r.buildvrt.gdal.py - GRASS manual

NAME

r.buildvrt.gdal.py - Build GDAL Virtual Rasters (VRT) over GRASS GIS raster maps

KEYWORDS

SYNOPSIS

r.buildvrt.gdal.py

r.buildvrt.gdal.py --help

r.buildvrt.gdal.py [-mr] [input=name[,name,...]] [file=name] [vrt_directory=name] output=name [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-m: Read data range from metadata; WARNING: metadata are sometimes approximations with wrong data range
-r: Create fast link without data range; WARNING: some modules do not work correctly without known data range
--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

input=name[,name,...]: Name of input raster map(s)
file=name: Name of input file
vrt_directory=name: Directory to store GDAL VRT files in. Default is: $GISDBASE/$PROJECT/$MAPSET/gdal
output=name [required]: Name for output raster map

DESCRIPTION
REQUIREMENTS
EXAMPLES
SEE ALSO
AUTHORS

DESCRIPTION

r.buildvrt.gdal builds GDAL virtual rasters over GRASS GIS raster maps and links them to the mapset with r.external. The module is written as a workaround for a limitation in GRASS GIS Virtual Rasters (VRT) format with GDAL-linked raster maps (through r.external / r.external.out. In that case GRASS GIS Virtual Rasters currently show performance issues. See: #4345

For the resulting maps GDAL VRT text files are created either in a directory named "gdal" in the current mapset or in a user-defined vrt_directory. Those files are not removed when the raster map is removed and the user is responsible for removing them when needed.

REQUIREMENTS

r.buildvrt.gdal uses the Python bindings for GDAL and requires the GDAL-GRASS driver to include raster maps in native GRASS format in GDAL VRTs.

EXAMPLES

# Create external example data
regs='s,0,1000
n,500,1500'

eval `g.gisenv`
external_path="${GISDBASE}/${LOCATION}/${MAPSET}/.tmp/vrt"
mkdir -p "$external_path"
for reg in $regs
do
  r=$(echo $reg | cut -f1 -d",")
  s=$(echo $reg | cut -f2 -d",")
  n=$(echo $reg | cut -f3 -d",")

  g.region -g n=$n s=$s w=0 e=1000 res=1
  r.external.out format=GTiff options="compress=LZW,PREDICTOR=3" \
    directory="$external_path"
  r.mapcalc --o --v expression="${r}_${s}_gtiff_ntfs=float(x()*y())"
done

# Run performance tests
g.region -g n=1500 s=0 w=0 e=1000 res=1
format_type=gtiff_ntfs
rmaps=$(g.list type=raster pattern="*_*_${format_type}", sep=",")

# Using GRASS GIS VRT
r.buildvrt --o --v input="$rmaps" output=vrt_${format_type}
time r.univar map=vrt_${format_type}

# Using GDAL VRT
r.buildvrt.gdal --o --v input="$rmaps" output=vrt_${format_type}_gdal
time r.univar map=vrt_${format_type}_gdal

AUTHORS

Stefan Blumentrath

SOURCE CODE

Available at: r.buildvrt.gdal source code (history)

Latest change: Thursday Feb 20 13:02:26 2025 in commit: 53de8196a10ba5a8a9121898ce87861d227137e3