On 2001-10-24 14:30, David Simmons wrote:
On 2001-10-24 14:09, Ben Benoy wrote:
However, long distance surveying also has to take into account atmospheric refraction, etc
Actually, you can survey long distances without worrying about atmospheric refraction. The method is called "triangulation" which is not the same thing as the means of determining distances to astronomical objects.
What is done for long distance surveying is to lay out a proposed line that is to be surveyed. Then the line is broken into short segments so that refraction and, yes, the curvature of the earth can be ignored. Each short segment is one leg of a triangle that closes back to its individual starting point. This allows each individual survey line segment to be closed back on itself so the errors do not accumulate. Futhermore, the surveyor knows at all times what the error of closure is and if it is greater than the survey specification allows, the segment can be resurveyed to get back within specs.
There are interesting tricks to all trades.