* Markus Metz <[email protected]> [2018-06-04 14:37:41 +0200]:
A new GRASS virtual raster format has been added to trunk in r72761-4, together with a new module to build a GRASS VRT: r.buildvrt. *r.buildvrt* builds a virtual raster (VRT) that is a mosaic of the list of input raster maps. The purpose of such a VRT is to provide fast access to small subsets of the VRT, also with multiple simultaneous read requests. *r.buildvrt* creates a list of raster maps that can be located in different mapsets. The ouput is a read-only link to the original raster maps which is only valid if the original raster maps remain in the originally indicated mapset. A VRT can also be built from raster maps registered with *r.external*. Reading the whole VRT is slower than reading the equivalent single raster map. Only reading small parts of the VRT provides a performance benefit. Please test! Markus M
Speechless! Respect Mr. Metz. A working test: # get extents g.region -ec raster=L5192028_02820090723_Rad_ref_TRC_BYTE_FROMGLCaggV1@PERMANENT res=1000 north-south extent: 214230.000000 east-west extent: 246330.000000 center easting: 741150.000000 center northing: 5100000.000000 # set east to center easting of landcover map g.region -a e=738150.000000 res=1000 # build a "half" map r.mapcalc "WestHalf = 1" --o # set west to center easting of land cover map, reset east g.region w=738150.000000 e=$(echo "246330/2 + 741150" |bc) res=1000 -a # build other half r.mapcalc "EastHalf = 2" --o # combine r.buildvrt input=WestHalf,EastHalf out=fIRSTgRASSYvRT --o title="First GRASS GIS Virtual Raster Map" # ? r.info -ge fIRSTgRASSYvRT north=5208000 south=4992000 east=865000 west=617000 nsres=1000 ewres=1000 rows=216 cols=248 cells=53568 datatype=CELL ncats=0 map=fIRSTgRASSYvRT mapset=lst location=lst_time_series database=/geo37/grassdb date="Mon Jun 4 16:02:58 2018" creator="nik" title="First GRASS GIS Virtual Raster Map" timestamp="none" units="none" vdatum="none" source1="" source2="" description="generated by r.buildvrt" comments="r.buildvrt --overwrite input="WestHalf,EastHalf" output="fIRSTgRASSY\vRT" title="First GRASS GIS Virtual Raster Map"" # see in-terminal g.region -a raster=L5192028_02820090723_Rad_ref_TRC_BYTE_FROMGLCaggV1@PERMANENT res=1000 ty.d.rast fIRSTgRASSYvRT # terminology's `tycat` Thank you so very much Markus, Nikos
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