单词trig point
un.: 三角测量基点网络: 澳天露三角系列；澳天露蓝三角；三角点
（地图制作和使用者设的）三角点:
a position on a high place used as a reference point , especially by people who make and use maps. It is usually marked on the ground by a short stone pillar .
三角测量基点