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在以前介绍的遥感判读与地面样地相结合的两相抽样中 ,地类合并后的样地平均蓄积是根据合并前各地类的样地平均蓄积按各地类的实测样地数加权计算的。这种算法会引起三个问题 :一是合并后地类的总蓄积不等于原地类的蓄积之和 ,即不满足加法公式 ;二是如果最后要将总体合并成一个地类 ,则不论遥感样地数量有多大 ,正判率有多高 ,总体的蓄积始终不会变化 ,因为总体平均蓄积就等于总体所有地面样地的算术平均 ,与遥感样地无关 ;三是不方便多重合并。笔者认为 ,地类合并后的平均蓄积根据合并前各地类的平均蓄积按各地类修正后的面积成数加权计算会比较合理 ,因为这样会避免上述问题。
In the two-phase sampling combining remote sensing interpretation and ground sample introduction, the average accumulation of sample plots after land consolidation is weighted according to the average sample plots of all regions before consolidation, weighted by the number of sample plots of each type. This algorithm will cause three problems: First, the total area of the combined terrain does not equal the sum of the accumulation of the terrestrial category, that does not satisfy the addition formula; the second is if the final merged into a land class, regardless of remote sensing The number of plots is large, the rate of positive judgment is high, and the overall accumulation will not change. The overall average accumulation is equal to the arithmetic average of all the plots on the whole and has nothing to do with remote sensing plots. Third, it is not convenient for multiple consolidation. In the author’s opinion, the average accumulation after the merging of land categories will be more reasonable based on the weighted average of the area stocks after the merger based on the average accumulations of all the regions before the merger, as this will avoid the above problems.