flash map longitude and latitude to x,y

Question

Hi,

I am developing a map for my native itself. i mean i dnt need the whole world there but only my city. so i will enter the longitude and latitude of locations and the points should placed exactly on the location. i tried this methong and so many methonds.

            lat = (lat * -1) + 90;
            lon += 180;
            stationX = Math.round(lon * (mapwidth / 360));
            stationY = Math.round(lat * (mapheight / 180));

could any one please tell me how to make it.