How to calculate area which was compose with mulit- Coordinates ?

Question

Hi, dear coders ,

as topic, the Coordinates value (Latitude and Longitude) is known , these Coordinates will compose as polygonal area , my question is how to calculate the area of the polygonal that is base the geography ?

thanks for your help .

Answer 1

If I understand your question correctly - triangulation should help you. Basically you break the polygonal to triangles in such a way that they don't overlap and sum their areas.

Answer 2

First you would need to know whether the curvature of the surface would be significant. If it is a relatively small then you can get a good approximation by projecting the coordinates onto a plane.

1. Determine units of measure per degree of latitude (eg. meters per degree)
2. Determine units of meature per degree of longitude at a given latitude (the conversion factor varies as you go North or South)
3. Convert latitude and longitude pairs to (x,y) pairs in the plane
4. Use an algorithm to compute area of a polygon. See StackOverflow 451425 or Paul Bourke

If you are calculating a large area then spherical techniques must be used.