[postgis-users] Is CIRCULARLINESTRING ready for use?

[Bruce Rindahl]

Mark Leslie wrote:
> Support for CIRCULARSTRING is there.  Loading and retrieving of the 
> supported curved geometries should scale to large numbers perfectly 
> well, but not all the SQL-MM geometries are currently supported.  In 
> particular, PostGIS was choking when I attempted to implement curved 
> polygons.  Index support is complete, but I don't recall any heavy 
> testing to ensure it's solid.  It does manage to calculate a fairly 
> tight bounding box based on the curvature of the segment, not just the 
> defining points, so I would consider it ready for substantial 
> testing.  If only we had a volunteer with a large number of circular 
> string geometries ;)
How about the states of Delaware and Pennsylvania?

  http://en.wikipedia.org/wiki/Twelve-Mile_Circle 

I also have numerous parcels with circular arcs for testing but you must 
tell me what the syntax is.  The documentation gives CIRCULARSTRING(0 0, 
1 1, 1 0) but does not tell you what the points 0 0 , 1 1  and 1 0 
mean.  Three point arc?  Start, end, center?  Let me know and I will 
send you lots of shapes.

See:
http://postgis.refractions.net/pipermail/postgis-devel/2007-September/002778.html

I don't think this post was ever answered.

Finally I have to question the support of circularstrings if we don't 
support ellipses.  The circle of Delaware is an ellipse in every 
projection except geodetic (?).  We can't correctly project a 
circularstring to anything and maintain the spatial relationship.  For 
example in SVG there is no circle command in paths - only ellipses.  A 
circular arc is defined as an ellipse with both radii the same.

Comments??

Bruce