private static DirectResult Direct(double lat1, double lon1, double crs12, double d12)
{
const double eps = 0.00000000005;
double lon;
if ((MathEx.Abs(MathEx.Cos(lat1)) < eps) && !(MathEx.Abs(MathEx.Sin(crs12)) < eps))
{
throw new ArgumentException("Only N-S courses are meaningful, starting at a pole!");
}
double lat = MathEx.Asin(MathEx.Sin(lat1) * MathEx.Cos(d12) +
MathEx.Cos(lat1) * MathEx.Sin(d12) * MathEx.Cos(crs12));
if (MathEx.Abs(MathEx.Cos(lat)) < eps)
{
lon = 0.0; //endpoint a pole
}
else
{
double dlon = MathEx.Atan2(MathEx.Sin(crs12) * MathEx.Sin(d12) * MathEx.Cos(lat1),
MathEx.Cos(d12) - MathEx.Sin(lat1) * MathEx.Sin(lat));
lon = Mod(lon1 - dlon + MathEx.PI, 2 * MathEx.PI) - MathEx.PI;
}
DirectResult outValue = new DirectResult {
_lat = lat, _lon = lon
};
return(outValue);
}
private GeoLatLng ComputeFormDir(GeoLatLng pt1, double distance, double crs)
{
//get select values
double lat2, lon2;
/* Input and validate data */
double lat1 = pt1.LatRadians();
double lon1 = -pt1.LngRadians();
double d12 = distance;
double dc = _currentUnit == UNIT_NM ? 1 : 1.852;
d12 /= dc;
double crs12 = crs * MathEx.PI / 180.0;
if (_currentEarthMode == EARTH_MODEL_SPHERE)
{
// spherical code
d12 /= (180 * 60 / MathEx.PI); // in radians
DirectResult cd = Direct(lat1, lon1, crs12, d12);
lat2 = cd._lat * (180 / MathEx.PI);
lon2 = cd._lon * (180 / MathEx.PI);
}
else
{
// elliptic code// ellipse uses East negative
DirectResult cde = DirectEll(lat1, -lon1, crs12, d12, _currentEarthMode);
lat2 = cde._lat * (180 / MathEx.PI);
lon2 = -cde._lon * (180 / MathEx.PI);// ellipse uses East negative
}
double retLat = lat2;
double retLon = -lon2;
return(new GeoLatLng(retLat, retLon));
}
private static DirectResult DirectEll(double glat1, double glon1, double faz, double s, int ellipse)
{
// glat1 initial geodetic latitude in radians N positive
// glon1 initial geodetic longitude in radians E positive
// faz forward azimuth in radians
// s Distance in units of a (=nm)
const double eps = 0.00000000005;
double b;
double sy = 0, cy = 0, cz = 0, e = 0;
if ((MathEx.Abs(MathEx.Cos(glat1)) < eps) && !(MathEx.Abs(MathEx.Sin(faz)) < eps))
{
throw new ArgumentException("Only N-S courses are meaningful, starting at a pole!");
}
double a = EarthModel[ellipse][0];
double f = 1 / EarthModel[ellipse][1];
double r = 1 - f;
double tu = r * MathEx.Tan(glat1);
double sf = MathEx.Sin(faz);
double cf = MathEx.Cos(faz);
if (cf == 0)
{
b = 0.0;
}
else
{
b = 2.0 * Atan2(tu, cf);
}
double cu = 1.0 / MathEx.Sqrt(1 + tu * tu);
double su = tu * cu;
double sa = cu * sf;
double c2A = 1 - sa * sa;
double x = 1.0 + MathEx.Sqrt(1.0 + c2A * (1.0 / (r * r) - 1.0));
x = (x - 2.0) / x;
double c = 1.0 - x;
c = (x * x / 4.0 + 1.0) / c;
double d = (0.375 * x * x - 1.0) * x;
tu = s / (r * a * c);
double y = tu;
c = y + 1;
while (MathEx.Abs(y - c) > eps)
{
sy = MathEx.Sin(y);
cy = MathEx.Cos(y);
cz = MathEx.Cos(b + y);
e = 2.0 * cz * cz - 1.0;
c = y;
x = e * cy;
y = e + e - 1.0;
y = (((sy * sy * 4.0 - 3.0) * y * cz * d / 6.0 + x) *
d / 4.0 - cz) * sy * d + tu;
}
b = cu * cy * cf - su * sy;
