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航空象片50年代就开始应用于森林资源调查,但多数是独立的调查,即是说同一地区利用象片调查,尽管前后期象片拍摄时间不同,而调查资料没有有机联系。近年来有的学者利用成数抽样方法,在试验总体中按预先计算的样本单元数,布设成千上万个样点,在两期象片上的同一点上进行土地资源判读,然后统计各类土地的点数,按照一定的公式计算出各类土地成数的估计值及误差,并换算成面积,比较两期各类土地面积,可以得出各类土地面积
Aerial photos began to be applied to forest resources surveys in the 1950s, but most of them were independent surveys. That is to say, image surveys were conducted in the same area. There was no organic link between the survey materials despite the different filming dates of the previous period and the later period. In recent years, some scholars make use of the sampling method of the number, in the total test in accordance with the pre-calculated number of sample units, the layout of thousands of sample points in the two images on the same point on the interpretation of land resources, and then statistics of various types Land points, according to a certain formula to calculate the estimated value of various types of land into the value and error, and converted into area, comparing two types of land area, you can come to all types of land area