On Mon, Feb 21, 2011 at 7:01 PM, Frank Warmerdam <warmer...@pobox.com> wrote: > On 11-02-21 12:43 PM, Jorge Martin wrote: >> >> Hello, >> >> >> I have a big doubt about transforming one point from UTM to >> Lat/long. >> I have to make the resampling of a Lat/long image. The target image is UTM >> with >> 2.5 resolution. To create the target image I use GDAL, so I have to set >> the UTM >> zone, so I set this zone to the zone corresponding to the top left corner >> of >> the source image (Lat/long). >> >> When I am reading the all the points of the target (UTM) image and >> finding the corresponding lat/long coordinates into the source image. I >> have to >> transform these points from UTM to Lat/Long. I case the source image >> covers >> more than one UTM zone, the transformation between this two coordinate >> system >> is not the right.Because the Lat/long of the initial image may corresponds >> to >> a UTM zone different than the one I have fixed for the grid. >> >> Is there any way to make this transformation taking into account this >> problem? > > Jorge, > > I'm not positive I follow your problem, but in the situation of resampling > an image into a UTM projection when the image overlaps two zones you can > just pick one with the greatest overlap and use that. > > There is nothing that says you can't reproject to a given utm zone even > outside it's zone bounds. But keep in mind that the further you get > from the central meridian of a zone, the greater the distortion and error > in how the equations are evaluated. So you don't want to be using a > UTM zone several zones away from the image. > > As a rule of thumb, I'd suggest using the center of the image to decide > on a utm zone. > > Best regards, > -- > ---------------------------------------+-------------------------------------- > I set the clouds in motion - turn up | Frank Warmerdam, > warmer...@pobox.com > light and sound - activate the windows | http://pobox.com/~warmerdam > and watch the world go round - Rush | Geospatial Programmer for Rent > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev >
Hi Jorge, As Frank said, I'd use the center of the image to decide UTM zone. I have experience with images covering Spain area (UTM zone 28 for Canary Island, and 29-31 for Spain). I've obtained positive results using zone 30 for all Spain except Canary Island. Best regards, -- Jorge Arévalo Internet & Mobilty Division, DEIMOS jorge.arev...@deimos-space.com http://es.linkedin.com/in/jorgearevalo80 http://mobility.grupodeimos.com/ http://gis4free.wordpress.com http://geohash.org/ezjqgrgzz0g _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
