doc: Add plots demonstrating the use of slope.py.

* doc/fullswof-utils.texi (Demos): Add sample plots.

1 files changed, 38 insertions, 7 deletions

diff --git a/doc/fullswof-utils.texi b/doc/fullswof-utils.texi
index bf39498..4e51a5e 100644
--- a/doc/fullswof-utils.texi
+++ b/doc/fullswof-utils.texi
@@ -376,13 +376,44 @@ also provided.
 
 To run the demos directly, first change the current working directory to
 the @file{demo} directory.  Then execute the individual program
-(@pxref{Invoking makeBoundary} for an example).
-
-The input files may be viewed with a text editor.  To experiment with
-the control parameters, first back up the distributed input files and
-then edit the parameter values as desired.  Note that the
-@command{makeBoundary} program will overwrite its output file if it
-already exists.
+(@pxref{Usage} for the command line syntax).
+
+The input files for @command{makeBoundary} may be viewed with a text
+editor.  To experiment with the control parameters, first back up the
+distributed input files and then edit the parameter values as desired.
+Note that the @command{makeBoundary} program will overwrite its output
+file if it already exists.
+
+Running @command{slope.py} provides an opportunity to test the effect of
+marker positioning.  Contour plots of elevation and slope are displayed
+when the @kbd{m} key is pressed.  The elevation contour plot allows the
+feature of interest to be identified.  Markers are placed in pairs on
+either side of the channel feature.  An example of a set of marker pairs
+is shown in @ref{fig:markers}.
+
+@float Figure,fig:markers
+  @center @image{./images/markers}
+  @caption{Contour plots of elevation (left) and slope (right).  Feature markers are shown as red disks.}
+@end float
+
+@command{slope.py} draws a straight line between each pair of markers.
+A search procedure reveals the position along each line at which the
+elevation is a minimum.  The set of minumum positions identifies the
+centre-line of the channel.  The profile of the channel is plotted and
+displayed when the @kbd{p} key is pressed.  The profile calculated from
+the markers shown in @ref{fig:markers} is shown in @ref{fig:profile}.
+
+@float Figure,fig:profile
+  @center @image{./images/profile}
+  @caption{Elevation plotted against distance from bottom boundary.}
+@end float
+
+The blue line in @ref{fig:profile} shows the height variation of the
+channel centre-line.  The best-fit line is shown by the dashed red line.
+The gradient of the best-fit line and the intercept on the y-axis are
+printed to standard output.  The data points that define the blue line
+are written to the file @file{1D.txt} when the @kbd{s} key is pressed.
+The file is overwritten if it already exists.
 
 @node GNU Free Documentation License, Index, Usage, Top
 @appendix GNU Free Documentation License