Survey Method of Vegetation Cover in Urban Areas by Use of Aerial Photographs

航拍照片（比例为1:10 000- 1:25 000）定期在市区拍摄。这些照片可用于测量地球上各种特征的空间分布。利用以上航拍照片，对城市地区的真实植被面积进行了估算。下面介绍两种方法。两种方法都是基于对试验区超过网格（50m*50m）植被面积的立体观测。一种是常用的点抽样方法。另一种是直接用眼睛在网格区域内估计植被面积的方法。这两种方法对城市植被面积估算都有一定的参考价值。对于大比例尺照片的观测者来说，点采样法是一种省时、简便的方法。第二种方法对1:25 000比例尺的照片有利，因为误差小，观察障碍小。

Aerial Photographs (1 : 10,000-1 : 25,000 in scale) are regularly taken in urban area. These photographs can be used for surveys of spatial distributions of various features on the earth. By use of the above aerial photographs, estimations of real vegetation areas in urban areas are tested. Two methods described below are examined. The both methods are based on stereometric observation of vegetation areas covering over grid areas (50m*50m) in test regions.The one is the point sampling method usually used. The other is a method of direct estimation of vegetation areas with the eyes in the grid areas. The both methods are useful for the vegetation area estimation in urban area. The point sampling method is a timesaving and easy task to an observer for large scale photographs. The second method is advantageous for the photographs of scale 1 : 25,000 because of small errors and little obstacles for observation.