照相法在植被覆盖度测量中的误差分析

Error analysis of plant coverage measurement by overhead photograph

植被覆盖度是遥感中的一个重要参数,其测量准确性对于地表水文过程和地面生物过程有着重要作用.小尺度植被盖度测量方法主要为简单目测法、仪器测量法和遥感解译法,其中照相法由于仪器获取方便、操作简易,是研究中常用的测算方法.然而由于中心投影造成的相片变形,降低了图片的利用率,同时导致覆盖度测量结果存在误差.利用计算机模拟地物,研究照相法的误差,并结合实际植被覆盖度测量过程和植被属性建立几何模型,提高照片的使用效率,同时分析照相法观测的植被盖度的误差大小,并给出误差纠正函数以及实际中运用该函数提高精度的步骤.

Vegetation coverage is an important index in remote sensing research. It serves many other fields as an essential parameter, such as hydrology, ecology and agriculture. Overhead photograph is the main measurement of the vegetation coverage because of its easy-operation. The error of the camera imaging, caused by central projection, is one of the main factors contributing to the result＇s accuracy. Based on the computer simulation of constructing 3D models, this paper puts forward a correction equation with geometry theory in order to reduce the influence of central projection. This correction is deduced from practical vegetation coverage researches and related to certain plants＇ property, which is of practicability.