[GRASS-user] How to create polygon from two selected contour line

[Michael Barton]

The trick for many things in GRASS is to "think raster" instead of thinking vector.

Make a raster DEM from your map (if you don't already have one). 

Query the raster (e.g., with r.mapcalc or r.reclass) to create a raster of elevations between your contour lines (e.g., in r.reclass the specification 1000 thru 1500 = 1). 

Run r.to.vect on the queried map to turn it into an area.

Michael



On Feb 25, 2012, at 10:00 AM, <grass-user-request at lists.osgeo.org> <grass-user-request at lists.osgeo.org> wrote:

> Date: Sat, 25 Feb 2012 10:42:20 +0200
> From: Maris Nartiss <maris.gis at gmail.com>
> Subject: Re: [GRASS-user] How to create polygon from two selected
> 	contour line
> To: Paolo Cavallini <cavallini at faunalia.it>
> Cc: grass-user at lists.osgeo.org
> Message-ID:
> 	<CAK8GbeCR-5p7QnTp6cQDLT16pZ=yMbrdsqPaT73d+cZbVWQTKQ at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
> 
> Convert line type from line to boundary (v.type)
> Digitize a pair of new boundaries between both contour lines to form a
> enclosed area or use v.hull to get an outline for merging in (v.patch)
> Add a centroid (digitize or v.centroids) to enclosed area.
> Profit!
> 
> Not the mos easy way, still possible.
> 
> Maris.
> 
> 2012/2/25 Paolo Cavallini <cavallini at faunalia.it>:
>> Il 25/02/2012 08:45, SWAPAN GHOSH ha scritto:
>> 
>>> Hello Grassuser,
>>> Anybody can please help me " To create polygon from two selected contour
>>> line " using grass comand..........
>> 
>> I'm afraid I can't - I tried recently, no joy.
>> Good luck, if you succeed please let us know.
>> All the best.
>> 
>> --
>> Paolo Cavallini
>> See: http://www.faunalia.it/pc
>> 
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> 

_____________________
C. Michael Barton
Visiting Scientist, Integrated Science Program
National Center for Atmospheric Research &
University Consortium for Atmospheric Research
303-497-2889 (voice)

Director, Center for Social Dynamics & Complexity 
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu