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Re: hacheurs


Russell Towle wrote:
> 
> Hi all,
> 
> Recent discussion of "waterfall plots" prompts me to pose a somewhat
> related query. I work with digital elevation model data sets from the
> U.S.G.S. to produce contour maps, using ListContourPlot under
> Mathematica 2.2. I would like to be able to produce old-style
> quasi-contour maps using "hacheurs," in which the contours themselves
> are not drawn, but instead, line segments at right angles to the
> contour lines, of lengths inversely proportional to steepness of slope
> (short hacheurs->steep slope). Any ideas?
> 
> 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
> ------------------------------

One possibility might be to use the lists of {x,y,z} to create an
InterpolatingFunction for z = f(x,y). Then (I think) you'd want to plot
the vector field 1/|gradient|^2*gradient, possibly offset if you want
these centered on the contour lines rather than emanating therefrom.

Daniel Lichtblau
Wolfram Research


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