Hi Andy, Yep, that was it. I didn't know QGIS could do that; another good example of software trying to be "smart" and confusing the poor user. :-)
==== I didn't know gdalwarp could do mosaicing too. I'll have to test it. I'll ask on the gdal list if I want to try the -setci parameter. Many thanks! Jonathan On 2 December 2013 15:48, Andrew Harfoot <a...@geodata.soton.ac.uk> wrote: > PS. gdalwarp offers more flexibility when mosaicing rasters, and is > better at memory management. I have just noticed that in GDAL 1.10 and > above there is an gdalwarp option -setci that 'Sets the color > interpretation of the bands of the target dataset from the source dataset'. > This could be used to remove the assignment of the alpha channel to the IR > band on merging. Sadly there isn't an example of its usage! > > > Cheers, > > Andy > > On 02/12/2013 11:53, Jonathan Moules wrote: > > Hi List, > I've got a 4 band raster aerial photography (RGBI) that comprises lots of > tiles. I've merged some of the tiles together with: > > gdal_merge -o 1.tif -of GTiff -co TILED=YES -co BIGTIFF=YES -co >> COMPRESS=JPEG -co JPEG_QUALITY=50 -co BLOCKXSIZE=512 -co BLOCKYSIZE=512 >> --optfile tiff_list.txt > > > But the resultant file looks funny in QGIS. > This is what the source file looks like (correct): > [image: Inline images 1] > > This is what the merged file looks like (wrong): > [image: Inline images 2] > > All the shadows are a whitey colour. This doesn't happen with 3-band > (RGB) images. > I've tried comparing individual bands; they all look different in the > 4-band. > > However, if I open the four-band in ArcGIS, it looks fine (both source > and original). > > Anyone know what's going on? Is it a QGIS bug or is it doing something > "smart"; I can't see anything odd going on with symbology. > > Thanks, > Jonathan > > This transmission is intended for the named addressee(s) only and may > contain sensitive or protectively marked material up to RESTRICTED and > should be handled accordingly. Unless you are the named addressee (or > authorised to receive it for the addressee) you may not copy or use it, or > disclose it to anyone else. If you have received this transmission in error > please notify the sender immediately. All email traffic sent to or from us, > including without limitation all GCSX traffic, may be subject to recording > and/or monitoring in accordance with relevant legislation. > > _______________________________________________ > Qgis-user mailing > listQgis-user@lists.osgeo.orghttp://lists.osgeo.org/mailman/listinfo/qgis-user > > > > -- > Andy Harfoot > > GeoData Institute > University of Southampton > Southampton > SO17 1BJ > > Tel: +44 (0)23 8059 2719 > Fax: +44 (0)23 8059 2849 > www.geodata.soton.ac.uk > > > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/qgis-user > -- This transmission is intended for the named addressee(s) only and may contain sensitive or protectively marked material up to RESTRICTED and should be handled accordingly. Unless you are the named addressee (or authorised to receive it for the addressee) you may not copy or use it, or disclose it to anyone else. If you have received this transmission in error please notify the sender immediately. All email traffic sent to or from us, including without limitation all GCSX traffic, may be subject to recording and/or monitoring in accordance with relevant legislation.
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