[postgis-tickets] [PostGIS] #2181: ST_Buffer returning multipolygon with linestring/polygon input (was: ST_Buffer returning multipolygon with linestring input)

[PostGIS]

#2181: ST_Buffer returning multipolygon with linestring/polygon input
----------------------------------------------+-----------------------------
 Reporter:  mcastrog                          |       Owner:  pramsey     
     Type:  defect                            |      Status:  new         
 Priority:  medium                            |   Milestone:  PostGIS GEOS
Component:  postgis                           |     Version:  2.0.x       
 Keywords:  Buffer, linestring, multipolygon  |  
----------------------------------------------+-----------------------------
Changes (by rnuske):

 * cc: rnuske (added)
  * version:  1.5.X => 2.0.x


Comment:

 Reproduced bug with relatively simple polygon.

 One of many polygons received from a colleague produces a multipolygon if
 buffered with buffer radii between 40.5 and 42.3. Other buffer radii or a
 different "start point" in the order of the vertices lead to the expected
 regular polygons without additional slivers or splinters


 Query using simplified version of problematic polygon
 {{{
 SELECT ST_AsText(ST_Buffer(ST_GeomFromText('POLYGON((19.4994 56.0304,
 19.2074 56.0271, 18.9318 56.0205, 18.8957 57.9268, 20.5001 57.9498,
 20.0079 56.0369, 19.7389 56.0304, 19.4994 56.0304))'), 42.0));
 }}}

 results in
 {{{
 "MULTIPOLYGON(((19.7367211896429 14.0304,19.7705233164382
 14.0307820103371,19.7389 14.0304,19.7367211896429
 14.0304)),((19.9343358615234 14.0327608693757,11.7006495228381
 14.6476772442749,3.74363996706844 16.8628724567734,-3.62598135388737
 20.5924531953819,-10.1232010579226 25.6921813271142,-15.4967450996707
 31.9648295183871,-19.5387965650002 39.1678088222387,-22.093032800601
 47.0225505845648,-23.0606710500053 55.2252798327099,-23.0967710500053
 57.1315798327099,-22.4407679720923 65.3629559687913,-20.1869395043865
 73.3068939324235,-16.4224054354575 80.6563276776687,-11.2926805712663
 87.127171204565,-4.99604998629464 92.4692996575579,2.22409551437942
 96.4762176852911,10.0886674559795 98.9930413396766,18.2936676174523
 99.9224849808449,19.8980676174523 99.9454849808449,28.4228349595372
 99.1957727823327,36.6186842709601 96.7337044076271,44.1453589826341
 92.6614943931604,50.6903837894731 87.1482034616806,55.9820372870512
 80.4227198449549,59.8006326808134 72.7642568244779,61.9876382410949
 64.4907609916044,62.4522588617096 55.9457124665125,61.175205483978
 47.4838650743824,60.683005483978 45.5709650743824,58.0642841438528
 38.2686241721232,54.1472040167705 31.5724784607419,49.0654030065054
 25.7109784307067,42.9922554664985 20.8840992041937,36.1349572365661
 17.2565180409666,28.7274568016185 14.9519960913458,21.022473738028
 14.0491560723953,20.753473738028 14.0426560723953,19.9343358615234
 14.0327608693757)),((19.9358193041834 14.0326500814315,19.9475017979551
 14.0327821096145,19.9373172271422 14.0325382120551,19.9358193041834
 14.0326500814315)))"
 }}}



 {{{
 SELECT postgis_full_version();
 "POSTGIS="2.0.3 r11128" GEOS="3.3.8-CAPI-1.7.8" PROJ="Rel. 4.8.0, 6 March
 2012" GDAL="GDAL 1.10.0, released 2013/04/24" LIBXML="2.8.0"
 LIBJSON="UNKNOWN" RASTER"
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2181#comment:4>
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