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java.lang.Objectuk.ac.starlink.table.join.SkyMatchEngine
uk.ac.starlink.table.join.HEALPixMatchEngine
public class HEALPixMatchEngine
SkyMatchEngine implementation which works using the HEALPix pixelisation scheme. This works better than the HTM-based one for two reasons:
This implementation is based on the PixTools Java HEALPix classes written by Nickolai Kouropatkine at Fermilab.
Field Summary |
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Fields inherited from interface uk.ac.starlink.table.join.MatchEngine |
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NO_BINS |
Constructor Summary | |
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HEALPixMatchEngine(double separation,
boolean useErrors)
Constructs a new match engine which considers two points (RA,Dec tuples) to match if they are within a given angular distance on the celestial sphere. |
Method Summary | |
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int |
calculateDefaultK(double sep)
Determines a default value to use for the HEALPix k parameter based on a given separation. |
protected java.lang.Object[] |
getBins(double ra,
double dec,
double err)
Returns a set of keys for bins into which possible matches for a given sky position, with a given error, might fall. |
int |
getHealpixK()
Returns the HEALPix k value, which determines sky pixel size, equivalent to log2(nside). |
DescribedValue[] |
getTuningParameters()
Returns a set of DescribedValue objects whose values can be modified to tune the performance of the match. |
void |
setHealpixK(int healpixK)
Sets the HEALPix k value, which determines sky pixel size, equivalent to log2(nside). |
void |
setSeparation(double separation)
Configures this match engine to consider two points (RA,Dec tuples) to match if they are within a given angular distance on the celestial sphere. |
Methods inherited from class uk.ac.starlink.table.join.SkyMatchEngine |
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calculateSeparation, canBoundMatch, getBins, getMatchBounds, getMatchParameters, getMatchScoreInfo, getSeparation, getTupleInfos, getUseErrors, matchScore, setUseErrors, toString |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public HEALPixMatchEngine(double separation, boolean useErrors)
separation
- match radius in radiansuseErrors
- if true, per-row errors can be specified as
a third element of the tuples; otherwise only the fixed
separation value countsMethod Detail |
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public void setSeparation(double separation)
SkyMatchEngine
setSeparation
in class SkyMatchEngine
separation
- match radius in radiansprotected java.lang.Object[] getBins(double ra, double dec, double err)
SkyMatchEngine
equals
and hashCode
methods
implemented properly for comparison.
The err
value will not be greater than the current
result of getSeparation
.
getBins
in class SkyMatchEngine
ra
- right ascension of point to test (radians)dec
- declination of point to test (radians)err
- possible distance away from given location of matchSkyMatchEngine.getBins(java.lang.Object[])
public DescribedValue[] getTuningParameters()
MatchEngine
DescribedValue.setValue(java.lang.Object)
on the
returned objects.
Changing these values will make no difference to the output of
MatchEngine.matchScore(java.lang.Object[], java.lang.Object[])
, but may change the output of MatchEngine.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.
public void setHealpixK(int healpixK)
healpixK
- new k valuepublic int getHealpixK()
public int calculateDefaultK(double sep)
sep
- max sky separation angle for a match, in radians
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Copyright © 2004 CLRC: Central Laboratory of the Research Councils. All rights reserved. | ||||||||
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