Dear All:Could you tell me how to convert bitmaps coordinates to LAt LON coordinates to show in a edit box the LAT LON of my custom map like Ground2K where the user must set the NW corner and SE corner?I'm using C++ and Java.Thanks.Alfredo Mendiola LoyolaLima Peru

Hi Alfredo:I'm not sure I understand completely what you'd like to achieve. Basically, to "georeference" a bitmap you need to know at least two control locations with known ground coordinates, and they should be as far apart as possible.If you have those, say P1 and P2 (in decimal degrees), then you can calculate the width and height (in decimal degrees) of each bitmap pixel:picel width = (longitudeP2 - longitudeP1) / (bitmap-columnP2 - bitmap-columnP1)pixel height = (latitudeP2 - latitudeP1) / (bitmap-rowP2 - bitmap-rowP1)With that information you can then figure out the lat/long of the image corners.Is that what you were looking for?Cheers, Holger

Dear Holger:Yes but i want to show the map coordinates under the mouse pointer in two edit boxes one to show the Latitud and other to show the Longitud.Like Ground 2K, did you use that program.Thanks.Alfredo Mendiola LoyolaLima Peru

Dear Holguer:I know that work with 3 points is better than work with 2 points, what is the formula with 3 points to georeference a Bitmap?Thanks.Alfredo MEndiola LoyolaLima Peru