r.what(1)

NAME
r.what - Queries raster map layers on their category values and category labels.

KEYWORDS
raster

SYNOPSIS
r.what
r.what help
r.what [-fci] input=string[,string,...] [cache=integer] [null=string] [east_north=east,north[,east,north,...]]

  Flags:

-f  Show the category label in the grid cell(s)

-c  Turn on cache reporting

-i  Output integer category values, not cell values

  Parameters:

input=string[,string,...]
    Name of existing raster map(s) to query

cache=integer
    Size of point cache Default: 500

null=string
    Char string to represent no data cell Default: *

east_north=east,north[,east,north,...]
    Coordinates for query

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, or redirected via stdin from an input text file, script, or piped from another program (like d.where).

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 from stdin on the command line
Input coordinates may be given directly from stdin, for example:
 (input data appears between the "EOF" markers)
r.what input=soils,aspect << EOF
635342.21 7654321.09 site 1
653324.88 7563412.42 site 2
EOF
635342.21|7654321.09|site 1|45|21
653324.88|7563412.42|site 2|44|20
echo "635342.21 7654321.09" | r.what input=soils,aspect
635342.21|7654321.09|45|21

  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 coordinates and labels given in the example above:
r.what input=soils,aspect < input_coord.txt
635342.21|7654321.09|site 1|45|21
653324.88|7563412.42|site 2|44|20

  Input coordinates given as a module option
The module's east_north 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).
r.what input=soils,aspect east_north=635342.21,7654321.09,653324.88,7563412.42
635342.21|7654321.09|45|21
653324.88|7563412.42|44|20

  Input coordinates piped from another program
The input coordinates may be "piped" from the stdout of another program. For example:
d.where | r.what input=soils,aspect
635342.21|7654321.09|45|21
653324.88|7563412.42|44|20
In the next example, vector point coordinates are piped from the v.out.ascii module . The standard UNIX program "tr" is used to convert the column separators in v.out.ascii's output into spaces for r.what.
v.out.ascii bugsites fs=' ' | r.what input=soils,aspect

  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 input=soils,aspect << EOF
635342.21 7654321.09 site 1
653324.88 7563412.42 site 2
EOF
635342.21|7654321.09|site 1|45|NaC|21|30 degrees NW
653324.88|7563412.42|site 2|44|NdC|20|15 degrees NW

NOTE
The maximum number of raster map layers that can be queried at one time is 150.

SEE ALSO
d.where, r.cats, 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

Last changed: $Date: 2007/03/23 22:54:16 $

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