On Jan 15, 2010, at 8:29 PM, Frank Warmerdam wrote: > Eli Adam wrote: >> Hi all, I'm having some trouble using gdalwarp to mosaic ArcInfo Binary Grid >> files to vrt. >> Here is what I want to do and works in .tif. I mosaic the three grids be... >> to test2.tif: gdalwarp -t_srs "EPSG:2913" -s_srs "EPSG:2994" -srcnodata "0 0 >> 0" -dstnodata "0 0 0" -of GTIFF be44123g8b be44123g8c be44123g8a test2.tif >> Creating output file that is 11039P x 15191L. Processing input file >> be44123g8b. 0...10...20...30...40...50...60...70...80...90...100 - done. >> Processing input file be44123g8c. >> 0...10...20...30...40...50...60...70...80...90...100 - done. Processing >> input file be44123g8a. 0...10...20...30...40...50...60...70...80...90...100 >> - done. test2.tif looks fine with gdalinfo and in OpenEV. >> That works how I want. However, I have many more than 3 grids and can't >> create an output file that large. So I use vrt which has been very useful >> to me in the past: gdalwarp -t_srs "EPSG:2913" -s_srs "EPSG:2994" -srcnodata >> "0 0 0" -dstnodata "0 0 0" -of VRT be44123g8b be44123g8c be44123g8a >> test2.vrt Creating output file that is 11039P x 15191L. Processing input >> file be44123g8b. test2.vrt looks fine with gdalinfo but not in OpenEv. >> Also, when I look in the .vrt file itself, I only see one reference to the 1 >> grid and not to the other 2 grids: <SourceDataset >> relativeToVRT="1">be44123g8b</SourceDataset> >> I also notice that when processing to tif each of the 3 grids are listed. >> When processing to .vrt only 1 grid is listed. >> I read up on vrt here, http://www.gdal.org/gdal_vrttut.html to try and >> manually create/edit a vrt file but my preliminary tries weren't successful. >> Let me know if you need any additional information on this or have any >> ideas. > > Eli, > > I am afraid that gdalwarp just doesn't support producing VRTs containing > multiple source files. It would, I think, be reasonably challenging to > correct - not just a quick bug fix. You could file a ticket on it. > > You could do two steps, gdalwarp each independently to TIFF, and then > use something like gdalbuildvrt to build a mosaic vrt. Or if the source > files are all in the same coordinate system, perhaps you could build a > mosaic vrt, and then use gdalwarp to produce a corresponding warped vrt. > > I will say that this is pushing the VRT mechanism fairly far and the > efficiency of the resulting layers of vrt may not be that great.
I would simply second Frank's final comment. When using a warped vrt, your computer has to go through the computational requirements to do the warp every time you load the vrt in a GIS or spatial data viewing software. This will grow tiresome real quickly. I have tried this myself before and determined that sacrificing hard drive space was preferable to sacrificing cpu cycles repeatedly. Regards, John _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
