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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:
       -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

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

       Last changed: $Date: 2017-05-16 16:04:44 +0200 (Tue, 16 May 2017) $

SOURCE CODE

       Available at: r.what source code (history)

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       © 2003-2018 GRASS Development Team, GRASS GIS 7.4.0 Reference Manual