area in Tongzhou and surrounding areas of Beijing. The concept of crop-acreage index model (Pan-CPI model) was put forward and the characteristics of winter wheat According to the quantitative function of vegetation index and plantation area, the key parameters were solved by the TM images of the plots. The method of measuring the winter wheat acreage in the study area was studied. The results show that: (1) The Pan-CPI model can reflect the planting area of a specific target crop well and provide a new method for identifying crop planting area based on time-series images of vegetation index; (2) The results of precision analysis show that Pan- The model has high stability and is not affected by sample changes. As long as the sample size (for example, 5%) that meets the model calculation is satisfied, there is a good consistency between multiple measurement results. When the MODIS6 × 6 pixel size window is selected, the complex correlation coefficient (R2) of TM samples is stable at about 0.85. Compared with the TM results, the relative accuracy of the window is stable at about 95% and the region accuracy is stable at 92% (3) The Pan-CPI model can make full use of the advantages of the MODIS vegetation index time series in the areas with complex planting structure and the target crop planting and fragmentation, and effectively improve the information extraction time of single and multiple phases of TM due to Phase loss can not characterize the deficiencies of crop changes.