Fast forward to the 1950s, and surveyors got a bit of help from photogrammetry, detailed photos taken from the air that they could use to measure heights and distances.

时间很快来到20世纪50年代，测量员们从摄影测量学中得到了一些帮助，他们可以用从空中拍摄的高清照片来测量高度和距离。