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

GRASS GRASS user
1

Hi Dylan,

Looks like I was asking the computer to eat more then it can chew :slight_smile: 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@gmail.com]
Sent: Monday, February 05, 2007 1:39 PM
To: grassuser@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

CONFIDENTIALITY NOTICE: This communication is intended only for the use of
the individual or entity to which it is addressed. This message contains
information from the State of California, California Geological Survey,
which may be privileged, confidential and exempt from disclosure under
applicable law, including the Electronic Communications Privacy Act. If the
reader of this communication is not the intended recipient, you are hereby
notified that any dissemination, distribution, or copying of this
communication is strictly prohibited.

--
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341

2

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 :slight_smile: 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@gmail.com]
Sent: Monday, February 05, 2007 1:39 PM
To: grassuser@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
>
> CONFIDENTIALITY NOTICE: This communication is intended only for the use
> of the individual or entity to which it is addressed. This message
> contains information from the State of California, California Geological
> Survey, which may be privileged, confidential and exempt from disclosure
> under applicable law, including the Electronic Communications Privacy
> Act. If the reader of this communication is not the intended recipient,
> you are hereby notified that any dissemination, distribution, or copying
> of this communication is strictly prohibited.

--
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341