internal static PolarGeoCoordinate Convert(PolarGeoCoordinate source, CoordinateSystems destination)
{
PolarGeoCoordinate retVal;
if (source.CoordinateSystem == CoordinateSystems.OSGB36 && destination == CoordinateSystems.WGS84)
{
retVal = Convert(
source,
EllipseParameter.GetEllipseParameters(EllipseParameter.Ellipses.Airy1830),
HelmertTransform.GetTransform(HelmertTransform.HelmertTransformType.OSGB36toWGS84),
EllipseParameter.GetEllipseParameters(EllipseParameter.Ellipses.WGS84)
);
}
else if (source.CoordinateSystem == CoordinateSystems.WGS84 && destination == CoordinateSystems.OSGB36)
{
retVal = Convert(
source,
EllipseParameter.GetEllipseParameters(EllipseParameter.Ellipses.WGS84),
HelmertTransform.GetTransform(HelmertTransform.HelmertTransformType.WGS84toOSGB36),
EllipseParameter.GetEllipseParameters(EllipseParameter.Ellipses.Airy1830)
);
}
else
{
throw new NotImplementedException("Requested source and destination are not currently supported");
}
retVal.AlignSigFigs(source);
return(retVal);
}
private static PolarGeoCoordinate Convert(
PolarGeoCoordinate originalCoord, EllipseParameter e1, HelmertTransform t, EllipseParameter e2)
{
// -- convert polar to cartesian coordinates (using ellipse 1)
PolarGeoCoordinate p1 = PolarGeoCoordinate.ChangeUnits(originalCoord, AngleUnit.Radians);
double sinPhi = Math.Sin(p1.Lat);
double cosPhi = Math.Cos(p1.Lat);
double sinLambda = Math.Sin(p1.Lon);
double cosLambda = Math.Cos(p1.Lon);
double H = p1.Height;
double eSq = (Math.Pow(e1.SemimajorAxis, 2) - Math.Pow(e1.SemiMinorAxis, 2)) / Math.Pow(e1.SemimajorAxis, 2);
double nu = e1.SemimajorAxis / Math.Sqrt(1 - eSq * sinPhi * sinPhi);
double x1 = (nu + H) * cosPhi * cosLambda;
double y1 = (nu + H) * cosPhi * sinLambda;
double z1 = ((1 - eSq) * nu + H) * sinPhi;
// -- apply helmert transform using appropriate params
double tx = t.tx, ty = t.ty, tz = t.tz;
double rx = t.rx / 3600 * Math.PI / 180; // normalise seconds to radians
double ry = t.ry / 3600 * Math.PI / 180;
double rz = t.rz / 3600 * Math.PI / 180;
double s1 = t.s / 1e6 + 1; // normalise ppm to (s+1)
// apply transform
double x2 = tx + x1 * s1 - y1 * rz + z1 * ry;
double y2 = ty + x1 * rz + y1 * s1 - z1 * rx;
double z2 = tz - x1 * ry + y1 * rx + z1 * s1;
// -- convert cartesian to polar coordinates (using ellipse 2)
double a = e2.SemimajorAxis;
double precision = 4 / e2.SemimajorAxis; // results accurate to around 4 metres
eSq = (Math.Pow(e2.SemimajorAxis, 2) - Math.Pow(e2.SemiMinorAxis, 2)) / Math.Pow(e2.SemimajorAxis, 2);
double p = Math.Sqrt(x2 * x2 + y2 * y2);
double phi = Math.Atan2(z2, p * (1 - eSq)), phiP = 2 * Math.PI;
while (Math.Abs(phi - phiP) > precision)
{
nu = a / Math.Sqrt(1 - eSq * Math.Sin(phi) * Math.Sin(phi));
phiP = phi;
phi = Math.Atan2(z2 + eSq * nu * Math.Sin(phi), p);
}
double lambda = Math.Atan2(y2, x2);
H = p / Math.Cos(phi) - nu;
return(new PolarGeoCoordinate(
RadToDeg(phi), RadToDeg(lambda), H, AngleUnit.Degrees, t.outputCoordinateSystem));
}
private static PolarGeoCoordinate Convert(
PolarGeoCoordinate originalCoord, EllipseParameter e1, HelmertTransform t, EllipseParameter e2)
{
// -- convert polar to cartesian coordinates (using ellipse 1)
PolarGeoCoordinate p1 = PolarGeoCoordinate.ChangeUnits(originalCoord, AngleUnit.Radians);
double sinPhi = Math.Sin(p1.Lat);
double cosPhi = Math.Cos(p1.Lat);
double sinLambda = Math.Sin(p1.Lon);
double cosLambda = Math.Cos(p1.Lon);
double H = p1.Height;
double eSq = (Math.Pow(e1.SemimajorAxis, 2) - Math.Pow(e1.SemiMinorAxis, 2)) / Math.Pow(e1.SemimajorAxis, 2);
double nu = e1.SemimajorAxis / Math.Sqrt(1 - eSq * sinPhi * sinPhi);
double x1 = (nu + H) * cosPhi * cosLambda;
double y1 = (nu + H) * cosPhi * sinLambda;
double z1 = ((1 - eSq) * nu + H) * sinPhi;
// -- apply helmert transform using appropriate params
double tx = t.tx, ty = t.ty, tz = t.tz;
double rx = t.rx / 3600 * Math.PI / 180; // normalise seconds to radians
double ry = t.ry / 3600 * Math.PI / 180;
double rz = t.rz / 3600 * Math.PI / 180;
double s1 = t.s / 1e6 + 1; // normalise ppm to (s+1)
// apply transform
double x2 = tx + x1 * s1 - y1 * rz + z1 * ry;
double y2 = ty + x1 * rz + y1 * s1 - z1 * rx;
double z2 = tz - x1 * ry + y1 * rx + z1 * s1;
// -- convert cartesian to polar coordinates (using ellipse 2)
double a = e2.SemimajorAxis;
double precision = 4 / e2.SemimajorAxis; // results accurate to around 4 metres
eSq = (Math.Pow(e2.SemimajorAxis, 2) - Math.Pow(e2.SemiMinorAxis, 2)) / Math.Pow(e2.SemimajorAxis, 2);
double p = Math.Sqrt(x2 * x2 + y2 * y2);
double phi = Math.Atan2(z2, p * (1 - eSq)), phiP = 2 * Math.PI;
while (Math.Abs(phi - phiP) > precision)
{
nu = a / Math.Sqrt(1 - eSq * Math.Sin(phi) * Math.Sin(phi));
phiP = phi;
phi = Math.Atan2(z2 + eSq * nu * Math.Sin(phi), p);
}
double lambda = Math.Atan2(y2, x2);
H = p / Math.Cos(phi) - nu;
return new PolarGeoCoordinate(
RadToDeg(phi), RadToDeg(lambda), H, AngleUnit.Degrees, t.outputCoordinateSystem);
}
