I have an area of interest that is split across two UTM zones. My desired end result is a single stitched, clipped, and re-projected image in a local coordinate system.
My usual workflow is to build a VRT that contain only the input tiles that touch the area of interest. Normally that works great, but not when split across zones. I know it's possible to create a VRT containing two or more coordinate systems with the gdalbuildvrt -allow_projection_difference option. There are at least two ways I could proceed: A) Two steps: reproject all input tiles to a common base with gdalwarp, then stitch/clip with gdalwarp -t_srs "EPSG:7645" -cutline clip.shp -crop_to_cutline aoi.vrt output.tif (where aoi.vrt contains a list of tiles that touch the AOI) B) One step: gdalwarp -t_srs "EPSG:7645" mixed_utm_zones.vrt output.tif "B" is nice option in theory. However, in my experiments, it appears that only half the AOI is processed when I try. Option "A" works fine, but it seems like the image would be resampled twice... once for each gdalwarp command? Can anyone confirm if B is theoretically possible? Better approaches? This must be a common issue. Thanks for advice! ---------------------------------------------- Jim Lacy Wisconsin State Cartographer's Office University of Wisconsin-Madison (608) 262-6850 www.sco.wisc.edu<http://www.sco.wisc.edu/> My calendar: http://go.wisc.edu/xziys4
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