Question

This question have been asked many times but i want the answer which i can use in a php application.

The closest answer i found was this

int x =  (int) ((MAP_WIDTH/360.0) * (180 + lon));
int y =  (int) ((MAP_HEIGHT/180.0) * (90 - lat));

I don’t need to show the map or something. I just need to calculate it.

What should be the MAP_WIDTH and MAP_HEIGTH if i use the above formula ?

Answer 1

There is no such thing as x and y coordinates for the earth. At most, you could compute x, y and z. Note that Euclidean distance then would travel through the earth surface.

It should also be pretty obvious that any x-y based system will produce completely inaccurate results close to the poles and close to the date line…

Keep the data as it is – in latitude, longitude (and height, if available) – and instead of computing Euclidean distance, use the great circle distance. Unless you have detailed information about the actual shape of the earth, the common great circle approximation with a sphere is the best you can do. And actually quite easy to use.

http://en.wikipedia.org/wiki/Great-circle_distance