利用未纠正航片确定汇水面积的方法

为了在小桥涵勘测中更好地利用未经纠正的航片量测汇水面积，必须提高量测的精度。本文分析了航片上的倾斜误差和投影差，并推导出在倾斜航片上量测汇水面积时倾斜误差和投影差的改正系数，给出了改正方法。实践证明，其量测精度不低于１／７０，这对精度要求不高的农林资源调查，具有普遍的实用价值。

METHOD OF DECIDING AREA OF CONVERGING WATER BY NOT RECTIFIECL AERIAL PHOTOGRAPH

The surveying precision must be improved in order to decide area converging water by not recited aerial photograph in the course of surveying small bridges and culverts. This paper not only correct coefficient correction of error of tilt and relief displacement but also offers method to define area of converging water by use of tilt-photograph on the basis of analysis of influence caused by error of tilt and relief displacement.It is proved by practice that the surveying precision of this method is not less than 1/70 and the method has also practical value in invenstigation of forest-agriculture resoures.