r.what(1grass) | GRASS GIS User's Manual | r.what(1grass) |
r.what - Queries raster maps on their category values and category labels.
raster, querying, position
r.what
r.what --help
r.what [-nfricv] map=name[,name,...]
[coordinates=east,north] [points=name]
[null_value=string] [output=name]
[separator=character] [cache=integer]
[--overwrite] [--help] [--verbose] [--quiet]
[--ui]
r.what outputs the category values and (optionally) the category labels associated with user-specified locations on raster input map(s). Locations are specified as geographic x,y coordinate pairs (i.e., pair of eastings and northings); the user can also (optionally) associate a label with each location.
The input coordinates can be entered directly on the command line via coordinates parameter, or redirected via stdin from an input text file, script, or piped from another program (like v.out.ascii). Coordinates can be given also as a vector points map (points).
If none of the above input methods are used and the module is run from the terminal prompt, the program will interactively query the user for point locations and labels.
Each line of the input consists of an easting, a northing, and an optional label, which are separated by spaces. In interactive mode, the word "end" must be typed after the last pair of input coordinates.
r.what output consists of the input geographic location and label, and, for each user-named raster map layer, the category value, and (if the -f label flag is specified) the category label associated with the cell(s) at this geographic location.
The module’s coordinates parameter can be used to
enter coordinate pairs directly. The maximum number of pairs will be limited
by your system’s maximum input line length (e.g. 4096 characters).
g.region raster=landuse96_28m,aspect -p r.what map=landuse96_28m,aspect coordinates=633614.08,224125.12,632972.36,225382.87 -f 633614.08|224125.12||2|Low Intensity Developed|209.5939|209 degrees ccw from east 632972.36|225382.87||15|Southern Yellow Pine|140.7571|140 degrees ccw from east
Coordinates can be read from existing vector points map by
specifying points option. Other features than points or centroids are
ignored. Example: query North Carolina county number for each community
college:
g.region raster=boundary_county_500m -p r.what map=boundary_county_500m points=comm_colleges 145096.859150|154534.264884||39 616341.437150|146049.750884||51 ...
Coordinates can be read from existing vector points map by
specifying points option. Other features than points or centroids are
ignored. Using the v flag you can get also the cat for each feature.
Example: query North Carolina county number for each community college:
g.region raster=boundary_county_500m -p r.what map=boundary_county_500m points=comm_colleges -v 1|145096.859150|154534.264884||39 2|616341.437150|146049.750884||51 ...
Coordinates can be read from existing vector points map by
specifying points option. Other features than points or centroids are
ignored. The output is stored in a CSV file including header row. Example:
query North Carolina county number for each community college:
g.region raster=boundary_county_500m -p r.what map=boundary_county_500m points=comm_colleges \
separator=comma output=result.csv -n cat result.csv easting,northing,site_name,boundary_county_500m 145096.859150,154534.264884,,39 616341.437150,146049.750884,,51 410595.719150,174301.828884,,71 ...
The contents of an ASCII text file can be redirected to
r.what as follows. If we have a file called input_coord.txt
containing the whitespace separated coordinates and optionally labels, the
resulting raster map values are extracted:
cat input_coord.txt 633614.08 224125.12 site 1 632972.36 225382.87 site 2 r.what map=landuse96_28m,aspect < input_coord.txt 633614.08|224125.12|site 1|2|209.5939 632972.36|225382.87|site 2|15|140.7571
Input coordinates may be given directly from standard input
(stdin), for example (input data appears between the "EOF"
markers):
r.what map=landuse96_28m,aspect << EOF 633614.08 224125.12 site 1 632972.36 225382.87 site 2 EOF 633614.08|224125.12|site 1|2|209.5939 632972.36|225382.87|site 2|15|140.7571
echo "633614.08 224125.12" | r.what map=landuse96_28m,aspect 633614.08|224125.12||2|209.5939
The input coordinates may be "piped" from the standard
output (stdout) of another program. In the next example, vector point
coordinates are piped from the v.out.ascii module.
v.out.ascii comm_colleges separator=space | r.what map=boundary_county_500m 145096.8591495|154534.26488388|1|39 616341.4371495|146049.75088388|2|51 410595.7191495|174301.82888388|3|71 ...
Here we use the -f label flag to enable the output of
category labels associated with the raster cell(s), as well as values
(categorical maps only).
r.what -f map=landuse96_28m,aspect << EOF 633614.08 224125.12 site 1 632972.36 225382.87 site 2 EOF 633614.08|224125.12|site 1|2|Low Intensity Developed|209.5939|209 degrees ccw from east 632972.36|225382.87|site 2|15|Southern Yellow Pine|140.7571|140 degrees ccw from east
The maximum number of raster map layers that can be queried at one time is 400.
r.category, r.report, r.stats, r.series, r.univar, v.what, v.what.rast, v.what.vect
Michael Shapiro, U.S. Army Construction Engineering Research
Laboratory
Vector point input added by Martin Landa, Czech Technical University in
Prague, Czech Republic
Available at: r.what source code (history)
Accessed: Sunday Jan 22 07:36:42 2023
Main index | Raster index | Topics index | Keywords index | Graphical index | Full index
© 2003-2023 GRASS Development Team, GRASS GIS 8.2.1 Reference Manual
GRASS 8.2.1 |