Pentland.exe Program - Notes on use

May 6th 2003 

Revised: 23rd October 2003

M J de Smith

This program, and the Steiner.exe program, were coded by Novica Radonic. 
They are written in C++ and are not intended as 'production' software, 
simply as tests for concepts.To use: Unzip the program and sample data 
file. Double click the program in Exploere to run. The program starts up 
with a blank screen since it expects a GRD format DEM file as input - 
the sample file is of this format and can be opened with a text editor. 
This file format is used by Surfer and other programs 
(see www.goldensoftware.com for a demo copy of Surfer). 

The test file is 400x400, but other files and sizes may be used as 
long as their format is consistent with the GRD file structure.

Use the File menu to open the data file provided. If the screen shows
a random pattern of colours then your screen settings are less than 
32-bit and you will need to use the Options menu, Use Bitmap menu item
to reset the display so it looks OK, or reset your screen settings to
32-bit colour. 

To use the program simply click on a portion of the DEM and drag a line
to a second point, and release the mouse. The search will proceed and 
when complete will display a Results form. The start, end and heights 
are displayed in the status bar of the form 
during selection and on the Results form.

The Options menu allows you to change many of the settings (e.g. the 
scale use - 25 is the default, i.e. 25 metres to the DEM cell; setting
the max height difference or gradient acceptable, or the step length),
and to repeat the search process with or without the changes. 
The path results data may be saved to disk (for the optimised blue path). 

New facilities: 

(i) Gradient constraints: as part of the optimisation process gradient 
or height difference constraints may be added and paths sought which 
satisfy the constraints set. Note that it may not be possibly to find 
a solution path if the gradient constraint is too severe (low) in a 
landscape which is extremely hilly or mountainous.

(ii) Nodes and saved data: On completion of the path optimisation process
 you can opt to highlight the location of the optimised solution nodes. 
The output file (Save results... option) saves the location of the nodes,
the height of the surface at these points and the gradient. It also saves
a finer resolution version of the path between the nodes with the incremental
area above or below the landscape surface cut by the path - these differences
occur because the optimised solution path has a longer step length in general
than the underlying surface resolution. The difference is a function of the 
step length set prior to generating a solution path, and as a result of 
elimination of steps during the optimisation process. The latter seeks to 
reduce the total path length by node elimination subject to any gradient 
constraints set.

M J de S