[Gvsig_english] QUESTION gvSIG 1.9 (BN 1253) -- Corrupted Polygon / Create new polygon using nodes

[Jorge Gaspar Sanz Salinas]

El 01/07/10 12:08, Antonio Falciano escribió:
> Il 01/07/2010 10.56, Simon Cropper (Botanicus Australia Pty Ltd) ha scritto:
>> Hi,
>>
>> I have inherited a polygon -- nodes in the polygon do not run
>> sequentially from clockwise or anti-clockwise. This is throwing an error.
>>
>> I was able to extract the nodes from the polygon but have had problems
>> finding the routine to create a new polygon using these points (there is
>> no holes in the polygon).
>>
>> Can anyone please point me to a suitable routine?
> 
> Hi Simon,
> you can try with the SEXTANTE library: in detail, applying "Minimum
> enclosing shapes" (Convex hull) on vertices and then subtract the more
> external triangles (selected manually) computed with "Delauney
> triangulation". This is a quite huge task, also known as "Concave hull".
> I don't know if this problem has been solved in GFOSS world...
> http://code.flickr.com/blog/2008/10/30/the-shape-of-alpha/
> Cheers,
> Antonio
> 

Schuyler Erle developed for flickr a free software to create alpha
shapes[1], but the trac/svn[2] is closed now...

More info about the flickr project at [3]

It would be great to have a SEXTANTE geoprocess for that, indeed.

Best

[1] http://biogeometry.duke.edu/software/alphashapes/index.html
[2] http://code.flickr.com/trac/browser/trunk/clustr
[3] http://code.flickr.com/blog/2008/10/30/the-shape-of-alpha/


-- 
Jorge Gaspar Sanz Salinas
gvSIG Team at Prodevelop
Technical Collaborations Manager
http://www.gvsig.org
http://www.gvsig.com