uk.ac.starlink.ttools.cone

Class HealpixTiling

java.lang.Object

uk.ac.starlink.ttools.cone.HealpixTiling

All Implemented Interfaces:

SkyTiling

public class HealpixTiling
extends Object
implements SkyTiling

Tiling implementation based on the HEALPix scheme.

Since:

12 Dec 2007

Author:

Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_LEVEL Maximum healpix level permitted by CDS Healpix implementation (29).

Constructor Summary

Constructors

Constructor and Description
HealpixTiling(int k, boolean nest) Constructor.

Method Summary

Modifier and Type	Method and Description
int	getHealpixK() Returns the HEALpix level.
ValueInfo	getIndexInfo() Returns a metadata item suitable for describing the pixel index used by this tiling.
long	getPixelCount() Returns the total number of tiles in this tiling.
long	getPositionTile(double ra, double dec) Returns the index of the tile in which a given sky position falls.
long[]	getTileRange(double ra, double dec, double radius) Returns the bounds of a range of pixels which is known to cover a given cone on the sky.
boolean	isNest() Indicates HEALPix ordering scheme.

Methods inherited from class java.lang.Object

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

Field Detail

MAX_LEVEL

public static final int MAX_LEVEL

Maximum healpix level permitted by CDS Healpix implementation (29).

See Also:

Constant Field Values

Constructor Detail

HealpixTiling

public HealpixTiling(int k,
                     boolean nest)

Constructor.

Parameters:

k - Healpix level

nest - true for nesting scheme, false for ring scheme

Method Detail

getHealpixK

public int getHealpixK()

Returns the HEALpix level.

Returns:

log2(nside)

isNest

public boolean isNest()

Indicates HEALPix ordering scheme.

Returns:

true for NEST, false for RING

getPixelCount

public long getPixelCount()

Description copied from interface: SkyTiling

Returns the total number of tiles in this tiling. Tile indices are assumed to be in the range from zero (inclusive) to this value (exclusive), so the returned value is one greater than the maximum tile index.

Specified by:

getPixelCount in interface SkyTiling

Returns:

pixel count

getIndexInfo

public ValueInfo getIndexInfo()

Description copied from interface: SkyTiling

Returns a metadata item suitable for describing the pixel index used by this tiling.

Specified by:

getIndexInfo in interface SkyTiling

Returns:

tile index metadata

getPositionTile

public long getPositionTile(double ra,
                            double dec)

Description copied from interface: SkyTiling

Returns the index of the tile in which a given sky position falls.

Specified by:

getPositionTile in interface SkyTiling

Parameters:

ra - right ascension in degrees

dec - declination in degrees

Returns:

tile index for position

getTileRange

public long[] getTileRange(double ra,
                           double dec,
                           double radius)

Description copied from interface: SkyTiling

Returns the bounds of a range of pixels which is known to cover a given cone on the sky. The return value is a two-element array, (lo,hi). Every point in the specified cone must have a tile index which is greater than or equal to the first element of that array, and less than or equal to the second element. If the question cannot be answered, or if the range is thought to be too large to be of use (for instance, if it would take a long time to calculate), then null may be returned.

Specified by:

getTileRange in interface SkyTiling

Parameters:

ra - right ascension in degrees

dec - declination in degrees

radius - radius in degrees

Returns:

2-element array giving inclusive (low, high) bounds of tile range covering the cone