[Qgis-user] How to generate (vector)contour lines for point data?

[M.E.Dodd]

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?

-----Original Message-----
From: Micha Silver [mailto:micha at arava.co.il] 
Sent: 01 October 2012 14:16
To: AJAY KUMAR MULAKALA
Cc: qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] How to generate (vector)contour lines for point data?

On 10/01/2012 06:50 AM, AJAY KUMAR MULAKALA wrote:
> 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)
>

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

> Regards,
> AJAY KUMAR
>
>
>
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--
Micha Silver
GIS Consultant, Arava Development Co.
http://www.surfaces.co.il

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