cds.healpix

Interface Projection

All Known Implementing Classes:

Healpix

public interface Projection

Define a projection of spherical coordinates (in the unit sphere) to the Euclidean plane, together with the reverse operation. Remark: we use arrays instead of objects because HEALPix is a low level library focused on performances. Accessing an element in an array is faster than accessing a class attribute.

Author:

F.-X. Pineau

Field Summary

Fields

Modifier and Type	Field and Description
static int	LAT_INDEX Index of the lattitude in the array containing the result of an unproject method.
static int	LON_INDEX Index of the longitude in the array containing the result of an unproject method.
static int	X_INDEX Index of the x coordinate in the array containing the result of a project method.
static int	Y_INDEX Index of the y coordinate in the array containing the result of a project method.

Method Summary

Modifier and Type	Method and Description
double[]	project(double lonRad, double latRad) Project the given spherical coordinates into the Euclidean plane.
void	project(double lonRad, double latRad, double[] resultXY) See project(double, double) with the result stored in the given array.
double[]	unproject(double x, double y) Reverse projection: we look for spherical coordinates from their projected coordinates (project(double, double).
void	unproject(double x, double y, double[] resultLonLat) See unproject(double, double) with the result stored in the given array.

Field Detail

LON_INDEX

static final int LON_INDEX

Index of the longitude in the array containing the result of an unproject method.

See Also:

Constant Field Values

LAT_INDEX

static final int LAT_INDEX

Index of the lattitude in the array containing the result of an unproject method.

See Also:

Constant Field Values

X_INDEX

static final int X_INDEX

Index of the x coordinate in the array containing the result of a project method.

See Also:

Constant Field Values

Y_INDEX

static final int Y_INDEX

Index of the y coordinate in the array containing the result of a project method.

See Also:

Constant Field Values

Method Detail

project

double[] project(double lonRad,
                 double latRad)

Project the given spherical coordinates into the Euclidean plane.

Parameters:

lonRad - longitude in radians (the accepted value range is implementation dependent)

latRad - latitude in [-pi/2, pi/2] radians

Returns:

the projection of the given spherical coordinate into the Euclidean plane. The x and y coordinate are stored in the returned array at indices X_INDEX and Y_INDEX respectively. The range of possible value for x and y is implementation dependent.

project

void project(double lonRad,
             double latRad,
             double[] resultXY)

See project(double, double) with the result stored in the given array.

Parameters:

lonRad - see project(double, double)

latRad - see project(double, double)

resultXY - array used to store the result. Must be of size >= 2.

unproject

double[] unproject(double x,
                   double y)

Reverse projection: we look for spherical coordinates from their projected coordinates (project(double, double).

Parameters:

x - the x coordinate of the projected spherical point we are looking for, the accepted value range is implementation dependent

y - the y coordinate of the projected spherical point we are looking for, must be in [-2, 2].

Returns:

the spherical coordinates leading to the given projection coordinates. The lon and lat coordinate are stored in the returned array at indices LON_INDEX and LAT_INDEX respectively. Lat is in [-pi/2, pi/2] radians, lon is also in radians but it possible value range is implementation dependent).

unproject

void unproject(double x,
               double y,
               double[] resultLonLat)

See unproject(double, double) with the result stored in the given array.

Parameters:

x - unproject(double, double)

y - unproject(double, double)

resultLonLat - array used to store the result. Must be of size >= 2.