HtmSkyPixellator (Starjava Table API)

java.lang.Object
- uk.ac.starlink.table.join.HtmSkyPixellator

All Implemented Interfaces:

SkyPixellator
```
public class HtmSkyPixellator
extends java.lang.Object
implements SkyPixellator
```
Implements sky pixellisation using the HTM (Hierarchical Triangular Mesh) indexing scheme.
Note that the HealpixSkyPixellator implementation normally gives much faster matching than this and should generally be used in preference.

Author:

Mark Taylor (Starlink)

See Also:

http://www.skyserver.org/htm/doc/java/index.html

Constructor Summary

Constructors
Constructor Description

HtmSkyPixellator()
Constructor.

Constructors
Constructor	Description
`HtmSkyPixellator()`	Constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`int`	`calculateDefaultLevel(double scale)`	Determines a default value to use for the level paramer based on a given scale.
`int`	`getLevel()`	Returns the HTM level, which determines sky pixel size.
`java.lang.Object[]`	`getPixels(double alpha, double delta, double radius)`	Returns an array of objects representing pixels in a given region.
`double`	`getScale()`	Returns the most recently set angular scale.
`DescribedValue`	`getTuningParameter()`	Returns a parameter whose value may be adjusted to alter the pixellisation scale.
`void`	`setLevel(int level)`	Sets the HTM level value, which determines sky pixel size.
`void`	`setScale(double scale)`	Sets the characteristic angular scale for this pixellator.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - HtmSkyPixellator
```
public HtmSkyPixellator()
```
    Constructor.
- Method Detail
  - setScale
```
public void setScale(double scale)
```
    Description copied from interface: SkyPixellator
    
    Sets the characteristic angular scale for this pixellator. Pixels should be approximately the size given, so that a larger scale corresponds to larger pixel sizes. The details of pixel size are determined by the details of the pixellation scheme however.
    
    Specified by:
    
    setScale in interface SkyPixellator
    
    Parameters:
    
    scale - pixel length scale in radians
  - getScale
```
public double getScale()
```
    Description copied from interface: SkyPixellator
    
    Returns the most recently set angular scale.
    
    Specified by:
    
    getScale in interface SkyPixellator
    
    Returns:
    
    pixel length scale in radians
  - getTuningParameter
```
public DescribedValue getTuningParameter()
```
    Description copied from interface: SkyPixellator
    
    Returns a parameter whose value may be adjusted to alter the pixellisation scale. This is not necessarily the same as the scale attribute (its value need not be an angle).
    
    Specified by:
    
    getTuningParameter in interface SkyPixellator
    
    Returns:
    
    tuning parameter
  - getPixels
```
public java.lang.Object[] getPixels(double alpha,
                                    double delta,
                                    double radius)
```
    Description copied from interface: SkyPixellator
    
    Returns an array of objects representing pixels in a given region. The parameters specify a small circle on the sphere; any pixels which overlap this circle must be returned (additional pixels may also be returned). The output objects are of some opaque type, but must implement the equals and hashCode methods appropriately, so that objects returned from one call can be compared for identity with objects returned from a subsequent call. This comparability is only guaranteed to work if the pixel scale is not changed in between calls.
    
    Specified by:
    
    getPixels in interface SkyPixellator
    
    Parameters:
    
    alpha - right ascension of circle centre in radians
    
    delta - declination of circle centre in radians
    
    radius - radius of circle in radians
    
    Returns:
    
    array of opaque but comparable pixel objects
  - setLevel
```
public void setLevel(int level)
```
    Sets the HTM level value, which determines sky pixel size. May be in the range 0 (90deg) to 24 (0.01"). If set to -1, a suitable value will be used based on the scale.
    
    Parameters:
    
    level - new level value
  - getLevel
```
public int getLevel()
```
    Returns the HTM level, which determines sky pixel size. The returned value may be the result of a default determination based on scale if no explicit level has been set hitherto, and a non-zero scale is available.
    
    Returns:
    
    level level value used by this engine
  - calculateDefaultLevel
```
public int calculateDefaultLevel(double scale)
```
    Determines a default value to use for the level paramer based on a given scale.
    
    Parameters:
    
    scale - sky distance scale angle, in radians

Class HtmSkyPixellator

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

HtmSkyPixellator

Method Detail

setScale

getScale

getTuningParameter

getPixels

setLevel

getLevel

calculateDefaultLevel