Hi Stefan. You guessed right, it's buildings generalization. I know jts and geos quite well but unfortunatly I can't use them because I'm working directly on oracle with plsql. I think buffer is the way, but not the one oracle provides because it rounds the corners...
Bye, Giovanni 2010/5/7 Stefan Steiniger <sst...@geo.uzh.ch>: > how about using R it has alpha shapes and a-like? > > What you describe sounds like a problem in map generalization. I.e. the > approach of buffering is something what a colleague of mine once implemented > to generalize house-blocks for maps (aggregate the single buildings). > Unfortunately I don't know of any accessible code for that. > > If you are proficient in Java or C++ you could make you custom > implementation with JTS or Geos (sounds easy to me). > > on what geographic objects are you working on? and how much does the shape > to be need to maintained? > > stefan > > G. Allegri wrote: >> >> <Aside> >> A nice implementation of alpha shapes with jts: >> http://www.mail-archive.com/jts-de...@lists.jump-project.org/msg01019.html >> </Aside> >> >> 2010/5/6 G. Allegri <gioha...@gmail.com>: >>> >>> Thanks Andrea for the links. Yes, I think the problem is similar, in >>> fact I was also looking for concave hull and alpha shapes algoithms, >>> but the only open solution I've found is from CGAL [1] and... it's too >>> complex to extract and reimplement in my context (database procedural >>> programming). >>> >>> IWe have implemented something very "rude": >>> >>> 1 - logically aggregate polyongs in clusters (given a certain distance) >>> 2 - buffer each polygon mantaining the shape (not the usual buffer, >>> which make rounded artifacts) >>> 3 - geometrical union >>> 4 - shrink the result (unbuffer) >>> >>> But I have the time for a long holiday waiting the end of the process :) >>> >>> [1] >>> http://www.cgal.org/Manual/last/doc_html/cgal_manual/Alpha_shapes_2/Chapter_main.html >>> >>> 2010/5/6 Andrea Aime <aa...@opengeo.org>: >>>> >>>> G. Allegri ha scritto: >>>>> >>>>> I'm looking for an algorithm to do polygon cluster aggregation, >>>>> similar to the ArcInfo "Aggregate Polygon" [1]. >>>>> I know about GEOS "Cascaded Union", but I need two more features: >>>>> >>>>> 1 - clustering of polygons that fall within a a certain threshold >>>>> distance from each other >>>>> 2 - mantain orthogonality, i.e. the original angles/shapes >>>> >>>> I don't know of any such implementation, but it looks somewhat >>>> similar to the computation of a concave hull: >>>> >>>> http://ubicomp.algoritmi.uminho.pt/local/concavehull.html >>>> >>>> http://stackoverflow.com/questions/83593/is-there-an-efficient-algorithm-to-generate-a-2d-concave-hull >>>> >>>> Cheers >>>> Andrea >>>> >>>> -- >>>> Andrea Aime >>>> OpenGeo - http://opengeo.org >>>> Expert service straight from the developers. >>>> _______________________________________________ >>>> Discuss mailing list >>>> Discuss@lists.osgeo.org >>>> http://lists.osgeo.org/mailman/listinfo/discuss >>>> >> _______________________________________________ >> Discuss mailing list >> Discuss@lists.osgeo.org >> http://lists.osgeo.org/mailman/listinfo/discuss >> >> > _______________________________________________ > Discuss mailing list > Discuss@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/discuss > _______________________________________________ Discuss mailing list Discuss@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/discuss