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MathGroup Archive 1998

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more and more hacheurs

  • To: mathgroup at smc.vnet.net
  • Subject: [mg12677] more and more hacheurs
  • From: Russell Towle <rustybel at foothill.net>
  • Date: Mon, 1 Jun 1998 23:16:49 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

The problem of creating hacheurs I posted recently can be made more
specific:

1. How to work with the contour lines created by ListContourPlot? They
do not seem to exist as grouped objects, like polygons do in Graphics3D
polyhedra. If converted to Graphics objects, how to associate their
elevations with them?

2. Suppose we have obtained a single contour line. We wish to draw
little line segments (hacheurs) at right angles, evenly spaced along
the contour. How to get these evenly spaced points?

3. The lengths of these little segments must be made to depend upon the
distance to contiguous contour lines, above and below the reference
elevation... So if we are placing hacheurs on the 3200 foot contour,
contour intervals 40 feet, we need to find the 3200 foot contour, as
well as the 3160 foot and 3240 foot contours.

4. Finally, when the slope of the surface gets fairly flat, below a
user-defined angle, we forego the drawing of hacheurs at all.

So all in all a Hacheurs funtion would operate upon a ListContourPlot
object, with additional arguments being a "minimum slope" below which
no harcheurs are drawn, and possibly a "magnitude argument" in which
the lengths of the hacheurs segments can be modified, and possibly a
"style sheet" argument, in which the hacheurs could be assigned colors,
thicknesses, etc.

Russell Towle
Giant Gap Press:  books on California history, digital topographic maps
P.O. Box 141
Dutch Flat, California 95714
------------------------------
Voice:  (916) 389-2872
e-mail:  rustybel at foothill.net
------------------------------



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