Dear All:I'm correcting the coordinates of same airports of my scenery because, some maps has the DATUM: Porvisional 1956 and the SRTM data has WGS84, i read in my topographic mad that i have to add 12.4" Lat and 7.7" Long to my Prov1956 maps, this conversiton is for UTM Zone 18, for other zones and areas the conversion changes ? How many?I just have 3 maps with the old datum, but i have to correct the postion of a lot of buildings, macros, islands and son on.The good new are that my Phototerrain scenery match with the SRTM mesh terrain in valleys, mountains, shorelines....Thanks.Alfredo Mendiola Lima Peru

Hi Alfredo:ah, the wondrous (complicated) world of geographic projections...Sorry, I don't have a direct answer to your question but I suggest you try your luck with the freeware Geotrans software, which comes with about a billion different geoggraphic projections and allows for, you guessed it, translation between them. Hope this helps.http://164.214.2.59/GandG/geotrans/geotrans.htmlP.S. I never worked much with it myself so I can't tell you any particular tips; sorry.Cheers, Holger

Dear Holger:Thanks, for youl help, the program geotrans is what i wanted and needed, it will help me to convert my coordinates to the WGS84 datum for a specific area, because the convertion units changes from Lat and Lon zones.Alfredo Mendiola LoyolaLima Peru