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
<[email protected]> 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.
Moritz
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