/**
* Return the results so far.
* <p>
* @param reverse if true then clockwise (instead of counter-clockwise)
* traversal counts as a positive area.
* @param sign if true then return a signed result for the area if
* the polygon is traversed in the "wrong" direction instead of returning
* the area for the rest of the earth.
* @return PolygonResult(<i>num</i>, <i>perimeter</i>, <i>area</i>) where
* <i>num</i> is the number of vertices, <i>perimeter</i> is the perimeter
* of the polygon or the length of the polyline (meters), and <i>area</i>
* is the area of the polygon (meters<sup>2</sup>) or Double.NaN of
* <i>polyline</i> is true in the constructor.
* <p>
* More points can be added to the polygon after this call.
**********************************************************************/
public PolygonResult Compute(bool reverse, bool sign)
{
if (_num < 2)
{
return(new PolygonResult(_num, 0, _polyline ? Double.NaN : 0));
}
if (_polyline)
{
return(new PolygonResult(_num, _perimetersum.Sum(), Double.NaN));
}
GeodesicData g = _earth.Inverse(_lat1, _lon1, _lat0, _lon0, _mask);
Accumulator tempsum = new Accumulator(_areasum);
tempsum.Add(g.GeodesicScale12);
int crossings = _crossings + Transit(_lon1, _lon0);
if ((crossings & 1) != 0)
{
tempsum.Add((tempsum.Sum() < 0 ? 1 : -1) * _area0 / 2);
}
// area is with the clockwise sense. If !reverse convert to
// counter-clockwise convention.
if (!reverse)
{
tempsum.Negate();
}
// If sign put area in (-area0/2, area0/2], else put area in [0, area0)
if (sign)
{
if (tempsum.Sum() > _area0 / 2)
{
tempsum.Add(-_area0);
}
else if (tempsum.Sum() <= -_area0 / 2)
{
tempsum.Add(+_area0);
}
}
else
{
if (tempsum.Sum() >= _area0)
{
tempsum.Add(-_area0);
}
else if (tempsum.Sum() < 0)
{
tempsum.Add(+_area0);
}
}
return
(new PolygonResult(_num, _perimetersum.Sum(g.Distance), 0 + tempsum.Sum()));
}
/**
* Constructor for PolygonArea.
* <p>
* @param earth the Geodesic object to use for geodesic calculations.
* @param polyline if true that treat the points as defining a polyline
* instead of a polygon.
**********************************************************************/
public PolygonArea(Geodesic earth, bool polyline)
{
_earth = earth;
_area0 = _earth.EllipsoidArea();
_polyline = polyline;
_mask = GeodesicMask.LATITUDE | GeodesicMask.LONGITUDE |
GeodesicMask.DISTANCE |
(_polyline ? GeodesicMask.NONE :
GeodesicMask.AREA | GeodesicMask.LONG_UNROLL);
_perimetersum = new Accumulator(0);
if (!_polyline)
{
_areasum = new Accumulator(0);
}
Clear();
}
public Accumulator(Accumulator a)
{
_s = a._s;
_t = a._t;
}
