施工测量中经常要遇到测定建筑物的坡面线和坡脚线（即建筑物坡面与地面的交线），它们通常是用逐次试放（先估计某一点是坡面上的一点，然后测量其距离和该处高程，再计算它是否恰好位于坡面上，如果不在坡面上，则应再次试放，这样逐次接近，最后定出坡脚点）的办法测定的。但是在山谷水库中。由于地势陡峭，量距困难，而且量距时的方向亦很难掌握使之和建筑物轴线垂直。因此，采用逐次试放法是十分繁杂的。笔者在梅山水库坝垛上游坡面的测放工作中曾试用“固定视准面法”测定坡脚点和坡面线，颇觉简便准确。这里将笔者在梅山水库实地施测的情况简单地介绍如下。 Construction surveys often involve measuring the slope line and slope line of a building (ie, the intersection of a building’s slope with the ground). They are usually used to test and release (first estimate that a point is a point on the slope, Then measure its distance and its elevation, and then calculate whether it is exactly on the slope surface. If it is not on the slope, it should be tested again and again, so that it is approached successively, and the method of determining the slope foot point is determined. But in the valley reservoir. Because of the steep terrain, it is difficult to measure, and the direction of the gauge is also difficult to grasp perpendicular to the axis of the building. Therefore, the use of successive trial and release methods is very complicated. The author tried the “fixed sight plane method” to measure the slope foot point and slope surface line in the surveying and releasing work on the upstream slope of the dam dam of Meishan Reservoir, and it was easy and accurate. Here, the author will simply introduce the situation in the Meishan Reservoir field test as follows.