我们第二三角队在平原地区的宜陈段及湘阳区选点,主要是靠瞭望杆来解决通视问题和确定标高。由于高杆承受风力以致本身摆动,且为高空作业,环视图的绘制,就是一个难于解决的问题。经过半年多来的摸索,初步找到两个方法,虽然在环视图的质量上,仍不能达到如在地面上绘的那样精确,但已基本上解决了这个问题。兹分绍如下: Our Second Triangle Teams selected sites in Yichang Section and Xiang Yang District in the plains to mainly rely on sighting poles to solve the problem of viewing and determine elevations. As the high pole to withstand the wind itself caused by swinging, and for high altitude operation, drawing the ring view is a difficult problem to solve. After more than six months of exploration, two methods were initially found. Although the quality of the ring can not be as accurate as that painted on the ground, this problem has been basically solved. We hereby introduce the following: