GMSGeometrySignedArea
extern double GMSGeometrySignedArea(GMSPath *_Nonnull path)Returns the signed area of a geodesic polygon defined by path on Earth.
The result has the same absolute value as GMSGeometryArea(); it is positive if the points of
path are in counter-clockwise order, and negative otherwise.
The same restrictions as on GMSGeometryArea() apply.