cds.astro
Class Qbox

java.lang.Object
  cds.astro.Qbox

All Implemented Interfaces:

java.io.Serializable

public class Qbox
extends java.lang.Object
implements java.io.Serializable

The Qbox divides the celestial sphere into "cells" of approximative constant size. The routines provided in this module all deal with "qboxes". A qbox is just a number which represents one of the cells.

A qbox number is formed by the values of the projections (X,Y) of the directions on the 6 faces of a cube numbered 1 (z=1), 2 (y=1), 3 (x=1), 4 (x=-1), 5 (y=-1) and 6 (z=-1).

The faces and orientations are defined as:

 
                  +---------+
                  |    ^    |
                  |    |    |
                  |   1+--->|
                  |      x  |
                  |         |
        +---------+---------+---------+---------+
        |    ^    |    ^    |         |         |
        |    |    |    |    |         |         |
        |   5+--->|  3 +--->|   2+--->|   4+--->|
        |      x  |      x  |   x|    |   x|    |
        |         |         |    v    |    v    |
        +---------+---------+---------+---------+
                  |    ^    |
                  |    |x   |
                  |<---+    |
                  |    6    |
                  |         |
                  +---------+
 

Each cube face is divided into 4 areas; each area is further divided into four pieces, etc. The number of valid qboxes is 6×4^N:

   Level    Lower #      qboxes   qbox_size
      0           9           6     83º
      1          36          24     41º
      2         144          96     20º
      3         576         384     10º
      4        2304        1536      5º
      5        9216        6144      2º30'
      6       36864       24576      1º15'
      7      147456       98304        40'
      8      589824      393216        20'
      9     2359296     1572864        10'
     10     9437184     6291456         5'
     11    37748736    25165824         2'30"
     12   150994944   100663296         1'15"
 

where level is a number which can be changed at any time using setLevel(level) method.

The present implementation assumes that level<=12, corresponding to a maximum of 28 bits in the qbox number.

For a level 6, the qbox number is a short integer with bits (from left to right) 1ppp xyxy xyxy xyxy. The leftmost `1' bit allows the recognition of the level; bits p represent the face number (1 to 6), x and y the position, expressed with level bits, along the axises defined above for the face; going one level down in the hierarchy is therefore just a shift of 2 bits and updating the 2 rightmost bits.

The selection of valid qboxes makes usage of an Enumeration which returns the valid qboxes via its nextElement method.

See Also:

Serialized Form

Field Summary

static int

level

Constructor Summary

Qbox()
Define the default Qbox which represents the whole sphere

Qbox(Coo coo)
Define the Qbox containing a given position, at the current level.

Qbox(Qbox qb)
Copy constructor.

Qbox(java.lang.String text)
Define the Qbox from a text similar to the Edited qbox (see toString)

Method Summary

double	area() Compute the area (in square degrees) of a Qbox.
int	box() Actual qbox value as an Integer
Coocube	center() Convert a Qbox into the Coocube position of its center.
static java.util.Enumeration	circle(Coo center, double radius) Return all Qboxes concerned by a Circular Target
boolean	equals(java.lang.Object o) MOD-BB 21-01-04 Ajout de cette methode.
int	face() On which face is located the qbox ?
int	index() Actual qbox index
boolean	isAny() Status of a Qbox: check whether it's completely included in the Selection (no need to make further tests on Position)
int	level() Actual qbox level
static int	level(int b) Compute the level of any integer considered as a qbox
java.util.Enumeration	list() List in an enumeration all Qboxes corresponding to a qbox To get all qboxes, just do the following: cq = new Qbox(); e=cq.list();
static java.util.Enumeration	list(java.util.Vector vector) List in an enumeration all Qboxes selected in a Vector
static double	maxRadius() Return the maximal radius (in degrees) of any Qbox at the default level
static double	minRadius() Return the maximal radius (in degrees) of any Qbox at the default level
double	radius() Compute the radius (in degrees) of the Circle
void	set(Coo c) Convert a Position into its Qbox at the default level
void	set(Coocube cc) Convert a Coocube into a Qbox at the default level
void	set(Qbox qb) Sets the Qbox value from another Qbox object
static int	setLevel(int lev) Change the default Level which is 9.
void	toAny() Set the Qbox to the 'Any' status the Selection (no need to make further tests on Position)
java.lang.String	toString() Default Edition of the Qbox value

Methods inherited from class java.lang.Object

getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

level

public static int level

Constructor Detail

Qbox

public Qbox()

Define the default Qbox which represents the whole sphere

Qbox

public Qbox(Qbox qb)

Copy constructor.

