static HelmertTransform()
{
WGS84toAiry1830 = new HelmertTransform(-446.448, 124.157, -542.060,
-0.1502, -0.2470, -0.8421,
20.4894);
Airy1830toWGS84 = new HelmertTransform(446.448, -124.157, 542.060,
0.1502, 0.2470, 0.8421,
-20.4894);
}
private LatLng ChangeDatum(Ellipsoid currentEllipsoid, HelmertTransform transform, Ellipsoid targetEllipsoid)
{
// This is deliberately ugly C#. It's ported from javascript at http://www.jstott.me.uk/jscoord/ (v1.1.1)
// The less I touch it, the less chance there is of breaking it.
var a = currentEllipsoid.a;
var b = currentEllipsoid.b;
var eSquared = currentEllipsoid.eSquared;
var phi = DegreesToRadians(_latitude);
var lambda = DegreesToRadians(_longitude);
var v = a / (Math.Sqrt(1 - eSquared * SinSquared(phi)));
var H = 0.0; // height
var x = (v + H) * Math.Cos(phi) * Math.Cos(lambda);
var y = (v + H) * Math.Cos(phi) * Math.Sin(lambda);
var z = ((1 - eSquared) * v + H) * Math.Sin(phi);
var tx = transform._tx;
var ty = transform._ty;
var tz = transform._tz;
var s = transform._s;
var rx = transform._rx;
var ry = transform._ry;
var rz = transform._rz;
var xB = tx + (x * (1 + s)) + (-rx * y) + (ry * z);
var yB = ty + (rz * x) + (y * (1 + s)) + (-rx * z);
var zB = tz + (-ry * x) + (rx * y) + (z * (1 + s));
a = targetEllipsoid.a;
b = targetEllipsoid.b;
eSquared = targetEllipsoid.eSquared;
var lambdaB = RadiansToDegrees(Math.Atan(yB / xB));
var p = Math.Sqrt((xB * xB) + (yB * yB));
var phiN = Math.Atan(zB / (p * (1 - eSquared)));
for (var i = 1; i < 10; i++)
{
v = a / (Math.Sqrt(1 - eSquared * SinSquared(phiN)));
var phiN1 = Math.Atan((zB + (eSquared * v * Math.Sin(phiN))) / p);
phiN = phiN1;
}
var phiB = RadiansToDegrees(phiN);
LatLng result = new LatLng(phiB, lambdaB);
return(result);
}
