def is_ccw(signed_area):
    """Returns True when a ring is oriented counterclockwise

    This is based on the signed area:

     > 0 for counterclockwise
     = 0 for none (degenerate)
     < 0 for clockwise
    """
    if signed_area > 0:
        return True
    elif signed_area < 0:
        return False
    else:
        raise ValueError("Degeneracy: No orientation based on area")