[GRASS-user] Creating a ground water from a vector files of contours?

[Dylan Beaudette]

Hi Bob,

Glad to hear you are closer to a solution. v.surf.rst *should* be able to use 
contour data (referred to as isoline data in the manual). it sounds like your 
contours were imported as polygons, which would result in centroids being 
present. 

Either re-import your data as lines, or convert to lines. I am not sure that 
converting areas to lines will preserve the connection between contour and 
elevation attribute. Perhaps others on the list can provide some feedback on 
this. For starters post the results of :
v.info your_contour_vector 

Alternatively, as Hamish suggested you might try out r.surf.contour -- note 
that this does not use the RST interpolator and has some limitation with 
respect to NULL values. Also it only produces integer grids.

Cheers,

Dylan



On Tuesday 06 February 2007 15:23, Moskovitz, Bob wrote:
> Hi Dylan,
>
> Looks like I was asking the computer to eat more then it can chew :-)  I
> have tried a smaller area and v.surf.rst did finish in good time.  Now I
> have another problem.  v.surf.rst seem to ignore the contours, but it
> noticed the centroids.  I see a bunch of bulls-eyes all over my map.  I
> guess I have missed a step?
>
> Bob
>
> -----Original Message-----
> From: Dylan Beaudette [mailto:dylan.beaudette at gmail.com]
> Sent: Monday, February 05, 2007 1:39 PM
> To: grassuser at grass.itc.it
> Cc: Moskovitz, Bob
> Subject: Re: [GRASS-user] Creating a ground water from a vector files of
> contours?
>
>
> Hi Bob,
>
> What have you defined your region as: i.e. what is the cell size, and what
> sort of area are you dealing with? If the cell size is too small, or your
> have defined a very large area, then v.surf.rst will take a very long time
> -- possibly producing a finer grid than really needed.
>
> That aside, contour data can sometimes be a troublesome source for an
> interpolation. Also, for VERY large datasets (small resolution / large
> area) you might try some other interpolator. check the archives for some
> ideas.
>
> Cheers,
>
> Dylan
>
> On Monday 05 February 2007 12:50, Moskovitz, Bob wrote:
> > Hello Grassusers,
> >
> > Like the subject line says, I need help creating a ground water map using
> > a vector file of contours.  The ground water file came from a E00 file
> > that was read into Grass using v.in.e00.  I am currently running
> > v.surf.rst which is taking a long time to run.  Are there other ways to
> > do this problem?
> >
> > Thanks in advance,
> > Bob
> >
> > Bob Moskovitz
> > Seismic Hazards Zonation Program
> > California Geological Survey
> > http://gmw.consrv.ca.gov/shmp
> >
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-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341