[Qgis-developer] Handling of fuzzy boundaries

[Tim Sutton]

Hi

On Wed, 2010-09-22 at 17:47 +0200, Annina Hirschi Wyss wrote:
> Hello,
> 
> I'm preparing my master's thesis on the subject of handling fuzzy objects using the fuzzy logic, with the focus on geometries (not on the thematic level).
> I wanted to know, if there has already been a discussion about implementing this in QGIS or in a plugin.
> 

As far as I know, no one is working on this or has discussed it. But its
an interesting topic and it would be nice to see some real innocation
happening in QGIS.

> Showing the uncertainty of boundaries is needed in some cases of spatial planning, when the "crisp" geometries are not yet defined.
> 
> A possible use case could also be to draw a polygon with certain attributes, then the border of the polygon "copied" to one or more oriented polyline layers with special attributes (e. g. the distance of the uncertainty, to which the fuzzy-function is applied). These polylines are linked by a foreign key to the polygon-feature. This would certainly require the use of a database, namely Postgre/PostGIS.
> A polyline layer (linked to the polygon) can also be "crisp" e.g. if the border is a street or a river. So it should be possible to combine crisp and fuzzy segments for the same polygon.
> Visualising this could result in a polygon with a sort of "thick pen-trace"  (the thickness corresponding to the distance-attribute of the polyline) boundary, showing the uncertain band. The thickness corresponds to the distance-attribute of the polyline.
> 
> Another possible visualisation (sort of fuzzy buffers) is presented in the following paper: http://www.geo3.nl/12%20fuzzy%20set%20theory.pdf (fig. 1b).
> 

Right - one could probably apply blur effects and similar to lines to
represent their fuzzyness - Qt4 already has some infrastructure for this
kind of thing e.g.
http://doc.qt.nokia.com/4.6/qgraphicsdropshadoweffect.html#details 

I'm not sure about using two separate layers as you describe above - it
might be nicer to make fuzziness simply an attribute of the feature -
though I guess it doesnt cope well for the scenario where individual
segments of a feature have different fuzziness levels...


> If there are developers interested in this, I would be glad to know, as my own programming skills are rather basic.


Look forward to seeing your proof of concepts!

Regards

Tim

> 
> Thanks in advance
> Annina_______________________________________________
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