Can anyone give me the specific method of calculation without using a map (or a website that does it) where an absolute compass direction (from A to B) is calculated from the 2 latitude and longitude coordinates of A and B?

kevinatilusa

I believe this method will work. Assume that A is to the west of B (if this is not the case, you can always just swap which is A and which is B, then move 180 degrees opposite on the compass). Let x be the difference in latitude between B and A (take the Latitude of B, subtract the Latitude of A, treating southern hemisphere latitutes as negative), and let y be the difference in longitude (longitude of B-longitude of A, this should be less than 180 degrees since we assumed B is east of A). Divide x by y to get a third number z. Now take the inverse tangent (a trigonometric function) of z. That is the number of degrees counterclockwise from due east that B is from A (which may be negative if B is south of A). Basically what this is doing is imagining the two points to be on a Mercator projection map (latitude lines all straight left-right, longitude ones all straight up-down) and going from there. This should be okay since the Mercator projection preserves angles (but not areas). Jul 31 03, 7:42 PM