[postgis-tickets] [PostGIS] #2181: ST_Buffer returning multipolygon with linestring input

[PostGIS]

#2181: ST_Buffer returning multipolygon with linestring input
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 Reporter:  mcastrog                          |       Owner:  pramsey
     Type:  defect                            |      Status:  new    
 Priority:  medium                            |   Milestone:         
Component:  postgis                           |     Version:  1.5.X  
 Keywords:  Buffer, linestring, multipolygon  |  
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Comment(by robe):

 Paul or Sandro can chime in on this, but I suspect this is not a bug and
 just that your linestrings are so short.  Even a buffered linestring is
 not guaranteed to return a polygon if it is not simple or is really short
 because at that point the areas start intersecting with each other
 creating pockets which could conceivably turn into small polygons if two
 pockets are close enough.

 The example linestring you have has length of ~99.18 which is smaller than
 your buffer.

 {{{
 SELECT ST_length('LINESTRING(640770.332537465
 216785.425146015,640770.356311913 216785.560172686,640770.475488952
 216786.226162019,640770.647396495 216787.800152365,640770.658978918
 216789.268376902,640770.447752096 216792.399898366,640769.98018796
 216795.624688816,640769.110287021 216798.527305023,640767.648768098
 216801.891389348,640766.02448565 216804.805892778,640764.74005588
 216807.134569434,640763.337363474 216809.560477487,640761.650901703
 216812.246990061,640759.955600712 216815.327305019,640758.482499366
 216817.868732504,640757.383693167 216819.548488661,640756.238862077
 216821.226720821,640754.01503683 216824.434442434,640751.366929134
 216828.435255234,640749.204368809 216832.450088865,640747.25516891
 216836.227787618,640746.014020829 216838.801219168,640745.393751588
 216840.360274284,640744.315976633 216842.854457673,640743.400050801
 216844.65704848,640742.582575565 216846.277673322,640741.52491745
 216848.478638524,640740.503835408 216850.705816576,640739.787553975
 216852.270967708,640739.053289307 216853.851968469,640738.173025147
 216855.546355058,640737.55488951 216856.568961104,640736.817272035
 216857.822910812,640735.910795021 216859.35697228,640734.77510795
 216861.236982439,640733.832969266 216862.938074642,640732.814325629
 216865.039674844,640731.225095251 216869.012141189,640729.979984761
 216871.879095724,640729.445974092 216873.02148841,640729.002794006
 216873.679857725,640728.952197105 216873.745389857,640728.676962154
 216874.089814544)'::geometry)
 }}}

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2181#comment:2>
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