c = r * MathEx.Sqrt(sa * sa + b * b);
d = su * cy + cu * sy * cf;
double glat2 = Modlat(Atan2(d, c));
c = cu * cy - su * sy * cf;
x = Atan2(sy * sf, c);
c = ((-3.0 * c2A + 4.0) * f + 4.0) * c2A * f / 16.0;
d = ((e * cy * c + cz) * sy * c + y) * sa;
double glon2 = Modlon(glon1 + x - (1.0 - c) * d * f);
double baz = Modcrs(Atan2(sa, b) + MathEx.PI);
DirectResult outValue = new DirectResult {_lat = glat2, _lon = glon2, _crs21 = baz};
return outValue;
}
private static DirectResult Direct(double lat1, double lon1, double crs12, double d12)
{
const double eps = 0.00000000005;
double lon;
if ((MathEx.Abs(MathEx.Cos(lat1)) < eps) && !(MathEx.Abs(MathEx.Sin(crs12)) < eps))
{
throw new ArgumentException("Only N-S courses are meaningful, starting at a pole!");
}
double lat = MathEx.Asin(MathEx.Sin(lat1) * MathEx.Cos(d12) +
MathEx.Cos(lat1) * MathEx.Sin(d12) * MathEx.Cos(crs12));
if (MathEx.Abs(MathEx.Cos(lat)) < eps)
{
lon = 0.0; //endpoint a pole
}
else
{
double dlon = MathEx.Atan2(MathEx.Sin(crs12) * MathEx.Sin(d12) * MathEx.Cos(lat1),
MathEx.Cos(d12) - MathEx.Sin(lat1) * MathEx.Sin(lat));
lon = Mod(lon1 - dlon + MathEx.PI, 2 * MathEx.PI) - MathEx.PI;
}
DirectResult outValue = new DirectResult {_lat = lat, _lon = lon};
return outValue;
}
private static DirectResult DirectEll(double glat1, double glon1, double faz, double s, int ellipse)
{
// glat1 initial geodetic latitude in radians N positive
// glon1 initial geodetic longitude in radians E positive
// faz forward azimuth in radians
// s Distance in units of a (=nm)
const double eps = 0.00000000005;
double b;
double sy = 0, cy = 0, cz = 0, e = 0;
if ((MathEx.Abs(MathEx.Cos(glat1)) < eps) && !(MathEx.Abs(MathEx.Sin(faz)) < eps))
{
throw new ArgumentException("Only N-S courses are meaningful, starting at a pole!");
}
double a = EarthModel[ellipse][0];
double f = 1 / EarthModel[ellipse][1];
double r = 1 - f;
double tu = r * MathEx.Tan(glat1);
double sf = MathEx.Sin(faz);
double cf = MathEx.Cos(faz);
if (cf == 0)
{
b = 0.0;
}
else
{
b = 2.0 * Atan2(tu, cf);
}
double cu = 1.0 / MathEx.Sqrt(1 + tu * tu);
double su = tu * cu;
double sa = cu * sf;
double c2A = 1 - sa * sa;
double x = 1.0 + MathEx.Sqrt(1.0 + c2A * (1.0 / (r * r) - 1.0));
x = (x - 2.0) / x;
double c = 1.0 - x;
c = (x * x / 4.0 + 1.0) / c;
double d = (0.375 * x * x - 1.0) * x;
tu = s / (r * a * c);
double y = tu;
c = y + 1;
while (MathEx.Abs(y - c) > eps)
{
sy = MathEx.Sin(y);
cy = MathEx.Cos(y);
cz = MathEx.Cos(b + y);
e = 2.0 * cz * cz - 1.0;
c = y;
x = e * cy;
y = e + e - 1.0;
y = (((sy * sy * 4.0 - 3.0) * y * cz * d / 6.0 + x) *
d / 4.0 - cz) * sy * d + tu;
}
b = cu * cy * cf - su * sy;
c = r * MathEx.Sqrt(sa * sa + b * b);
d = su * cy + cu * sy * cf;
double glat2 = Modlat(Atan2(d, c));
c = cu * cy - su * sy * cf;
x = Atan2(sy * sf, c);
c = ((-3.0 * c2A + 4.0) * f + 4.0) * c2A * f / 16.0;
d = ((e * cy * c + cz) * sy * c + y) * sa;
double glon2 = Modlon(glon1 + x - (1.0 - c) * d * f);
double baz = Modcrs(Atan2(sa, b) + MathEx.PI);
DirectResult outValue = new DirectResult {
_lat = glat2, _lon = glon2, _crs21 = baz
};
return(outValue);
}
