[GRASS-dev] Introduction and GSoC

Moritz Lennert mlennert at club.worldonline.be
Tue Apr 3 10:57:39 EDT 2012

On 03/04/12 16:12, Eric Momsen wrote:
> Thanks for the input!  I added some more questions below.
> Also, later today I will probably post to R-Sig-Geo (or some other
> list?) to ask what tools people currently use, and what areas they
> would find most helpful to be integrated into GRASS.  That might help
> focus where I should spend the time.
> On Mon, Apr 2, 2012 at 6:42 AM, Moritz Lennert
> <mlennert at club.worldonline.be>  wrote:
>> On 30/03/12 23:56, Eric Momsen wrote:
>>> I am reading more about image classification (from
>>> http://grass.osgeo.org/wiki/GRASS_SoC_Ideas ):
>>> 4. Implement image segmentation algorithms and tools
>>> 5. Implement region-based classification
>>> 6. Implement hierarchical classification tools (e.g. being able to
>>> create a large class "forest", with subclasses of different types of
>>> forests)
> ...
>> Concerning the ideas:
>> 4. Currently GRASS does not provide any image segmentation as such. i.smap
>> contains image segmentation in its process, but the user cannot get
>> segmented outputs. Many algorithms exist and its an ongoing field of
>> research. FLOSS software that provide such algorithms include Orfeo Toolbox
>> (OTB), SAGA, R, Sextante (?) and probably a whole series of others. I think
>> the implementation of a series of such algorithms could be a project on its
>> own.
> Does it make more sense to implement the algorithms again, or pick the
> most useful that are implemented in some other FLOSS and provide an
> easy integration to access them from the GRASS front end?  (I'm
> thinking of v.krige which uses existing R packages to do the
> processing work.)
> Has Sextante or OTB been tied into GRASS in this manner?

I personally am a bit weary of increasing dependencies between packages, 
but at the same time, why re-invent the wheel. Integrating the OTB 
algorithms into GRASS would definitely be a great plus.

This said, several FOSS4G programs out there already play the role of 
integrators (e.g. QGIS, gvSIG) and I'm not sure that GRASS should try to 
go the same direction. Generally, I'd say: let GRASS do really well what 
it does, and not try to integrate everything.

So, the discussion boils down to: what do we think should be integral 
part of GRASS (the same question is true for the proposal concerning a 
PostGIS manager).

>> 5. One of the main applications of image segmentation today is in
>> region-based classification of very high resolution imagery. As with current
>> resolutions individual objects are composed of many pixels, it is often more
>> efficient to first identify "objects" or homogeneous multi-pixel regions in
>> the image through segmentation and then to classify these regions. OTB
>> provides this I think, but I don't know if any other FLOSS software does. 5
>> depends on 4, so it is only possible if 4. is limited to the strict minimum
>> in terms of segmentation algorithms and then focus is put on 5. Maybe a bit
>> too ambitious.
> If I can use the OTB implementation from GRASS, then I will include
> this as a stretch goal if time remains at the end of the summer.

As always, we should check how much integrating OTB means in terms of 
added dependencies for GRASS. Also, OTB is C++ which AFAICT tell often 
spells trouble. Then again, there is a Python wrapper which you could use.

Don't know what others think of all this.


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