Raster based terrain analysis with QGIS

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Raster based terrain analysis with QGIS

Hugentobler  Marco
Hi QGIS devs

I'd like to announce the QGIS raster terrain plugin. It calculates slope, exposition, ruggedness and total curvature based on a 3*3 window for each cell of a raster. The plugin keeps attention that only three raster rows are in virtual memory at a time, so it is also possible to process large rasters.
If you like to test the plugin, you find the source on:
http://karlinapp.ethz.ch/raster_terrain_analysis.tgz
Just unzip it in the src/plugins directory and add 'raster_terrain_analysis' as a new subdirectory in src/plugins/CMakeList:

SUBDIRS (copyright_label
  delimited_text
  interpolation
  north_arrow
  scale_bar
  oracle_raster
  raster_terrain_analysis
  )

Note that the code is not well tested yet, so drop me a mail if a result seems strange or you have other comments / suggestions / code improvements.

I thought that this plugin could ev. go into the upcoming analysis library of QGIS. Btw. are there any objections on merging the branch with the analysis library after the release of 1.2 and using the library for the interpolation and raster terrain plugin? fTools will come later I think as it probably is a lot of work to port the python code to C++...

Regards,
Marco



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Re: Raster based terrain analysis with QGIS

Borys Jurgiel-2
> Btw. are there any objections on merging the branch with the
> analysis library after the release of 1.2 and using the library for the
> interpolation and raster terrain plugin?

Of course +1 ! This is an essential functionality :)
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Re: Raster based terrain analysis with QGIS

Tim Sutton-4
In reply to this post by Hugentobler Marco
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi

Hugentobler Marco wrote:
> Hi QGIS devs
>
> I'd like to announce the QGIS raster terrain plugin. It calculates slope, exposition, ruggedness and total curvature based on a 3*3 window for each cell of a raster. The plugin keeps attention that only three raster rows are in virtual memory at a time, so it is also possible to process large rasters.
> If you like to test the plugin, you find the source on:
> http://karlinapp.ethz.ch/raster_terrain_analysis.tgz

Cool!

> Just unzip it in the src/plugins directory and add 'raster_terrain_analysis' as a new subdirectory in src/plugins/CMakeList:
>
> SUBDIRS (copyright_label
>   delimited_text
>   interpolation
>   north_arrow
>   scale_bar
>   oracle_raster
>   raster_terrain_analysis
>   )
>
> Note that the code is not well tested yet, so drop me a mail if a result seems strange or you have other comments / suggestions / code improvements.
>
> I thought that this plugin could ev. go into the upcoming analysis library of QGIS. Btw. are there any objections on merging the branch with the analysis library after the release of 1.2 and using the library for the interpolation and raster terrain plugin? fTools will come later I think as it probably is a lot of work to port the python code to C++...
>

Yes I think its a great idea to merge it with the analysis branch / make
it part of the analysis lib - I was hoping to work some more on that in
the hackfest too.

Regards


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Re: Raster based terrain analysis with QGIS

pcav
In reply to this post by Hugentobler Marco
Hugentobler Marco ha scritto:

> I thought that this plugin could ev. go into the upcoming analysis library of
> QGIS. Btw. are there any objections on merging the branch with the analysis
> library after the release of 1.2 and using the library for the interpolation
> and raster terrain plugin? fTools will come later I think as it probably is a
> lot of work to port the python code to C++...

+1 Thanks Marco.
Does it work with any raster source?
It will be interesting to compare the results with analogous modules from GRASS.
All the best.
--
Paolo Cavallini: http://www.faunalia.it/pc
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Re: Raster based terrain analysis with QGIS

Carson Farmer
In reply to this post by Tim Sutton-4
Hi all,
>>
>> I thought that this plugin could ev. go into the upcoming analysis library of QGIS. Btw. are there any objections on merging the branch with the analysis library after the release of 1.2 and using the library for the interpolation and raster terrain plugin? fTools will come later I think as it probably is a lot of work to port the python code to C++...
> Yes I think its a great idea to merge it with the analysis branch / make
> it part of the analysis lib - I was hoping to work some more on that in
> the hackfest too.
>  
The hackfest would be a good place to get this going again, and I'm
looking forward to this. Unfortunately my PhD has been getting in the
way of my QGIS stuff over the past few months, so there has been very
little new work done lately. As for merging the raster analysis stuff
with the analysis branch, this sounds fantastic (+1), and will be a very
good step towards making QGIS a well rounded platform for GIS analysis.

Carson

--
Carson J. Q. Farmer
ISSP Doctoral Fellow
National Centre for Geocomputation (NCG),
National University of Ireland, Maynooth,
Email: [hidden email]
Web:   http://www.carsonfarmer.com/
       http://www.ftools.ca/

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AW: Raster based terrain analysis with QGIS

Hugentobler  Marco
In reply to this post by pcav
Hi Paolo

>Does it work with any raster source?

It should work with every GDAL supported source. Currently it always takes the first band as input (assuming that the terrain rasters are usually single band rasters).

>It will be interesting to compare the results with analogous modules from GRASS.

Yes, slope and aspect can be compared with results from GRASS commands (r.slope.aspect). I tested the slope and found that, for my test area, the results are identical (as they also used Horn's algorithm for derivative estimation). One small difference is that r.slope.aspect fills the border cells with null values while the raster terrain plugin tries to estimate these too.

Performance comparison is surely also interesting. Slope calculation on my test raster (1.6 GB large GeoTiff) took 2min5s with the raster plugin (saved to GeoTiff). The same raster, imported into grass with r.in.gdal, took 3min12s to process with r.slope.aspect. But this is not a systematic evaluation at all, just a single test. It surely depends also on the raster format you use for reading/writing in the plugin.

Regards,
Marco


-----Urspr√ľngliche Nachricht-----
Von: Paolo Cavallini [mailto:[hidden email]]
Gesendet: Sa 22.08.2009 08:43
An: Hugentobler  Marco
Cc: [hidden email]
Betreff: Re: [Qgis-developer] Raster based terrain analysis with QGIS
 
Hugentobler Marco ha scritto:

> I thought that this plugin could ev. go into the upcoming analysis library of
> QGIS. Btw. are there any objections on merging the branch with the analysis
> library after the release of 1.2 and using the library for the interpolation
> and raster terrain plugin? fTools will come later I think as it probably is a
> lot of work to port the python code to C++...

+1 Thanks Marco.
Does it work with any raster source?
It will be interesting to compare the results with analogous modules from GRASS.
All the best.
--
Paolo Cavallini: http://www.faunalia.it/pc

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plugins with duplicate names in plugin installer

Maxim Dubinin
In reply to this post by Borys Jurgiel-2
Hi all and Borys,

just a note, seems like plugins with the same name from different repos are
not duplicated as I guess they should. This is not the time to ring
the bells, but wait till we have hundreds.

For example TestPlugin by Vulcan is overriding my very own with the same name.

Maxim

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