Then based on the method of dimidiate pixel model , the current model is improved , and the model of deriving vegetation fraction from normalized difference vegetation index ( ndvi ) 然后在像元二分模型的基础上对已有模型进行改进，建立用ndvi归一化植被指数估算植被覆盖度的模型。
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3 . characteristic points are established through projecting images of regular points to measured surface . space dimidiate coding method which is called rough match and correlation technology , centroid technology , corner detect technology which are called precise match are used to acquire characteristic points accurately 将空间规则点图案投射到被测物体表面形成特征点，然后利用空间二分编码粗略获得空间特征点（称为粗匹配） ，再利用自相关技术、质心技术和角点技术精确获得空间特征点的图像坐标（称谓细匹配） 。
