cds.astro
Class Coo

java.lang.Object
  cds.astro.Coo

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

Direct Known Subclasses:

Astrocoo, Coocube

public class Coo
extends java.lang.Object
implements java.io.Serializable, java.lang.Cloneable

Class that manipulates the coordinates defining a point on the celestial sphere. The class includes conversions between polar angles (lon,lat) expressed in degrees, and Cartesian 3-vectors. The typical way of converting between polar and cartesian is:

 Coo aCoo = new Coo ; double u[] = new double[3] ;
 while (true) {
     aCoo.set(stdin.readLine()) ;
     System.out.println("Coordonnees   : " + aCoo) ;
     u[0] = aCoo.x; u[1] = aCoo.y; u[2] = aCoo.z;
     System.out.println("Cos. directeurs: " + Coo.toString(u)) ;
 }
 

This class also deals with 3x3 matrices.

Version:

1.0 : 03-Mar-2000
, 1.1 : 24-Mar-2000: Bug in dist
, 1.2 : 17-Apr-2002: Accept decimal degrees in scientific notation
, 1.3 : 17-Sep-2002: Method "dist" between 2 coordinates
, 1.4 : 21-Jan 2004 (BB): ajout de la methode equals.
, 1.5 : 12-Aug 2004: methods rotate rotate_1 dlon and dlat moved to Astrocoo, 1.6 : 24-Apr-2006: methods moveMatrix, 1.7 : 04-Jun-2006: methods add sub, 1.8 : 02-Feb-2007: editingDecimals

Author:

Pierre Fernique, Francois Ochsenbein [CDS]

See Also:

Serialized Form

Field Summary

static int	decimals Number of decimals edited in the default toString method.
static Editing	ed The edition of Coordinates
static double[][]	Umatrix3 The unit 3-D unit matrix .
double	x Components of unit vector (direction cosines)
double	y Components of unit vector (direction cosines)
double	z Components of unit vector (direction cosines)

Constructor Summary

Coo()
The basic contructor: undefined position

Coo(double lon, double lat)
Define a coordinate from its angles

Coo(double x, double y, double z)
Define a coordinate from its direction cosines.

Coo(java.lang.String text)
Define a coordinate from a string

Method Summary

double	add(double[] du) Addition of a vector (addition, then normalisation)
static double	add(double[] u, double[] du) Addition of a vector (addition, then normalisation)
java.lang.Object	clone() Clone the Coo object
void	copyAngles(double[] o) Get the spherical angles (lon, lat) as a 2-vector
void	copyUvector(double[] u) Get the unit vector (x, y, z) as a 3-vector
double	distance(Coo pos) Distance between 2 points on the sphere.
static double	distance(double lon1, double lat1, double lon2, double lat2) Distance between 2 points on the sphere.
void	dump(java.lang.String title) Dump the contents of a Coordinate
java.lang.StringBuffer	edit(java.lang.StringBuffer b, int nd) Default Edition of the Coordinates, as 2 numbers expressing the angles in degrees.
java.lang.StringBuffer	editCoo(java.lang.StringBuffer b, int nd) Edition of the Coordinates with specified number of decimals.
boolean	equals(java.lang.Object o) Test equality of Coo.
static double[][]	eulerMatrix(double z, double theta, double zeta) Generate the rotation matrix from the Euler angles
double	getLat() Get the Latitude (Dec) in degrees.
double	getLon() Get the Longitude (RA) in degrees.
double[][]	localMatrix() Compute the rotation matrix associated to current position.
void	localMatrix(double[][] R) Compute the rotation matrix associated to current position.
static double[][]	localMatrix(double lon, double lat) Compute the rotation matrix that transforms a direction into the local frame.
double[][]	moveMatrix(Coo coo2) Compute the rotation matrix to move between 2 directions.
double	normalize() Normalisation of coordinates (set its norm to 1)
static double	normalize(double[] u) Normalisation of a vector (set its norm to 1)
int	parse(java.lang.String text, int offset) Interpret the string and convert to Coo.
boolean	parsing(Parsing acoo) Interpret the string and convert to Coo.
void	rotate_1(double[][] R) Rotate a coordinate (apply a rotation to the position) in reverse direction.
void	rotate(double[][] R) Rotate a coordinate (apply a rotation to the position).
static void	rotateVector_1(double[][] R, double[] v) Reversely rotate a vector.
static void	rotateVector(double[][] R, double[] v) Rotate a vector.
void	set() Sets the position to its default (unknown)
void	set(Coo coo) Set the position from an existing one.
void	set(double lon, double lat) Set a position from its longitude and latitude (RA/Dec).
void	set(double x, double y, double z) Set a position from its unit vectors.
void	set(java.lang.String text) Define a non-equatorial coordinate from its text (RA is in degrees)
static int	setDecimals(int nd) Set (and get) the number of decimals for the default edition of the cordinates.
static void	setUvec(double lon, double lat, double[] u) Compute the unit vector from angles in degrees.
double	sub(double[] du) Subtraction of a vector (subtravtion, then normalisation)
static double	sub(double[] u, double[] du) Subtraction of a vector (subtravtion, then normalisation)
java.lang.String	toString() Default Edition of the Coordinates, as 2 numbers expressing the angles in degrees.

