Le mercredi 09 décembre 2015 20:55:53, Djordje Spasic a écrit : > Thank you for the reply Even. > > Based on your equation one can identify the UTM zone. Which in this case > for Barcelona is: 31. > > How can I identify the EPSG projection based on UTM zone 31?Is it possible > to identify it with some formula too?
Add 32600 to the UTM zone for the northern hemisphere, or 32700 for the southern hemisphere. > > Kind regards, > Djordje Spasic > > > From: Even Rouault <[email protected]> > To: [email protected]; Djordje Spasic <[email protected]> > Sent: Wednesday, December 9, 2015 7:43 PM > Subject: Re: [gdal-dev] how to pick the correct projection > > Le mercredi 09 décembre 2015 19:23:16, Djordje Spasic a écrit : > > Hi, > > > > I am downloading an open source .asc elevation files from > > opentopography.org. I attached one of them in this email. Once > > downloaded .asc elevation file need to be projected from WGS84 datum > > (EPSG 4326) to Universal Transverse Mercator. Here is an example of how > > this looks like in python GDAL for Barcelona Spain downloaded elevation > > model: gdalwarp -s_srs EPSG:4326 -t_srs EPSG:32631 -r cubic > > BarcelonaWGS84.asc > > projectedToUTM.tif So in this case the EPSG:32631 has been used as a > > projection (it hasn't been picked by me), it was googled. > > > > But how do I know which projection to pick, depending on the location for > > which the elevation data is downloaded? I googled a bit, and there are > > few articles online, which suggest picking the right EPSG projection > > based on UTM zone to which the downloaded elevation model belong > > to:https://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate > > _ system#/media/File:Utm-zones.jpg > > > > But I am not sure I understand how to choose the EPSG projection based on > > UTM zone. > > > > How can this be done? > > Formula given in > http://stackoverflow.com/questions/9186496/determining-utm-zone-to-convert- > from-longitude-latitude > > long2UTM <- function(long) { > (floor((long + 180)/6) %% 60) + 1 > } > > Take the longitude of the central point of the source raster as input > > Just thinking it could be interesting to have gdalwarp accept -t_srs > AUTO:42001 to do that automatically: > http://cite.opengeospatial.org/OGCTestData/wms/1.1.1/spec/wms1.1.1.html#au > to_projections.42001 > > > Thank you for the reply. > > > > Kind regards, > > Djordje Spasic -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
