## DESCRIPTION

This command works only interactively. It clears the entire graphics screen and provides a graphical interaction allowing the selection of transects for which profiles are then generated. Input parameters can be specified on the command line for quicker start-up.

## USER PROMPTS

First, you will be presented with a prompt asking you to choose a raster map layer to be profiled. Then you will be prompted for an optional display raster. The optional display raster will be shown rather than the profiled raster. This is useful to be able to more easily see ground features, such as might be visible in an aerial photo or satellite image. Finally, you will be prompted for the name prefix for output file(s) containing the profile data. This is an optional feature.

After parameters are given, the raster layer will be displayed in the left half of the graphics monitor, and the right half will be divided into four frames. There will also be two frames along the top of the monitor: a mouse-button menu frame on the left, and a status frame on the right.

The mouse-button menu initially offers you three options:

  Mouse Buttons:
  Left: Where am I?
  Middle: Mark FIRST Point of Profile Line.
  Right: QUIT this.

You may query the displayed raster map layer by indicating points with the left mouse-button. The coordinates and category value of each point that you indicate will be displayed on in the status frame. If you mark the first point of the profile line you will be presented with the following mouse-button menu:

  Mouse Buttons:
  Left: Where am I?
  Middle: Mark SECOND Point of Profile Line.
  Right: QUIT this.

Once you mark the second point of the profile line, the profile line will be labeled (with a letter from A to D) and displayed in one of the four display frames on the right hand side of the screen. You will then be presented with a third mouse-button menu:

  Mouse Buttons:
  Left: DO ANOTHER
  Middle: CLEAR DISPLAY
  Right: QUIT this.

If you would like to view another profile, click on the left mouse-button. If you would like to redisplay the raster map layer and clear out the four profile frames, click on the middle mouse-button. If you would like to quit, then click on the right button.

If you selected the plotfile option, you will have up to four files starting with the name and followed by a suffix of the plot letter A, B, C, or D. The plots that are written to these files reflect the last of each plot done with that letter (i.e. They will match what's in the display when you quit).

The format of the plot files is not geared toward any particular software, but should be easy to coax into a number of other programs. The first three lines contain some header information about the plot, each prefixed with a `#` sign to denote a comment. A fourth comment line describes the data that follows. It consists of the distance (always in meters), the cell value (in whatever units it is in), the easting in decimal format, and the northing in decimal format. The number of values will vary depending on the length of the profile, cell resolution and the slope angle of the profile line. Below is an example of a plotfile:

`# Profile A of elev.ft@snows
# From (702879.29679757, 4287317.55920185) to (702722.40973589, 4287061.72632285)
# Stats: Count = 644, Min = 2424.658936, Max = 2513.246094
# dist value east north
0.000000 2513.246094 702879.102364 4287317.516912
0.000000 2513.246094 702878.713496 4287317.118970
0.556395 2513.246094 702878.324629 4287316.721029
1.112790 2513.246094 702878.324629 4287316.323088
...`

## NOTES

You might notice the first two 'dist' values in the profile output above are both zero. This is due to the fact the cell resolution for this file is less than one meter, and so the function that calculates the distance considers the distance between the first cell and the second to be zero. You might also notice, the coordinates given in the header and displayed on screen are slightly different from the first and last coordinates given in the profile data output. This is because the profile data output finds the eastings and northings for the center of the cells while the coordinate transformations from mouse clicks might yield slightly different coordinates which still fall within the same cell boundaries. The difference should always be less than the distance between the center and any corner (not edge!) of the cell at the resolution of the profiled raster.

Only four output plotfiles can be made. Each time a new profile is run, the plotfile is immediately written to the file name.letter. One can take advantage of this fact to create an unlimited number of plotfiles simply by renaming the output files before running more profiles. This may not always be the case, but it is at the time of this writing.

Useful enhancements to d.profile would include:

1. Adding an option to display profiles using category colors, like a bar-chart.
2. Allowing profile lines to be defined by a series of points, not just two.
3. Allowing profiles to be saved in a file, for later viewing by GRASS.
4. Allowing the user to enter profile line points by typing coordinates.

### Perl Script to convert output to a site_list

The script below will convert the plotfile output to the site_list format. It probably won't work 100% for lat/lon datasets.

`#! /usr/bin/perl -w
# prof2sites.pl: converts the output of d.profile to a site_list`

my ($dist, $elev, $east, $north);

while (<STDIN>)
{
if (m/^#/)
{
print "$_";
}
else
{
chomp;
($dist, $elev, $east, $north) = split / /;
print "$east|$north|$elev|#1 \%$dist \@Profile\n";
}
}

## BUGS

None known.

## AUTHOR

Dave Johnson
DBA Systems, Inc.
10560 Arrowhead Drive
Fairfax, Virginia 22030

Modified by Eric G. Miller for profile output, support of floating point rasters, and optional display raster (02-Dec-2000).

Last changed: $Date: 2003/04/11 15:07:53 $