RECOVER MAP 3.1.3.1 Water Conservation Area 2 & 3 Elevations

The U. S. Geological Survey (USGS) Airborne Height Finder (AHF) system was used to perform topographic surveys in Water Conservation Areas 2 and 3A. The AHF is a helicopter-based instrument that uses a GPS receiver, a computer, and a mechanized plumb bob to make measurements.美国地质调查局（U. S. Geological Survey, USGS）机载测高系统（Airborne Height Finder, AHF）被应用于水资源保护区2号与3A区的地形测绘工作。该系统为搭载于直升机平台的测绘仪器，通过集成GPS接收机、计算机与机械化铅锤完成测量作业。