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Path: utzoo!linus!decvax!ittvax!dcdwest!sdcsvax!bmcg!cepu!hao!newkirk
From: newkirk@hao.UUCP
Newsgroups: net.math,net.wanted
Subject: Ridge line locator wanted
Message-ID: <1055@hao.UUCP>
Date: Tue, 10-Jul-84 15:12:42 EDT
Article-I.D.: hao.1055
Posted: Tue Jul 10 15:12:42 1984
Date-Received: Thu, 12-Jul-84 01:19:16 EDT
Organization: High Altitude Obs./NCAR, Boulder CO
Lines: 21

What is desired is, given a regular function z(x,y) specified at
uniform grid points in x and y, to locate the ridge lines in z
with a specified spatial resolution.  To put it into a geographical
term, one wants a program to find the continental divide on a 
contour map.
 
Examination of the problem shows that such "divides" are a special
set of the flow lines which are always normal to the contour lines.
Their special characteristic is that a divide connects peaks through
a saddle point.
 
I have tried at our local sources, the USGS, etc. without success
although there do exist some of the components which could be put
together a program to do this job.  Any ideas as to how to locate
if one already exists?
 
Please reply by mail as I do not normally read news.

Thanks,
Gordon Newkirk
hao!newkirk