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r.what(1grass) GRASS GIS User's Manual r.what(1grass)

NAME

r.what - Queries raster maps on their category values and category labels.

KEYWORDS

raster, querying, position

SYNOPSIS

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]

Flags:


Output header row

Show the category labels of the grid cell(s)

Output color values as RRR:GGG:BBB

Output integer category values, not cell values

Turn on cache reporting

Show the category for vector points map

Allow output files to overwrite existing files

Print usage summary

Verbose module output

Quiet module output

Force launching GUI dialog

Parameters:


Name of existing raster map(s) to query

Coordinates for query

Name of vector points map for query
Or data source for direct OGR access

String representing NULL value
Default: *

Name for output file (if omitted or "-" output to stdout)

Field separator
Special characters: pipe, comma, space, tab, newline
Default: pipe

Size of point cache
Default: 500

DESCRIPTION

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.

EXAMPLES

Input coordinates given as an option

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

Input coordinates given as a vector points map

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
...

Input coordinates given as a vector points map with cats

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
...

Input coordinates given as a vector points map, output into CSV file

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 ...

Input from a text file containing coordinates

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 from standard input on the command line

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

Input coordinates piped from another program

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
...

Output containing raster map category labels

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

NOTE

The maximum number of raster map layers that can be queried at one time is 400.

TODO

Fix 400 maps limit

SEE ALSO

r.category, r.report, r.stats, r.series, r.univar, v.what, v.what.rast, v.what.vect

AUTHOR

Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
Vector point input added by Martin Landa, Czech Technical University in Prague, Czech Republic

SOURCE CODE

Available at: r.what source code (history)

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© 2003-2021 GRASS Development Team, GRASS GIS 7.8.6 Reference Manual

GRASS 7.8.6