STLineToCurve. A Function that Converts a LineString to a CircularString, CompoundCurve or CurvePolygon.
The STLineToCurve function analyses a LineString looking for CircularString elements among its vertices (often LineStrings are created from curve elements by “stroking” especially where the processing software does not support CircularStrings). Any constructed CircularStrings are combined with other LineStrings to create CompoundCurves or CurvePolygons.