[postgis-devel] [PostGIS] #2002: Circle geometry handling

[PostGIS]

#2002: Circle geometry handling
----------------------+-----------------------------------------------------
 Reporter:  xificurk  |       Owner:  pramsey      
     Type:  defect    |      Status:  new          
 Priority:  medium    |   Milestone:  PostGIS 2.0.2
Component:  postgis   |     Version:  2.0.x        
 Keywords:            |  
----------------------+-----------------------------------------------------
 The documentation states in 4.1.3. SQL-MM Part 3:

 "The exception to this is for a closed circle, where the start and end
 points are the same. In this case the second point MUST be the center of
 the arc, ie the opposite side of the circle."

 But it seems that postgis does not handle these geometries well.

 => SELECT
 ST_AsText(ST_CurveToLine(ST_GeomFromText('CURVEPOLYGON(CIRCULARSTRING(-1
 0,1 0,-1 0))')));
         st_astext
 --------------------------
  POLYGON((1 0,-1 0,-1 0))

 The result is invalid polygon. The workaround is simple - use more points
 in circular string, e.g.:
 => SELECT
 ST_AsText(ST_CurveToLine(ST_GeomFromText('CURVEPOLYGON(CIRCULARSTRING(-1
 0, 0 1, 1 0, 0 -1, -1 0))'), 2));

 st_astext
 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  POLYGON((-1 1.22460635382238e-16,-0.707106781186547
 0.707106781186548,6.12303176911189e-17 1,0.707106781186548
 0.707106781186547,1 0,0.707106781186548
 -0.707106781186547,6.12303176911189e-17 -1,-0.707106781186547
 -0.707106781186548,-1 0))

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2002>
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