/**
* Projects a point from the surface of a sphere onto this projector's plane. The units of the
* output coordinates are radians, or at least radian-like. In the case of a projection error,
* the returned coordinates will be NaNs.
*
* @param alpha RA of point to be projected
* @param delta Dec of point to be projected
* @return (x,y) Cartesian coordinates of projected point
*/
public double[] project(double alpha, double delta) {
try {
AngleDR ad = pal_.Ds2tp(new AngleDR(alpha, delta), ad0_);
return new double[] {ad.getAlpha(), ad.getDelta()};
} catch (palError e) {
return new double[] {Double.NaN, Double.NaN};
}
}
/**
* Find a point midway between two given points.
*
* @param alpha1 RA of point 1
* @param delta1 Dec of point 1
* @param alpha2 RA of point 2
* @param delta2 Dec of point 2
* @return (ra,dec) for bisector point
*/
static double[] bisect(double alpha1, double delta1, double alpha2, double delta2) {
double[] p1 = pal_.Dcs2c(new AngleDR(alpha1, delta1));
double[] p2 = pal_.Dcs2c(new AngleDR(alpha2, delta2));
double[] pc =
new double[] {(p1[0] + p2[0]) * 0.5, (p1[1] + p2[1]) * 0.5, (p1[2] + p2[2]) * 0.5};
AngleDR cSph = pal_.Dcc2s(pc);
return new double[] {cSph.getAlpha(), cSph.getDelta()};
}
/**
* Takes a point on the tangent plane and works out where it would be on the surface of the
* sphere.
*
* @param x X coordinate of projected point
* @param y Y coordinate of projected point
* @return (alpha, delta) coordinates of point that projects to (x,y)
*/
public double[] unproject(double x, double y) {
AngleDR ad = pal_.Dtp2s(new AngleDR(x, y), ad0_);
return new double[] {ad.getAlpha(), ad.getDelta()};
}