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Newsgroups: info.grass.user
Path: zorro.cecer.army.mil!shapiro
From: shapiro at zorro.cecer.army.mil (Michael Shapiro)
Subject: Re: rasterizing digitized contour maps
Message-ID: <C3I6Ko.99y at news.cecer.army.mil>
Sender: news at news.cecer.army.mil (Net.Noise owner)
Organization: US Army Corps of Engineers Construction Engineering Research Labs
References: <9302251602.AA01823 at cotopaxi.hwr.arizona.edu>
Date: Sun, 7 Mar 1993 05:14:48 GMT
Lines: 39

In <9302251602.AA01823 at cotopaxi.hwr.arizona.edu> bobh at hwr.arizona.edu (Bob Harrington) writes:

r.surf.idw or r.sruf.idw2 use inverse-distance-squared weights to form
average elevation. Generaly this a NOT a good method for surface generation.
These tools are much faster than those in 3.1. No telling how long, but
they take their time. You should expore the new s.sruf.tps which has
a superior model for DEMs from point data.

>I imagine some of you have done this before:

>I have a digitized contour map that I want
>to turn into a DEM. I rasterized the contours
>with v.to.rast, which worked fine, and now want 
>to interpolate all the cells between the contours.

>I am trying to use r.surf.idw2 to do this,
>but I have two questions:

>1. Is this the best way to do this? I expect
>some strange results using r.surf.idw2, because
>for cells near a contour, all the nearest cells
>used in the interpolation will have the same
>value, so the interpolated cell will just be 
>assigned the same value as the nearby contour.

>2. I launched r.surf.idw2 yesterday on a SPARC 10,
>and it is still working this morning. The map is
>834 by 989. How long is this going to take? 

>Cheers,

>Bob Harrington
>Hydrology and Water Resources
>University of Arizona
-- 


Michael Shapiro U.S. Army CERL
Environmental Division