content/geometry/spheres.cpp


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// Great Circle Distance mit Längen- und Breitengrad.
double gcDist(double pLat, double pLon,
	          double qLat, double qLon, double radius) {
	pLat *= PI / 180; pLon *= PI / 180;
	qLat *= PI / 180; qLon *= PI / 180;
	return radius * acos(cos(pLat) * cos(pLon) *
	                     cos(qLat) * cos(qLon) +
	                     cos(pLat) * sin(pLon) *
	                     cos(qLat) * sin(qLon) +
	                     sin(pLat) * sin(qLat));
}

// Great Circle Distance mit kartesischen Koordinaten.
double gcDist(point p, point q) {
	return acos(p.x * q.x + p.y * q.y + p.z * q.z);
}

// 3D Punkt in kartesischen Koordinaten.
struct point{
	double x, y, z;
	point() {}
	point(double x, double y, double z) : x(x), y(y), z(z) {}
	point(double lat, double lon) {
		lat *= PI / 180.0; lon *= PI / 180.0;
		x = cos(lat) * sin(lon);
		y = cos(lat) * cos(lon);
		z = sin(lat);
	}
};