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I'm using QGIS 2.4.0 and I have a shapefile of points with elevation data and X and Y coordinates. I'm using windows 7 OS.

The idea is to create a contour line SHP using my point data.

My question is: How do I start working on that issue? Is there a function? Is there a step by step process?

PolyGeo
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Edixon Gutierrez
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  • I was searching around and it looks like in ArcGIS the create a TIN function creates a TIN file from points with elevation data, is there a way to make it the same in QGIS? – Edixon Gutierrez Sep 05 '14 at 19:46
  • http://docs.qgis.org/testing/en/docs/user_manual/plugins/plugins_interpolation.html – radouxju Sep 05 '14 at 19:50
  • Thanks for your answer radauxju. This is what I got following the steps:

    1- Create TIN using interpolation.

    2- Create contourlines from TIN.

    http://prntscr.com/4k08tc

    Not sure if this is the answer but is what I had in mind. Also not sure if I should marked it as an answer because @WhiteboxDev answer is a good one, the only issue is that is not working.

     – Edixon Gutierrez Sep 05 '14 at 20:24

3 Answers3

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Using the Contour plugin. Generate isolines and/or filled contours a set of data points.

egofer
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There are a number of tools in QGIS for generating contours, though most require a raster input rather than vector points. As such, your best bet is to use the Contour Lines From Points tool:

Models -> [Example Models] -> Contour lines from points

You have to set up the SAGA plugin. You can do it based on the documentation: QGIS Configuring external applications.

The tool takes a vector input and generates a contour line vector. You simply need to enter your points file and the attribute containing the 'z-value', an output grid resolution, and a contour interval.

WhiteboxDev
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  • Thanks @WhiteboxDev, I was trying to install the plugin but I got this error, is in Spanish http://prntscr.com/4k0377, in the dialog box says that the plugin is broken ( more or less: El complemento está roto). – Edixon Gutierrez Sep 05 '14 at 20:12
  • @EdixonGutierrez Wish I could help you but I'm on Mac OSX, and the install for QGIS and all it's various plugins is quite different I suspect. You might consider posting another question regarding your plugin install issues. – WhiteboxDev Sep 05 '14 at 20:55
  • Is OK @WhiteboxDev, if there's somebody that can help I may ask for some help in a post here. I'm really bad with plugins bugs and so. Thanks for your answer both are correct answer, I hope I can check them both. – Edixon Gutierrez Sep 05 '14 at 21:00
  • @EdixonGutierrez, Gabor Farkas edited my answer to include a link to 'QGIS Configuring external applications', which may be able to help with your install issues. Best of luck. – WhiteboxDev Sep 05 '14 at 21:02
  • I'll give it a try. I'll post the solution to that issue if I find it. – Edixon Gutierrez Sep 05 '14 at 21:05
  • This blog is about using GDAL contour tool http://woostuff.wordpress.com/2011/09/27/generating-contours-using-gdal-via-shell-or-qgis/. Gdal_contour is a raster tool so before using it an extra step of convertion point data into raster is needed. Gdal_grid is one possible tool for that http://www.gdal.org/gdal_grid.html. – user30184 Sep 05 '14 at 21:30
  • @WhiteboxFev, I ran the model and the result was a very nice contours layer but with only positive values (>=0), while my data contains also negattive values. Are you familiar with this bug? – H.Wiener Nov 19 '14 at 11:46
  • @EdixonGutierrez You don't need to install the "Contour lines from points" as it comes as part of QGIS 2.4 So maybe the problem is somewhere else in your QGIS installation? There's also a plugin for contours: https://plugins.qgis.org/plugins/contour/ – H.Wiener Nov 19 '14 at 11:52
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Maybe it is too late to answer, but someone like me might have the same need.

I had a layer of points and I only wanted to visualize the perimeter or the contour. In QGIS 2.12 I only had to use the vector Research Tools "Polygon from Layer Extent" (from the vector menu) and voilà! The other option is to use a convex hull.In my case the first option (fastest) solve my problem as my points where regularly arranged in their extent.

FabianUx
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