This function joins a series of points specified in the physical
coordinate system of a PlotPlot by drawing a sequence of geodesic
curves. It is equivalent to making repeated use of the astCurveastCurve
function (q.v.), except that astPolyCurve will generally be more
efficient when drawing many geodesic curves end-to-end. A
typical application of this might be in drawing contour lines.
As with astCurve, full account is taken of the MappingMapping between
physical and graphical coordinate systems. This includes any
discontinuities and clipping established using astClipastClip.