uk.ac.starlink.table.join
Class HTMMatchEngine

java.lang.Object
  |
  +--uk.ac.starlink.table.join.SkyMatchEngine
        |
        +--uk.ac.starlink.table.join.HTMMatchEngine
All Implemented Interfaces:
MatchEngine

public class HTMMatchEngine
extends SkyMatchEngine

Implements the object matching interface for sky coordinates using the HTM (Hierarchical Triangular Mesh) pixel-indexing scheme.

Note that the HEALPixMatchEngine implementation normally gives much faster matching than this and should generally be used in preference.

See Also:
http://www.sdss.jhu.edu/htm/doc

Field Summary
static double MESH_SCALE
          Scaling factor which determines the size of the mesh cells used as a multiple of the size of the separation.
 
Fields inherited from interface uk.ac.starlink.table.join.MatchEngine
NO_BINS
 
Constructor Summary
HTMMatchEngine(double separation)
          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
 Object[] getBins(Object[] radec)
          Returns all the HTM cells which fall wholly or partially within separation radians of a given position.
 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
canBoundMatch, getMatchBounds, getMatchParameters, getSeparation, getTupleInfos, matchScore, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

MESH_SCALE

public static final double MESH_SCALE
Scaling factor which determines the size of the mesh cells used as a multiple of the size of the separation. It can be used as a tuning parameter. It must be >1.

See Also:
Constant Field Values
Constructor Detail

HTMMatchEngine

public HTMMatchEngine(double separation)
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.

Parameters:
separation - match radius in radians
Method Detail

setSeparation

public void setSeparation(double separation)
Description copied from class: SkyMatchEngine
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.

Overrides:
setSeparation in class SkyMatchEngine
Parameters:
separation - match radius in radians

getBins

public Object[] getBins(Object[] radec)
Returns all the HTM cells which fall wholly or partially within separation radians of a given position.

Parameters:
radec - 2-element array of Number objects giving RA & Dec of the position to test
Returns:
set of bin keys which might be returned by invoking this method on other tuples which count as matches for the submitted tuple

Copyright © 2004 CLRC: Central Laboratory of the Research Councils. All rights reserved.