林业工作者通常认为,用网点板在地图或航空象片上作抽样估测面积是方便的。但精度究竟如何?应该研究。我们知道,评定精度的标准差是用统计方法估算的。在这里,假定每一个网点是一个简单随机观测值。这是无效假说,因格网都是系统布点。然而这种方法已被 Forestry workers often find it convenient to sample areas on maps or aerial photographs using halftone plates. But exactly how accurate? Should be studied. We know that the standard deviation of the assessment accuracy is statistically estimated. Here, assume that each dot is a simple random observation. This is an invalid hypothesis, because the grid is the system distribution. However, this method has been