[postgis-users] Is CIRCULARLINESTRING ready for use?
rindahl at lrcwe.com
Thu Jul 3 10:07:48 PDT 2008
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?
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.
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.
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