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On 10/01/2012 04:32 PM, M.E.Dodd wrote:
<blockquote
cite="mid:9932A16F9CE9264FAC3F2E0E008E122107A12385D0@KIELDERCMS1.open.ac.uk"
type="cite">
<pre wrap="">Is it possible to define an area to do the surface generation within? I see there are options to define this with a simple box or drag on screen but if you want to say use a country outline map as the boundary and do the interpolation within this?
</pre>
</blockquote>
<br>
What I would do is use the gdalwarp -cutline option to clip the
surface raster to the country polygon before creating the contours.<br>
In QGIS it's Raster->Extraction->Clipper, then choose the
"mask" parameter.<br>
<br>
<blockquote
cite="mid:9932A16F9CE9264FAC3F2E0E008E122107A12385D0@KIELDERCMS1.open.ac.uk"
type="cite">
<pre wrap="">
-----Original Message-----
From: Micha Silver [<a class="moz-txt-link-freetext" href="mailto:micha@arava.co.il">mailto:micha@arava.co.il</a>]
Sent: 01 October 2012 14:16
To: AJAY KUMAR MULAKALA
Cc: <a class="moz-txt-link-abbreviated" href="mailto:qgis-user@lists.osgeo.org">qgis-user@lists.osgeo.org</a>
Subject: Re: [Qgis-user] How to generate (vector)contour lines for point data?
On 10/01/2012 06:50 AM, AJAY KUMAR MULAKALA wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Dear sir,
Suggest me how to generate contour lines for a point data (particular
to generate contour lines about an attribute information of point
data)
</pre>
</blockquote>
<pre wrap="">
You will need two steps. First use the points to create a raster surface. In the Raster menu, choose Analysis->Grid. With this GDAL tool you can create a raster using some simple algorithms. THen using this new raster as your surface, use the GDAL tool
Raster->Extraction->Contour to get vector contour lines.
(Note that if you switch to the GRASS plugin, there are more interpolation algorithms available, especially "regularized spline"=rst, for creating the surface raster)
Regards,
Micha
</pre>
<blockquote type="cite">
<pre wrap="">Regards,
AJAY KUMAR
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</pre>
</blockquote>
<pre wrap="">
--
Micha Silver
GIS Consultant, Arava Development Co.
<a class="moz-txt-link-freetext" href="http://www.surfaces.co.il">http://www.surfaces.co.il</a>
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</pre>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Micha Silver
GIS Consultant, Arava Development Co.
<a class="moz-txt-link-freetext" href="http://www.surfaces.co.il">http://www.surfaces.co.il</a></pre>
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