uk.ac.starlink.table.join

Class AbstractSkyMatchEngine

java.lang.Object

uk.ac.starlink.table.join.AbstractSkyMatchEngine

All Implemented Interfaces:

MatchEngine

Direct Known Subclasses:

EllipseSkyMatchEngine, ErrorSkyMatchEngine, FixedSkyMatchEngine

public abstract class AbstractSkyMatchEngine
extends Object
implements MatchEngine

Abstract superclass for MatchEngines which work on the celestial sphere.

Since:

5 Sep 2011

Author:

Mark Taylor

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractSkyMatchEngine(SkyPixellator pixellator, double scale) Constructor.

Method Summary

Modifier and Type	Method and Description
static double	calculateSeparation(double alpha1, double delta1, double alpha2, double delta2) Returns the distance along a great circle between two points.
SkyPixellator	getPixellator() Returns this object's pixellator.
protected double	getScale() Returns the length scale used for sky pixellisation.
DescribedValue[]	getTuningParameters() Returns a set of DescribedValue objects whose values can be modified to tune the performance of the match.
static boolean	isSkyPosition(double alpha, double delta) Indicates whether a (longitude, latitude) pair can be interpreted as a legal position on the sky.
protected void	setScale(double scale) Sets the length scale used for sky pixellisation.
abstract String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface uk.ac.starlink.table.join.MatchEngine

createCoverageFactory, createMatchKitFactory, getMatchParameters, getMatchScoreInfo, getScoreScale, getTupleInfos

Constructor Detail

AbstractSkyMatchEngine

protected AbstractSkyMatchEngine(SkyPixellator pixellator,
                                 double scale)

Constructor.

Parameters:

pixellator - handles sky pixellisation

scale - initial length scale for pixels, in radians

Method Detail

setScale

protected void setScale(double scale)

Sets the length scale used for sky pixellisation.

Parameters:

scale - pixel length scale in radians

getScale

protected double getScale()

Returns the length scale used for sky pixellisation.

Returns:

pixel length scale in radians

getTuningParameters

public DescribedValue[] getTuningParameters()

Description copied from interface: MatchEngine

Returns a set of DescribedValue objects whose values can be modified to tune the performance of the match. This match engine's performance can be influenced by calling DescribedValue.setValue(java.lang.Object) on the returned objects.

Changing these values will make no difference to the output of MatchKit.matchScore(java.lang.Object[], java.lang.Object[]), but may change the output of MatchKit.getBins(java.lang.Object[]). This may change the CPU and memory requirements of the match, but will not change the result. The default value should be something sensible, so that setting the value of these parameters is not in general required.

Specified by:

getTuningParameters in interface MatchEngine

Returns:

array of described values which may influence match performance

getPixellator

public SkyPixellator getPixellator()

Returns this object's pixellator.

Returns:

pixellator

toString

public abstract String toString()

Overrides:

toString in class Object

calculateSeparation

public static double calculateSeparation(double alpha1,
                                         double delta1,
                                         double alpha2,
                                         double delta2)

Returns the distance along a great circle between two points.

Parameters:

alpha1 - right ascension of point 1 in radians

delta1 - declination of point 1 in radians

alpha2 - right ascension of point 2 in radians

delta2 - declination of point 2 in radians

Returns:

angular separation of point 1 and point 2 in radians

isSkyPosition

public static boolean isSkyPosition(double alpha,
                                    double delta)

Indicates whether a (longitude, latitude) pair can be interpreted as a legal position on the sky.

Parameters:

alpha - longitude in radians

delta - latitude in radians

Returns:

true iff alpha is a finite real number and delta is in the range -PI/2<=delta<=PI/2