uk.ac.starlink.table.join
Interface SkyPixellator

All Known Implementing Classes:

HealpixSkyPixellator, HtmSkyPixellator, PixtoolsHealpixSkyPixellator

public interface SkyPixellator

Provides a pixellisation of the celestial sphere. Usually it is necessary to call setScale(double) before an instance of this class can be used.

Since:

5 Sep 2011

Method Summary

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	setScale(double scale) Sets the characteristic angular scale for this pixellator.

Method Detail

setScale

void setScale(double scale)

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.

Parameters:

scale - pixel length scale in radians

getScale

double getScale()

Returns the most recently set angular scale.

Returns:

pixel length scale in radians

getPixels

Object[] getPixels(double alpha,
                   double delta,
                   double radius)

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.

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

getTuningParameter

DescribedValue getTuningParameter()

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).

Returns:

tuning parameter