Circle geometry handling

[xificurk]

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))

[pramsey]

This is now fixed in 2.0 and trunk, not sure at what revision.

SELECT ST_Area(ST_CurveToLine(ST_GeomFromText('CURVEPOLYGON(CIRCULARSTRING(-1 0,1 0,-1 0))')));