uk.ac.starlink.ttools.cone

Class CdsHealpixUtil

java.lang.Object

uk.ac.starlink.ttools.cone.CdsHealpixUtil

public class CdsHealpixUtil
extends Object

Utilities for working with the cds-healpix-java library in sky plots.

Since:

21 May 2020

Author:

Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static int	DFLT_INTERPOLATE_DEPTH Default minimum interpolation for HEALPix tile edges.

Method Summary

Modifier and Type	Method and Description
static Set<Long>	bmocSet(cds.healpix.HealpixNestedBMOC bmoc) Represents the tiles in a BMOC as a Set of Longs.
static double[]	lonlatToVector(double[] lonlatRad) Converts a longitude, latitude 2-vector to a unit vector suitable for use as a sky surface data position, returning the result as a new array.
static void	lonlatToVector(double[] lonlatRad, double[] xyz) Converts a longitude, latitude 2-vector to a unit vector suitable for use as a sky surface data position, writing the result to a supplied array.
static void	lonlatToVector(double lonRad, double latRad, double[] xyz) Converts a longitude, latitude pair to a unit vector suitable for use as a sky surface data position, writing the result to a supplied array.
static double[][]	lonlatVertices(cds.healpix.VerticesAndPathComputer vpc, long hash, int minDepth) Calculates vertices round the edge of a HEALPix tile, returning the result in a new array.
static int	lonlatVertices(cds.healpix.VerticesAndPathComputer vpc, long hash, int minDepth, double[][] lonlats) Calculates vertices round the edge of a HEALPix tile, writing the result in a supplied array.
static long	vectorToHash(cds.healpix.HashComputer hasher, double[] xyz) Calculates the tile index given a sky surface position unit vector.
static double[]	vectorToLonlat(double[] xyz) Converts a sky surface data position unit vector to a longitude, latitude 2-vector, returning the restult as a new array.
static void	vectorToLonlat(double[] xyz, double[] lonlatRad) Converts a sky surface data position unit vector to a longitude, latitude 2-vector, writing the result to a supplied array.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DFLT_INTERPOLATE_DEPTH

public static final int DFLT_INTERPOLATE_DEPTH

Default minimum interpolation for HEALPix tile edges.

See Also:

Constant Field Values

Method Detail

lonlatToVector

public static void lonlatToVector(double lonRad,
                                  double latRad,
                                  double[] xyz)

Converts a longitude, latitude pair to a unit vector suitable for use as a sky surface data position, writing the result to a supplied array. No error checking is done.

Parameters:

lonRad - longitude in radians

latRad - latitude in radians

xyz - 3-element vector into which (x,y,z) is written

lonlatToVector

public static void lonlatToVector(double[] lonlatRad,
                                  double[] xyz)

Converts a longitude, latitude 2-vector to a unit vector suitable for use as a sky surface data position, writing the result to a supplied array. No error checking is done.

Parameters:

lonlatRad - 2-element vector giving (longitude,latitude) in radians

xyz - 3-element vector into which (x,y,z) is written

lonlatToVector

public static double[] lonlatToVector(double[] lonlatRad)

Converts a longitude, latitude 2-vector to a unit vector suitable for use as a sky surface data position, returning the result as a new array. No error checking is done.

Parameters:

lonlatRad - 2-element vector giving (longitude,latitude) in radians

Returns:

3-element unit vector containing (x,y,z)

vectorToHash

public static long vectorToHash(cds.healpix.HashComputer hasher,
                                double[] xyz)

Calculates the tile index given a sky surface position unit vector.

Parameters:

xyz - 3-element unit vector containing (x,y,z)

vectorToLonlat

public static void vectorToLonlat(double[] xyz,
                                  double[] lonlatRad)

Converts a sky surface data position unit vector to a longitude, latitude 2-vector, writing the result to a supplied array. No error checking is done.

Parameters:

xyz - 3-element array containing (x,y,z)

lonlatRad - 2-element array into which (longitude, latitude) in radians is written

vectorToLonlat

public static double[] vectorToLonlat(double[] xyz)

Converts a sky surface data position unit vector to a longitude, latitude 2-vector, returning the restult as a new array. No error checking is done.

Parameters:

xyz - 3-element unit vector containing (x,y,z)

Returns:

2-element array giving (longitude, latitude) in radians

bmocSet

public static Set<Long> bmocSet(cds.healpix.HealpixNestedBMOC bmoc)

Represents the tiles in a BMOC as a Set of Longs. The returned object is a thin adapter on top of the input BMOC.

Parameters:

bmoc - result of healpix query

Returns:

set of hashes at BMOC depth

lonlatVertices

public static int lonlatVertices(cds.healpix.VerticesAndPathComputer vpc,
                                 long hash,
                                 int minDepth,
                                 double[][] lonlats)

Calculates vertices round the edge of a HEALPix tile, writing the result in a supplied array. This convenience method just simplifies the required parameters.

Parameters:

vpc - healpix object that does the work

hash - tile index

minDepth - the minimal depth at which vertices are calculated; if the tile depth is greater or equal to this value then 4 vertices will be calculated, otherwise interpolated points will be included

lonlats - [N][2]-element array into which pairs of (longitude,latitude) in radians will be written

Returns:

number of vertices written into lonlats

lonlatVertices

public static double[][] lonlatVertices(cds.healpix.VerticesAndPathComputer vpc,
                                        long hash,
                                        int minDepth)

Calculates vertices round the edge of a HEALPix tile, returning the result in a new array. This convenience method just simplifies the required parameters.

Parameters:

vpc - healpix object that does the work

hash - tile index

minDepth - the minimal depth at which vertices are calculated; if the tile depth is greater or equal to this value then 4 vertices will be calculated, otherwise interpolated points will be included

Returns:

array of (longitude,latitude) pairs in radians