[Freegis-list] ANN: polygon based map contouring routine for delphi 5

[Alexander Weidauer]

Hi folks,

I want to announce a source code free  map contouring routine
witch delivers polygon strikes for each intersection height.

The original contouring routine was published in germany 1987 by
Markus Weber Turbopascal ToolsPractical usage of "Turbo Pascal in
nature science" and I adopt it in 1990 for general use from
the third edition of these book ISBN-3-528-24543-3.

The basic idea of the algorithm is the desciption of the movement of
an unintelligent mouse in a labyrinth with clockwise spin if the move
fails and a counter clock wise spin if the move succeeds for
the next exploring direction.
Versus the contouring other authors like of Paul. D. Brouke
it delivers open or closed polygons (rings) and it is possible to
create faces over on height intersection plane.
To build a DEM or body of heigth lines the algorithm
will take more than height intersections and therefore
more computational power.

In technical terms of the time the routine was
implemented as a direct drawing routine to the,
in recent considerations, low resoluted PC DOS screen.
I extract the these parts from the routine and try to
make it industial hard, to check border conditions, uniqe
existence polygons of each height intersected part.

it can be found at http://www.triplexware.huckfinn.de/contweber.html

The examples are very simple. It is possible to handle height fields as
well to classify pixels. The oversampling of the images is not the
best solution to prevent range errors but it still works.

Have fun Alexander Weidauer