public override Point PointOnBearing(Point from, double distDEG, double bearingDEG, SpatialContext ctx, Point reuse)
{
if (distDEG == 0)
{
if (reuse == null)
return from;
reuse.Reset(from.GetX(), from.GetY());
return reuse;
}
double bearingRAD = DistanceUtils.ToRadians(bearingDEG);
double x = from.GetX() + Math.Sin(bearingRAD)*distDEG;
double y = from.GetY() + Math.Cos(bearingRAD)*distDEG;
if (reuse == null)
{
return ctx.MakePoint(x, y);
}
else
{
reuse.Reset(x, y);
return reuse;
}
}
/**
* Given a start point (startLat, startLon) and a bearing on a sphere of radius <i>sphereRadius</i>, return the destination point.
*
*
* @param startLat The starting point latitude, in radians
* @param startLon The starting point longitude, in radians
* @param distanceRAD The distance to travel along the bearing in radians.
* @param bearingRAD The bearing, in radians. North is a 0, moving clockwise till radians(360).
* @param result A preallocated array to hold the results. If null, a new one is constructed.
* @return The destination point, in radians. First entry is latitude, second is longitude
*/
public static Point PointOnBearingRAD(double startLat, double startLon, double distanceRAD, double bearingRAD, SpatialContext ctx, Point reuse)
{
/*
lat2 = asin(sin(lat1)*cos(d/R) + cos(lat1)*sin(d/R)*cos(θ))
lon2 = lon1 + atan2(sin(θ)*sin(d/R)*cos(lat1), cos(d/R)−sin(lat1)*sin(lat2))
*/
double cosAngDist = Math.Cos(distanceRAD);
double cosStartLat = Math.Cos(startLat);
double sinAngDist = Math.Sin(distanceRAD);
double sinStartLat = Math.Sin(startLat);
double lat2 = Math.Asin(sinStartLat*cosAngDist +
cosStartLat*sinAngDist*Math.Cos(bearingRAD));
double lon2 = startLon + Math.Atan2(Math.Sin(bearingRAD)*sinAngDist*cosStartLat,
cosAngDist - sinStartLat*Math.Sin(lat2));
// normalize lon first
if (lon2 > DEG_180_AS_RADS)
{
lon2 = -1.0*(DEG_180_AS_RADS - (lon2 - DEG_180_AS_RADS));
}
else if (lon2 < -DEG_180_AS_RADS)
{
lon2 = (lon2 + DEG_180_AS_RADS) + DEG_180_AS_RADS;
}
// normalize lat - could flip poles
if (lat2 > DEG_90_AS_RADS)
{
lat2 = DEG_90_AS_RADS - (lat2 - DEG_90_AS_RADS);
if (lon2 < 0)
{
lon2 = lon2 + DEG_180_AS_RADS;
}
else
{
lon2 = lon2 - DEG_180_AS_RADS;
}
}
else if (lat2 < -DEG_90_AS_RADS)
{
lat2 = -DEG_90_AS_RADS - (lat2 + DEG_90_AS_RADS);
if (lon2 < 0)
{
lon2 = lon2 + DEG_180_AS_RADS;
}
else
{
lon2 = lon2 - DEG_180_AS_RADS;
}
}
if (reuse == null)
{
return ctx.MakePoint(lon2, lat2);
}
else
{
reuse.Reset(lon2, lat2); //x y
return reuse;
}
}
public override Point PointOnBearing(Point @from, double distDEG, double bearingDEG, SpatialContext ctx, Point reuse)
{
if (distDEG == 0)
{
if (reuse == null)
return from;
reuse.Reset(from.GetX(), from.GetY());
return reuse;
}
Point result = DistanceUtils.PointOnBearingRAD(
DistanceUtils.ToRadians(from.GetY()), DistanceUtils.ToRadians(from.GetX()),
DistanceUtils.ToRadians(distDEG),
DistanceUtils.ToRadians(bearingDEG), ctx, reuse);//output result is in radians
result.Reset(DistanceUtils.ToDegrees(result.GetX()), DistanceUtils.ToDegrees(result.GetY()));
return result;
}
