b. Inverse Computation
An inverse computation is used to determine the distance and direction between two coordinate pairs. The computations involved are basically the same as those for determining a line's new length and direction from its adjusted lats and deps.
For the traverse shown in Figure F-7, how would we determine the length and direction of the line from point T to point R?
Length and Direction Between Nonadjacent Points
Knowing the coordinates of the two points, we can determine the latitude and departure of the line from the coordinate differences, Figure F-8.
Note that the differences are the To point values minus the From point values.
|-90° ≤ ß ≤ 90°|
The mathematic signs on the coordinate differences determine the direction quadrant, Figure F-9.
Converting ß to a Direction
If X and Y coordinates are used, remember that Y corresponds to N and X corresponds to E.