/**
* Forward project a point. If the point is not within the viewable hemisphere, return flags in
* AzimuthVar variable if specified.
*
* @param phi double latitude in radians
* @param lambda double longitude in radians
* @param p Point2D
* @param azVar AzimuthVar or null
* @return Point2D pt
*/
protected Point2D _forward(double phi, double lambda, Point2D p, AzimuthVar azVar) {
double c = hemisphere_distance(centerY, centerX, phi, lambda);
// normalize invalid point to the edge of the sphere
if (c > HEMISPHERE_EDGE) {
double az = GreatCircle.sphericalAzimuth(centerY, centerX, phi, lambda);
if (azVar != null) {
azVar.invalid_forward = true; // set the invalid
// flag
azVar.current_azimuth = (float) az; // record azimuth
// of this
// point
}
return edge_point(p, az);
}
double kPrime = 1 / Math.cos(c);
double cosPhi = Math.cos(phi);
double sinPhi = Math.sin(phi);
double lambdaMinusCtrLon = lambda - centerX;
double cosLambdaMinusCtrLon = Math.cos(lambdaMinusCtrLon);
double sinLambdaMinusCtrLon = Math.sin(lambdaMinusCtrLon);
double x = (scaled_radius * kPrime * cosPhi * sinLambdaMinusCtrLon) + wx;
double y =
hy
- (scaled_radius
* kPrime
* (cosCtrLat * sinPhi - sinCtrLat * cosPhi * cosLambdaMinusCtrLon));
p.setLocation(x, y);
return p;
}
// Examples of distances and directions calculations
public static void main(String[] args) {
GeoPoint from = new GeoPoint(37.501282801564244, -122.48082160949707); // the boat
GeoPoint to = new GeoPoint(37.49403906867881, -122.48468399047852); // HMB Entrance
double dist = from.gcDistanceBetween(to);
double heading =
GreatCircle.calculateRhumLineRoute(from.degreesToRadians(), to.degreesToRadians());
dist = GreatCircle.calculateRhumLineDistance(from.degreesToRadians(), to.degreesToRadians());
System.out.println(
"Loxo Dist:" + dist + " nm, " + (dist * 1852) + " m, heading " + Math.toDegrees(heading));
GreatCircle gc = new GreatCircle();
gc.setStartInDegrees(from);
gc.setArrivalInDegrees(to);
gc.calculateGreatCircle(10);
dist = Math.toDegrees(gc.getDistance()) * 60;
GreatCircleWayPoint first = gc.getRoute().get(1);
heading = first.getZ().doubleValue();
System.out.println("Ortho Dist:" + dist + " nm, " + (dist * 1852) + " m, heading " + heading);
}
/**
* Calculate point along edge of hemisphere (using center point and current azimuth).
*
* <p>This is invoked for points that aren't visible in the current hemisphere.
*
* @param p Point2D
* @return Point2D p
*/
private Point2D edge_point(Point2D p, double current_azimuth) {
double c = HEMISPHERE_EDGE;
LatLonPoint tmpll =
GreatCircle.sphericalBetween(centerY, centerX, c /*-epsilon*/, current_azimuth);
double phi = tmpll.getRadLat();
double lambda = tmpll.getRadLon();
double kPrime = 1f / Math.cos(c);
double cosPhi = Math.cos(phi);
double sinPhi = Math.sin(phi);
double lambdaMinusCtrLon = lambda - centerY;
double cosLambdaMinusCtrLon = Math.cos(lambdaMinusCtrLon);
double sinLambdaMinusCtrLon = Math.sin(lambdaMinusCtrLon);
double x = (scaled_radius * kPrime * cosPhi * sinLambdaMinusCtrLon) + wx;
double y =
hy
- (scaled_radius
* kPrime
* (cosCtrLat * sinPhi - sinCtrLat * cosPhi * cosLambdaMinusCtrLon));
p.setLocation(x, y);
return p;
}
public static final boolean hemisphere_clip(
double phi1, double lambda0, double phi, double lambda) {
return (GreatCircle.sphericalDistance(phi1, lambda0, phi, lambda) /*-epsilon*/
<= HEMISPHERE_EDGE);
}
public static final double hemisphere_distance(
double phi1, double lambda0, double phi, double lambda) {
return GreatCircle.sphericalDistance(phi1, lambda0, phi, lambda) /*-epsilon*/;
}
/**
* Get the distance c of the point from the center of the hemisphere.
*
* @param phi1 latitude
* @param lambda0 longitude
* @param phi latitude
* @param lambda longitude
* @return float c angular distance in radians
*/
public static final float hemisphere_distance(
float phi1, float lambda0, float phi, float lambda) {
return GreatCircle.sphericalDistance(phi1, lambda0, phi, lambda) /*-epsilon*/;
}