Methods inherited from class java.lang.Object

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

Field Detail

x

public double x

Components of unit vector (direction cosines)

y

public double y

Components of unit vector (direction cosines)

z

public double z

Components of unit vector (direction cosines)

ed

public static Editing ed

The edition of Coordinates

decimals

public static int decimals

Number of decimals edited in the default toString method. Can be changed with the setDecimals() method.

Umatrix3

public static double[][] Umatrix3

The unit 3-D unit matrix .

Constructor Detail

Coo

public Coo()

The basic contructor: undefined position

Coo

public Coo(double lon,
           double lat)

Define a coordinate from its angles

Parameters:

lon - longitude angle in degrees

lat - latitude angle in degrees

Coo

public Coo(double x,
           double y,
           double z)

Define a coordinate from its direction cosines. (Note that (x,y,z) doesn't need to have a norm=1)

Parameters:

x - x item in unit vector (direction cosines)

y - y item in unit vector (direction cosines)

z - z item in unit vector (direction cosines)

Coo

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

Define a coordinate from a string

Parameters:

text - a position as a string

Throws:

java.text.ParseException - when the string is not interpretable

Method Detail

clone

public java.lang.Object clone()

Clone the Coo object

Overrides:

clone in class java.lang.Object

set

public void set()

Sets the position to its default (unknown)

set

public void set(Coo coo)

Set the position from an existing one. It is faster than the set methods from angles or vector components because there is no conversion.

Parameters:

coo - the coordinates

setUvec

public static final void setUvec(double lon,
                                 double lat,
                                 double[] u)

Compute the unit vector from angles in degrees.

Parameters:

lon - longitude in degrees

lat - latitude angle in degrees

u - resulting unit vector

set

public void set(double lon,
                double lat)

Set a position from its longitude and latitude (RA/Dec). Convert (lon,lat) into its direction cosines (x,y,z)

Parameters:

lon - longitude in degrees

lat - latitude angle in degrees

set

public void set(double x,
                double y,
                double z)

Set a position from its unit vectors. Revert conversion of (x,y,z) into (lon,lat).
(Note that (x,y,z) is assxumed to have a norm=1)

Parameters:

x - x item in unit vector (direction cosines)

y - y item in unit vector (direction cosines)

z - z item in unit vector (direction cosines)

parsing

public boolean parsing(Parsing acoo)

Interpret the string and convert to Coo. Called from set(...) and parse(...) methods

Parameters:

acoo - a text ready for parsing (may contain the hms or °'" characters)

Returns:

true if OK.

parse

public int parse(java.lang.String text,
                 int offset)

Interpret the string and convert to Coo.

Parameters:

text - a text containing 2 angles, in decimal or Sexagesimal (may contain the hms or °'" characters)

offset - where to start the analysis

Returns:

new position in text after interpretation.

set

public void set(java.lang.String text)
         throws java.text.ParseException

Define a non-equatorial coordinate from its text (RA is in degrees)

Parameters:

text - a text containing 2 angles, in decimal or Sexagesimal

Throws:

java.text.ParseException - when the string is not interpretable

getLon

public double getLon()

Get the Longitude (RA) in degrees.

Returns:

the longitude (RA) in degrees

getLat

public double getLat()

Get the Latitude (Dec) in degrees.

Returns:

the latitude (Dec) in degrees

copyAngles

public void copyAngles(double[] o)

Get the spherical angles (lon, lat) as a 2-vector

copyUvector

public void copyUvector(double[] u)

Get the unit vector (x, y, z) as a 3-vector

distance

public static final double distance(double lon1,
                                    double lat1,
                                    double lon2,
                                    double lat2)

Distance between 2 points on the sphere.

Parameters:

lon1 - longitude of first point in degrees

lat1 - latitude of first point in degrees

lon2 - longitude of second point in degrees

lat2 - latitude of second point in degrees

Returns:

distance in degrees in range [0, 180]

distance

public final double distance(Coo pos)

Distance between 2 points on the sphere.

Parameters:

pos - another position on the sphere

Returns:

distance in degrees in range [0, 180]

rotateVector

public static final void rotateVector(double[][] R,
                                      double[] v)

Rotate a vector. The vector v becomes R . v

Parameters:

R - [3][3] Rotation Matrix

v - Vector to rotate, may be of dimension 3 or 6.

rotateVector_1

public static final void rotateVector_1(double[][] R,
                                        double[] v)

Reversely rotate a vector. The vector v becomes R^-1 . v

Parameters:

R - [3][3] Rotation Matrix

v - Vector to rotate, may be of dimension 3 or 6.

rotate

public void rotate(double[][] R)

Rotate a coordinate (apply a rotation to the position).

Parameters:

R - [3][3] Rotation Matrix

rotate_1

public void rotate_1(double[][] R)

Rotate a coordinate (apply a rotation to the position) in reverse direction. The method is the inverse of rotate.

