* Helmut Kudrnovsky <[email protected]> [2019-09-10 20:12:09 -0700]:
Rich Shepard wrote
I am downloading and importing 1m LiDAR DEMs for a 667 mi^2 (1727.5 km^2)
drainage basin. These are all in 7.5' topographic quad sections. The files
take up a lot of disk space and memory when working with them.
I assume that by careful setting of the region I can display the
individual
maps as a single map, and I can set a computational mask using the vector
basin watershed (boundary). Is there way to 'clip' the DEM using the
watershed map in the way that v.clip works with two vector maps? While the
workstation has 32G RAM and 2T of disk space I would like to limit the DEM
to the drainage basin itself and exclude all areas outside it.
Looking at all the r.* modules in core and extensions none strikes me as
the
appropriate tool.
I'm open to advice on working with huge raster files.
Regards,
Rich
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To save diskspace,, build a virtual raster with your tiles outside GRASS by
GDAL's buildvrt, do r.external yourvirtual.vrt.
No import is needed for raster calculations, r.external to link the virtual
raster works nicely..
If there is no need for a GDAL VRT, then, alternatively, link all tiles
as pseudo-raster maps in GRASS GIS' data base, of course using
`r.external`. Then, build a GRASS GIS virtual raster data set using
`r.buildvrt`. Clipping or "extracting" parts of this VRT will expectedly
work.
Nikos
regarding to clip a raster to vector extent, there a several ways. One may
be: g.region -a raster=yourraster vector=yourvector followed by a r.mask
vector=yourvector then r.mapcal clippedraster=yourraster
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