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.
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.
Update: I found the 10m DEMs to replace the ones I lost when a disk failed.
The lower resolution DEMs are better suited to such a large drainage basin,
but the rest of my questions remail valid.
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
_______________________________________________
grass-user mailing list
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..
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
* Helmut Kudrnovsky <hellik@web.de> [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
_______________________________________________
grass-user mailing list
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
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..
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
Helmut,
This is exceptionally useful information. I've not looked closely at gdal
and don't know all its capabilities. Perhaps this could be added to the Wiki
as it's likely to be useful to others.
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,
I've insufficient experience to know whether there is need for GDAL VRT. But
I'll look closely at what you and Helmut advise and gain some experience.