利用十万分之一或五万分之一的地形图来求小桥涵汇水面积,确可节省大量实测的人力。过去,关于这方面的介绍不多,希望已采用的地区,将新的经验或心得写给本刊,特别是所测的线路,如何正确地反映在地形图上;以及在大比例尺的地形图中,所求得的汇水面积,如何能达到必要的精确度。 The use of one hundred thousandth or one ten thousandth of a topographic map to seek a small bridge culvert catchment area, can indeed save a lot of measured human. In the past, there was not much introduction in this area. We hope that the adopted areas will write new experiences or experiences to our magazine, especially how the measured routes are correctly reflected in the topographic maps. And in the case of large-scale topographic maps In the area of ​​the catchment, how can we achieve the necessary accuracy?