Parameters:

qb - Qbox object to copy

Qbox

public Qbox(Coo coo)

Define the Qbox containing a given position, at the current level.

Parameters:

coo - coordinates object used to create the Qbox

Qbox

public Qbox(java.lang.String text)
     throws java.text.ParseException

Define the Qbox from a text similar to the Edited qbox (see toString)

Parameters:

text - The text to interpret

Throws:

java.text.ParseException - when the text contains invalid characters

Method Detail

setLevel

public static final int setLevel(int lev)

Change the default Level which is 9.

Parameters:

lev - the new level, between 0 and 12 -- other values do not change it.

Returns:

the previously defined level

level

public static final int level(int b)

Compute the level of any integer considered as a qbox

Parameters:

b - the integer considered as a Qbox.

Returns:

the level corresponding to the integer (between -1 and 13)

level

public final int level()

Actual qbox level

Returns:

the level corresponding to the qbox (between -1 and 12)

isAny

public final boolean isAny()

Status of a Qbox: check whether it's completely included in the Selection (no need to make further tests on Position)

Returns:

true if the box is "any"

toAny

public final void toAny()

Set the Qbox to the 'Any' status the Selection (no need to make further tests on Position)

box

public final int box()

Actual qbox value as an Integer

Returns:

a box value (in the range specified in the introduction)

index

public final int index()

Actual qbox index

Returns:

the index, a number between 0 and 6*4^level -1

face

public final int face()

On which face is located the qbox ?

Returns:

the face number, between 1 and 6 -- 0 for whole sphere

set

public final void set(Coocube cc)

Convert a Coocube into a Qbox at the default level

Parameters:

cc - the Coocube equivalent of the position

set

public final void set(Qbox qb)

Sets the Qbox value from another Qbox object

Parameters:

qb - Qbox object to copy

set

public final void set(Coo c)

Convert a Position into its Qbox at the default level

Parameters:

c - the Coocube equivqlent of the position

center

public final Coocube center()

Convert a Qbox into the Coocube position of its center.

maxRadius

public static final double maxRadius()

Return the maximal radius (in degrees) of any Qbox at the default level

Returns:

The maximal radius

minRadius

public static final double minRadius()

Return the maximal radius (in degrees) of any Qbox at the default level

Returns:

The maximal radius

area

public final double area()

Compute the area (in square degrees) of a Qbox. Use the ArcSin formula S = A_0 + A_1 + A_2 + A_3 - 2*pi where A_i are the angles of the rectangle. The formula is especially simple in a tangential projection.

Returns:

The area for the Qbox in square degrees.

radius

public final double radius()

Compute the radius (in degrees) of the Circle

Returns:

The radius of the Qbox

toString

public final java.lang.String toString()

Default Edition of the Qbox value

Overrides:

toString in class java.lang.Object

Returns:

the string equivalent of the coocube the letter 'A' is appended for ANY IN QBOX.

list

public java.util.Enumeration list()

List in an enumeration all Qboxes corresponding to a qbox To get all qboxes, just do the following: cq = new Qbox(); e=cq.list();

Returns:

a list of Qboxes existing at the default level contained in the Object.

list

public static java.util.Enumeration list(java.util.Vector vector)

List in an enumeration all Qboxes selected in a Vector

Parameters:

vector - a Vector of qboxes returned from a select routine

Returns:

an Enumeration of leaf Qboxes.

circle

public static java.util.Enumeration circle(Coo center,
                                           double radius)

Return all Qboxes concerned by a Circular Target

Parameters:

center - the target center

radius - the target radius

Returns:

an Enumeration of leaf Qboxes.

equals

public boolean equals(java.lang.Object o)

MOD-BB 21-01-04 Ajout de cette methode. Test d'egalite de QBox.

Overrides:

equals in class java.lang.Object

Parameters:

o - Object a comparer.

Returns:

Vrai si o est identique a this, faux sinon.