/// <summary>
/// Computes an angular distance between two points on the unit sphere.
/// </summary>
/// <returns>An angular distance in radians</returns>
public static double AngularDistance(GeoPoint p1, GeoPoint p2)
{
Vector3 v1 = UnitSphere.LatLonToGeocentric(p1.Phi, p1.L);
Vector3 v2 = UnitSphere.LatLonToGeocentric(p2.Phi, p2.L);
return(v1.Angle(v2));
}
/// <summary>
/// Calculates the latitude and longitude points.
/// </summary>
/// <param name="x">X coordinate in the plane of projection</param>
/// <param name="y">Y-coordinate in the plane of projection</param>
/// <param name="lat">Latitude of the</param>
/// <param name="lon">Longitude points</param>
public void Unproject(double x, double y, out double lat, out double lon)
{
Vector3 vector = _center + _xAxis * x + _yAxis * y;
lat = UnitSphere.Latitude(vector);
lon = UnitSphere.Longitude(vector);
}
/// <summary>
/// Calculates the longitude and latitude of the center
/// of projection to the passed values of latitudes and longitudes.
/// </summary>
/// <param name="latLonSequence">Array of real numbers that contains the latitude and longitude
/// (to be completed in the form of a sequence of pairs: "latitude", "longitude")</param>
/// <param name="centerLat">The output value of latitude</param>
/// <param name="centerLon">The output value of the longitude</param>
public static void GetCenter(double[] latLonSequence, out double centerLat, out double centerLon)
{
if (latLonSequence.Length % 2 != 0)
{
throw new ArgumentException("The array should contain an even number of elements", "values");
}
int n = latLonSequence.Length / 2;
double x = 0;
double y = 0;
double z = 0;
for (int i = 0; i < latLonSequence.Length; i += 2)
{
Vector3 v = UnitSphere.LatLonToGeocentric(latLonSequence[i], latLonSequence[i + 1]);
x += v.X / n;
y += v.Y / n;
z += v.Z / n;
}
Vector3 result = new Vector3(x, y, z);
centerLat = UnitSphere.Latitude(result);
centerLon = UnitSphere.Longitude(result);
}
/// <summary>
/// Calculates the coordinates of the point in the projection plane.
/// </summary>
/// <param name="latitude">Latitude of the</param>
/// <param name="longitude">Longitude points</param>
/// <param name="x">X coordinate in the plane of projection</param>
/// <param name="y">Y-coordinate in the plane of projection</param>
public void Project(double latitude, double longitude, out double x, out double y)
{
Vector3 vector = UnitSphere.LatLonToGeocentric(latitude, longitude);
double r = vector * _center;
if (r < 1e-8)
{
throw new ArgumentOutOfRangeException("The point is located too far from the center of projection");
}
vector = vector / r;
x = vector * _xAxis;
y = vector * _yAxis;
}
/// <summary>
/// Instantiates GnommonicProjection.
/// </summary>
/// <param name="centerLongitude">Longitude of projection center</param>
/// <param name="centerLatitude">Latitude of projection center</param>
public GnomonicProjection(double centerLongitude, double centerLatitude)
{
_center = UnitSphere.LatLonToGeocentric(centerLatitude, centerLongitude);
double[] center = { _center.X, _center.Y, _center.Z };
double[] vector = new double[3];
int k = getMinEntryIndex(center);
int j = (k + 2) % 3;
int i = (j + 2) % 3;
vector[i] = -center[j];
vector[j] = center[i];
vector[k] = 0;
_xAxis = (new Vector3(vector[0], vector[1], vector[2])).Unitize();
_yAxis = _center.CrossProduct(_xAxis);
}
