[Qgis-user] QGIS - help: filled contour lines from raster layer data

[KOHLMANN Hannes]

Hello Nicolas,

thank you for your answer! Reinstalling Osgeo removed the error I mentioned. Now I was able to get contour lines (!! When I chose „Auto“ for the advanced preference v.out.ogr) with r.contour.step, where I chose the minimum 0 and maximum 10 with step size 1. After getting the contour vector layer, I transformed it with the tool Vector --> Geometry tools --> from line to polygon which gives me areas, that I gave 5 different colors then.
Snapshots of the density raster file and the result (filled contours) are here:
Density: https://postimg.org/image/86yowo0oj/
Filled Contours: https://postimg.org/image/ugk8s349n/

I’m not really satisfied with that result because:

1)      Why is it, that there are white areas where actually there should be other than blank? Is it because the contour lines are not closed for these areas? I strongly think so - what would be recommended to avoid that ?

2)      When I select „area“ under the advanced preferences in r.contour.step, I get NOTHING … not a single value or color… do I have to configure the parameters of r.contour.step/level differently?

If you are interested in trying to reproduce that, here is the corresponding density .dat raster file. I gave it the style of 5 different colors, equidistantly distributed.
https://www.dropbox.com/s/bpkfkvos6ss3wx5/density_2015.dat?dl=0

Thank you very much for your help, it took me already one step closer tot he truth :D

Best regards,
Hannes

Von: Qgis-user [mailto:qgis-user-bounces at lists.osgeo.org] Im Auftrag von Nicolas Cadieux
Gesendet: Donnerstag, 8. September 2016 19:57
An: qgis-user at lists.osgeo.org<mailto:qgis-user at lists.osgeo.org>
Betreff: Re: [Qgis-user] QGIS - help: filled contour lines from raster layer data

Hi,

I am not sure why you get that error but the r.contour.level will give you what you need if you select "area" in the v.out.org<http://v.out.org> parameter.  That will give you polygons that you can color the fill area. If you have installed the latest version of Qgis, your processing toolbox could be a mix of old and new tools.  If this is the case, I would do complete reinstall deleting all the old plugins.

Nicolas

Envoyé de mon iPad

Le 8 sept. 2016 à 08:47, KOHLMANN Hannes [via OSGeo.org<http://osgeo.org>] <[hidden email]</user/SendEmail.jtp?type=node&node=5284798&i=0>> a écrit :
Hello dear QGis users!

A collegue and me were wondering if it is possible to create contour lines, or more important for us, FILLED contour lines (areas) for RASTER LAYER data!
We are both very positive that this once worked and we have done that. Now we cannot find the way to reproduce that anymore.
On the one hand, we thought that we had done it with the gdal-Contour tool in QGIS (Raster->Extract->Contour), but now we can’t find an option to generate filled contour areas, like
it is possible with the installable extension „Contour Plugin“ (which is only possible to use with a point vector layer, but this is exactly what we think that we have done to a raster layer file!).

1.      Now the question: was that ever possible to do with the gdal-contour plugin? Or not…


2.      On the other hand, we also tried to use the GRASS Gis algorithms r.contour.level or r.contour.step, etc in the processing toolbox, but they keep giving us the error message: „environment can only contain strings See log for more details“. What ist he problem here? Does it have to do with the new version Grass Gis 7?


3.      Bottom line is: We have got a .dat file, which is a raster layer with valued pixels that we are displaying in spectral colors. Now we want to extract the contour lines and to have a color fill between those contour lines. How would you do this – is there an easy solution, which differs from the numerous tutorials on the web, which seem to be a lot more complicated than what we actually remember to have done?


Thank you very much in advance, any answer would be very helpful!

Best regards,
Hannes Kohlmann

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