Hi grass-users,
I'm having some difficultly patching together some raster layers (OS OpenData District Raster - TIFF). Individually, the tiles display correctly using d.rast. However, if I patch them into a single tile using r.patch, the colour for all but the first becomes mangled. Example patching two layers (left and right):
The only reference on the UG I've found is thread:
http://lists.osgeo.org/pipermail/grass-user/1998-January/001017.html
The issue seems to be something to do with colour tables in the TIFFs being different. I've not tried the solution provided, as it appears clunky and I was hoping some progress had been made since '98!
r.in.wms seems to do something like this, patching together tiles downloaded from a WMS server. I've taken a look at the code for this, but found it difficult to pick out what is relevant. There is some mention to using r.mapcalc in a similar way, and also to the GDAL script gdal_merge.py, which I've not managed to get anything sensible from.
Ideally I'd like to be able to handle these layers from within GRASS (using pre-existing commands, or a python script) rather than externally (like gdal_merge.py seems to do), although at this point I'll take whatever I can get. Can anyone suggest a way forward in this?
Also, as a more general question, does anyone have experience using the OS OpenData dataset? I'm curious to see what people have done with it since its release.
Thanks in advance,
Josh.