surface

This figure provides a simple cross-sectional illustration of the kind of issues that arise. We wish to determine the distance separating points A and B. If A and B are not too far apart (e.g. less than 10 km) we could use a high precision laser rangefinder to establish the slope distance between A and B, assuming there is no atmospheric distortion. In practice, there will be some distortion and the laser wave path will need to be adjusted in order to provide an estimated slope path distance. This, in turn, will require further adjustment if it is to be referenced […]