当我們要估計一片森林共有多少材积(即森林中木材的总体积)时,就要求出这片森林的平均树高,如果一棵棵地去量,然后求出平均数,这实际上是不可能的,而且也没有必要。往往总是选择几块样地,求出样地上的平均树高,以它来代替全体的平均树高。但由于样地上树木的数目还是非常之多,如果逐一測量,仍須很大的人力和物力,日本有一个森林工作者他想出了一套簡易的方法,这种方法就是現在我們准备介紹的! 如果我們选定了一块样地,它的总面积是D,树木的总数是N。我們用h_i表示第i棵树的树高,那末我 When we want to estimate how many volumes of forest a forest has (ie, the total volume of wood in the forest), the average tree height of this forest is required. If we measure the number of trees and then calculate the average number, this is actually not. It is possible and unnecessary. Often choose a few plots, find the average tree height in the plot, and replace it with the average height of the entire tree. However, because the number of trees in plots is still very large, if one by one is measured, there is still a lot of manpower and material resources. In Japan, there is a forest worker who came up with a simple method. This method is now we are ready to introduce If we choose a plot, its total area is D, and the total number of trees is N. We use h_i to denote the height of the i-th tree. Then I