The recent JTS has a nice buffering options, namely the mitre buffer. It does not have rounded corners, and has been very useful to me (i.e., we can physically survey-out the buffer on the ground with fewer points to locate and stake out). http://lin-ear-th-inking.blogspot.com/2007/12/new-buffer-styles-in-jts-19.html
Although I'm no expert at plsql, it appears it can be extended with java, so maybe it could be possible to wrap the Oracle WKT/B(?) through JTS: http://www.devshed.com/c/a/Oracle/Extending-PLSQL-with-Java-Libraries/ Someone must have done this for plsql in the past ... -Mike On 9 May 2010 06:01, G. Allegri <gioha...@gmail.com> wrote: > 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 > _______________________________________________ Discuss mailing list Discuss@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/discuss