## DESCRIPTION

This program outputs two or four column (with -g) data to stdout or an ASCII file. The default two column output consists of cumulative profile length and raster value. The optional four column output consists of easting, northing, cumulative profile length, and raster value. Profile end or "turning" points can be set manually with the coordinates argument. The profile resolution, or distance between profile points, is obtained from the current region resolution, or can be manually set with the resolution argument.

The coordinates parameter can be set to comma separated geographic coordinates for profile line endpoints. Alternatively the coordinate pairs can be piped from the text file specified by file option, or if set to "-", from `stdin`. In these cases the coordinate pairs should be given one comma separated pair per line.

The resolution parameter sets the distance between each profile point (resolution). The resolution must be provided in GRASS database units (i.e. decimal degrees for Lat Long databases and meters for UTM). By default r.profile uses the resolution of the current GRASS region.

The null parameter can optionally be set to change the character string representing null values.

## OUTPUT FORMAT

The multi column output from r.profile is intended for easy use in other programs. The output can be piped (|) directly into other programs or saved to a file for later use. Output with geographic coordinates (-g) is compatible with v.in.ascii and can be piped direcly into this program.

    r.profile -g input=elevation coordinates=... | v.in.ascii output=elevation_profile separator=space

The 2 column output is compatible with most plotting programs.

The optional RGB output provides the associated GRASS colour value for each profile point.

Option units enables to set units of the profile length output. If the units are not specified, current location units will be used. In case of geographic locations (latitude/longitude), meters are used as default unit.

## NOTES

The profile resolution is measured exactly from the supplied end or "turning" point along the profile. The end of a profile segment will be an exact multiple of the profile resolution and will therefore not always match the end point coordinates entered for the segmanet.

To extract the numbers in scripts, following parameters can be used:

    r.profile input=dgm12.5 coordinates=3570631,5763556 2>/dev/null

This filters out the everything except the numbers.

## EXAMPLES

### Extraction of values along profile defined by coordinates (variant 1)

Extract a profile with coordinates (wayoints) provided on the command line (North Carolina data set):

    g.region raster=elevation -p
    r.profile -g input=elevation output=profile_points.csv \
              coordinates=641712,226095,641546,224138,641546,222048,641049,221186

This will extract a profile along the track defined by the three coordinate pairs. The output file "profile_points.csv" contains east,north,distance,value (here: elevation).

### Extraction of values along profile defined by coordinates (variant 2)

Coordinate pairs can also being "piped" into r.profile (variant 2a):

    r.profile elevation resolution=1000 file=- << EOF
    641712,226095
    641546,224138
    641546,222048
    641049,221186
    EOF

Coordinate pairs can also being "piped" into r.profile (variant 2b):

    echo "641712,226095
    641546,224138
    641546,222048
    641049,221186" > coors.txt
    cat coors.txt | r.profile elevation resolution=1000 file=-

The output is printed into the terminal (unless the output parameter is used) and looks as follows:

    Using resolution: 1000 [meters]
    Output columns:
    Along track dist. [meters], Elevation
    Approx. transect length: 1964.027749 [meters]
     0.000000 84.661507
     1000.000000 98.179062
    Approx. transect length: 2090.000000 [meters]
     1964.027749 83.638138
     2964.027749 89.141029
     3964.027749 78.497757
    Approx. transect length: 995.014070 [meters]
     4054.027749 73.988029

## SEE ALSO

v.in.ascii, r.what, r.transect, wxGUI profile tool

## AUTHOR

Bob Covill