## NAME

r.what

## 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 400.

## SEE ALSO

d.where, 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

Last changed: $Date: 2010-09-16 09:25:59 +0200 (Thu, 16 Sep 2010) $

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