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.

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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.