Flags:¶

-n

Output header row

-f

Show the category labels of the grid cell(s)

-r

Output color values as RRR:GGG:BBB

-i

Output integer category values, not cell values

-c

Turn on cache reporting

-v

Show the category for vector points map

--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:¶

map=name[,name,...] [required]

Name of existing raster map(s) to query

coordinates=east,north

Coordinates for query

points=name

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

null_value=string

String representing NULL value
Default: *

output=name

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

separator=character

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

cache=integer

Size of point cache
Default: 500

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