/**
* Set the central point of the projection
*
* @param[in] lat0 latitude of center point of projection (degrees).
* @param[in] lon0 longitude of center point of projection (degrees).
*
* \e lat0 should be in the range [−90°, 90°].
**********************************************************************/
public void Reset(double lat0, double lon0)
{
_meridian = _earth.Line(lat0, lon0, 0,
GeodesicMask.LATITUDE | GeodesicMask.LONGITUDE |
GeodesicMask.DISTANCE | GeodesicMask.DISTANCE_IN |
GeodesicMask.AZIMUTH);
double f = _earth.Flattening();
GeoMath.Sincosd(LatitudeOrigin(), out _sbet0, out _cbet0);
_sbet0 *= (1 - f);
GeoMath.Norm(ref _sbet0, ref _cbet0);
}
/**
* Forward projection, from geographic to Cassini-Soldner.
*
* @param[in] lat latitude of point (degrees).
* @param[in] lon longitude of point (degrees).
* @param[out] x easting of point (meters).
* @param[out] y northing of point (meters).
* @param[out] azi azimuth of easting direction at point (degrees).
* @param[out] rk reciprocal of azimuthal northing scale at point.
*
* \e lat should be in the range [−90°, 90°]. A call to
* Forward followed by a call to Reverse will return the original (\e lat,
* \e lon) (to within roundoff). The routine does nothing if the origin
* has not been set.
**********************************************************************/
public void Forward(double lat, double lon,
out double x, out double y, out double azi, out double rk)
{
if (!Init())
{
x = double.NaN;
y = double.NaN;
azi = double.NaN;
rk = double.NaN;
}
double e;
double dlon = GeoMath.AngDiff(LongitudeOrigin(), lon, out e);
double sig12, s12, azi1, azi2;
sig12 = _earth.Inverse(lat, -Math.Abs(dlon), lat, Math.Abs(dlon), out s12, out azi1, out azi2);
sig12 *= 0.5;
s12 *= 0.5;
if (s12 == 0)
{
double da = GeoMath.AngDiff(azi1, azi2, out e) / 2;
if (Math.Abs(dlon) <= 90)
{
azi1 = 90 - da;
azi2 = 90 + da;
}
else
{
azi1 = -90 - da;
azi2 = -90 + da;
}
}
if (dlon < 0)
{
azi2 = azi1;
s12 = -s12;
sig12 = -sig12;
}
x = s12;
azi = GeoMath.AngNormalize(azi2);
GeodesicLine perp = _earth.Line(lat, dlon, azi, GeodesicMask.GEODESICSCALE);
double t;
perp.GenPosition(true, -sig12,
GeodesicMask.GEODESICSCALE,
out t, out t, out t, out t, out t, out t, out rk, out t);
double salp0, calp0;
GeoMath.Sincosd(perp.EquatorialAzimuth(), out salp0, out calp0);
double
sbet1 = lat >= 0 ? calp0 : -calp0,
cbet1 = Math.Abs(dlon) <= 90 ? Math.Abs(salp0) : -Math.Abs(salp0),
sbet01 = sbet1 * _cbet0 - cbet1 * _sbet0,
cbet01 = cbet1 * _cbet0 + sbet1 * _sbet0,
sig01 = Math.Atan2(sbet01, cbet01) / GeoMath.Degree;
_meridian.GenPosition(true, sig01,
GeodesicMask.DISTANCE,
out t, out t, out t, out y, out t, out t, out t, out t);
}