Parameters:

R - [3][3] Rotation Matrix

eulerMatrix

public static double[][] eulerMatrix(double z,
                                     double theta,
                                     double zeta)

Generate the rotation matrix from the Euler angles

Parameters:

z - Euler angle

theta - Euler angle

zeta - Euler angles

Returns:

R [3][3] the rotation matrix The rotation matrix is defined by:

    R =      R_z(-z)      ·        R_y(theta)     ·     R_z(-zeta)
             |cos.z -sin.z  0|   |cos.the  0 -sin.the|   |cos.zet -sin.zet 0|
           = |sin.z  cos.z  0| x |   0     1     0   | x |sin.zet  cos.zet 0|
             |   0      0   1|   |sin.the  0  cos.the|   |   0        0    1|
 

localMatrix

public static final double[][] localMatrix(double lon,
                                           double lat)

Compute the rotation matrix that transforms a direction into the local frame. The axises of the local frame are defined by:

• R[0] (first axis) = unit vector towards Zenith
• R[1] (second axis) = unit vector towards East
• R[2] (third axis) = unit vector towards North

  +-                             -+   +-                  -+
  | cosb.cosl   cosb.sinl    sinb |   |  x        y      z |
  |  -sinl        cosl        0   | = | (-y/r)   (x/r)   0 |
  |-sinb.cosl  -sinb.sinl    cosb |   |-z(x/r)  z(-y/r)  r |
  +-                             -+   +-                  -+
  

r = sqrt(x*x+y*y) ; if r==0,take (x/r)=1, (y/r)=0

Parameters:

lon - longitude of the center of local frame

lat - latitude of the center of local frame

Returns:

R[3][3] = Rotation Matrix [(x,y,z)_local = R * (x,y,z)_global]. With the result matrix, rotate(R) converts the position to (0,0).

localMatrix

public final void localMatrix(double[][] R)

Compute the rotation matrix associated to current position. Simple mathematics R[0][i] = I (x y z) R[1][i] = J (u v 0) R[2][i] = K (u v 0)

Parameters:

R - = Rotation Matrix[3][3] to transform the current position into (0,0)

localMatrix

public final double[][] localMatrix()

Compute the rotation matrix associated to current position.

Returns:

R[3][3] = Rotation Matrix to transform the current position into (0,0)

moveMatrix

public final double[][] moveMatrix(Coo coo2)

Compute the rotation matrix to move between 2 directions. This matrix is coo.localMatrix · t(this.localMatrix)

Parameters:

coo2 - target direction.

Returns:

R[3][3] = Rotation Matrix to transform the current position into the position given in argument

normalize

public static final double normalize(double[] u)

Normalisation of a vector (set its norm to 1)

Parameters:

u - 3- or 6-Vector to normalize

Returns:

the norm of the 3-D vector

normalize

public double normalize()

Normalisation of coordinates (set its norm to 1)

Returns:

the norm of the 3-D vector

add

public static final double add(double[] u,
                               double[] du)

Addition of a vector (addition, then normalisation)

Parameters:

u - 3- or 6-Vector to modify

du - 3-Vector to add

Returns:

the norm of the 3-D vector

sub

public static final double sub(double[] u,
                               double[] du)

Subtraction of a vector (subtravtion, then normalisation)

Parameters:

u - 3- or 6-Vector to modify

du - 3-Vector to subtract

Returns:

the norm of the 3-D vector

add

public final double add(double[] du)

Addition of a vector (addition, then normalisation)

Parameters:

du - 3-Vector to add

Returns:

the norm of the 3-D vector

sub

public final double sub(double[] du)

Subtraction of a vector (subtravtion, then normalisation)

Parameters:

du - 3-Vector to subtract

Returns:

the norm of the 3-D vector

equals

public boolean equals(java.lang.Object o)

Test equality of Coo.

Overrides:

equals in class java.lang.Object

Parameters:

o - Object to compare

Returns:

True if o is identical to Coo.

editCoo

public final java.lang.StringBuffer editCoo(java.lang.StringBuffer b,
                                            int nd)

Edition of the Coordinates with specified number of decimals.

Parameters:

b - the StringBuffer for edition

nd - the number of decimals in the edition of each coordinate. Possible to use a negative nd to minimize the length.

Returns:

the StringBuffer

edit

public java.lang.StringBuffer edit(java.lang.StringBuffer b,
                                   int nd)

Default Edition of the Coordinates, as 2 numbers expressing the angles in degrees.

Parameters:

b - the StringBuffer for edition

nd - the number of decimals in the edition of each coordinate. Possible to use a negative nd to minimize the length.

Returns:

the StringBuffer

setDecimals

public static int setDecimals(int nd)

Set (and get) the number of decimals for the default edition of the cordinates.

Parameters:

nd - the number of decimals in the edition of each coordinate. Possible to use a negative nd to minimize the length.

Returns:

the previous deifnition.

toString

public java.lang.String toString()

Default Edition of the Coordinates, as 2 numbers expressing the angles in degrees.

Overrides:

toString in class java.lang.Object

Returns:

The edited coordinates

dump

public void dump(java.lang.String title)

Dump the contents of a Coordinate

Parameters:

title - A title to precede the dump