Geocoding a Map

I have an image of a map and i store gps coordiantes on the map. I use the x and y coordinates and i store gps coordinates for those x and y coordinates. I cannot store gps coordinates for every x and y coordinate on my map. Cooridnates are only stored for certain areas of the map, but i want to be able to get the gps location or any area selected on the map.

Is there a way to calculate the gps coordinate for an area from another area on the map (lets say from the ar开发者_开发技巧ea that is already stored in the database). I want to be able to click anywhere on the map and get a gps coordinate for that area. Can someone please tell me how to achieve this.

If you want to be able to convert X,Y pixel coordinates to Latitude and Longitude coordinates, it's dependent on the map projection used by the map along with a few other variables. For starters I'd recommend this article: http://msdn.microsoft.com/en-us/library/bb259689.aspx Most online maps (Google, OpenStreet) use this approach. Hope that helps.