jview
Class DssTransformation

java.lang.Object
  jview.DssTransformation

All Implemented Interfaces:

CoordinateTransforming, SkyTransforming

public class DssTransformation
extends Object
implements CoordinateTransforming, SkyTransforming

This transformation is used with DSS fits images retreived from the web. It uses various fits-keyword in the transferred file to convert from pixel coordinates to ra/dec and vice versa. The code is based on Doug Mink's dsspos.c code, which is distributed under GNU Lesser GPL. Download the original code from SAOImage.

Field Summary

private VectorG	amdx Plate solution x coeffiecients.
static String	AMDX Plate solution x coefficients, add 1-?.
private VectorG	amdy Plate solution y coeffiecients.
static String	AMDY Plate solution x coefficients, add 1-?.
private Vector2D	center The center of the DSS plate in ra/deg, both degrees.
static String	CNPIX1 Fits header keyword name.
static String	CNPIX2 Fits header keyword name.
static String	NAXIS1 Fits header keyword name.
static String	NAXIS2 Fits header keyword name.
private static double	OFFPLATE For reverse transform (to normalized pixel), a small number.
private VectorG	orientation Orientation coefficients, only index 2 and 5 used.
private Point2D	pixoff The position of the upper-left corner in normalized(!) pixel.
private Vector2D	pixsize The pixel size in microns of normalized(!) pixel.
private VectorDifferentiable	plate We use vector functions for evaluation of plate coordinates.
static String	PLTDECD Fits header keyword name.
static String	PLTDECM Fits header keyword name.
static String	PLTDECS Fits header keyword name.
static String	PLTDECSN Fits header keyword name.
static String	PLTRAH Fits header keyword name.
static String	PLTRAM Fits header keyword name.
static String	PLTRAS Fits header keyword name.
static String	PLTSCALE Fits header keyword name.
static String	PPO Orientation coefficients, add 1-6.
private double	scale The plate scale, used for inversion.
static String	XPIXELSZ Fits header keyword name.
static String	YPIXELSZ Fits header keyword name.

Constructor Summary

protected

DssTransformation(Vector2D radec, Point2D plateoff, double arcsec, Vector2D micron, VectorG rotmatrix, VectorG platexsolution, VectorG plateysolution) Constructs a DssTransform with all neccessary parameters.

Method Summary

static DssTransformation	parseFromDssHeader(nom.tam.fits.Header head) Factory method to generate DSS-transformations from a FITS-header.
Point2D	toNormalizedSpace(VectorG radec) Converts ra/dec into normalized coordinates.
VectorG	toUserSpace(Point2D norm) Converts normalized coordinates into user space, i.e.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

NAXIS1

public static final String NAXIS1

Fits header keyword name.

See Also:

Constant Field Values

NAXIS2

public static final String NAXIS2

Fits header keyword name.

See Also:

Constant Field Values

PLTRAH

public static final String PLTRAH

Fits header keyword name.

See Also:

Constant Field Values

PLTRAM

public static final String PLTRAM

Fits header keyword name.

See Also:

Constant Field Values

PLTRAS

public static final String PLTRAS

Fits header keyword name.

See Also:

Constant Field Values

PLTDECSN

public static final String PLTDECSN

Fits header keyword name.

See Also:

Constant Field Values

PLTDECD

public static final String PLTDECD

Fits header keyword name.

See Also:

Constant Field Values

PLTDECM

public static final String PLTDECM

Fits header keyword name.

See Also:

Constant Field Values

PLTDECS

public static final String PLTDECS

Fits header keyword name.

See Also:

Constant Field Values

PLTSCALE

public static final String PLTSCALE

Fits header keyword name.

See Also:

Constant Field Values

CNPIX1

public static final String CNPIX1

Fits header keyword name.

See Also:

Constant Field Values

CNPIX2

public static final String CNPIX2

Fits header keyword name.

See Also:

Constant Field Values

XPIXELSZ

public static final String XPIXELSZ

Fits header keyword name.

See Also:

Constant Field Values

YPIXELSZ

public static final String YPIXELSZ

Fits header keyword name.

See Also:

Constant Field Values

PPO

public static final String PPO

Orientation coefficients, add 1-6. Need at least 3 and 6.

See Also:

Constant Field Values

AMDX

public static final String AMDX

Plate solution x coefficients, add 1-?. Need at least 1 to 13.

See Also:

Constant Field Values

AMDY

public static final String AMDY

Plate solution x coefficients, add 1-?. Need at least 1 to 13.

See Also:

Constant Field Values

OFFPLATE

private static final double OFFPLATE

For reverse transform (to normalized pixel), a small number.

See Also:

Constant Field Values

center

private Vector2D center

The center of the DSS plate in ra/deg, both degrees.

pixoff

private Point2D pixoff

The position of the upper-left corner in normalized(!) pixel.

scale

private double scale

The plate scale, used for inversion.

pixsize

private Vector2D pixsize

The pixel size in microns of normalized(!) pixel.

orientation

private VectorG orientation

Orientation coefficients, only index 2 and 5 used. Must be N6.

amdx

private VectorG amdx

Plate solution x coeffiecients. Must be at least N14.

amdy

private VectorG amdy

Plate solution y coeffiecients. Must be at least N14.

plate

private VectorDifferentiable plate

We use vector functions for evaluation of plate coordinates.

Constructor Detail

DssTransformation

protected DssTransformation(Vector2D radec,
                            Point2D plateoff,
                            double arcsec,
                            Vector2D micron,
                            VectorG rotmatrix,
                            VectorG platexsolution,
                            VectorG plateysolution)

Constructs a DssTransform with all neccessary parameters. The parameter can be parsed out of DSS-Fits Headers using the factory method parseFromDssHeader(nom.tam.fits.Header).

Warning: Plate offset and pixel size in microns given in the FITS header must be translated to represent normalized pixel.

See Also:

parseFromDssHeader(nom.tam.fits.Header)

Method Detail

toNormalizedSpace

public Point2D toNormalizedSpace(VectorG radec)

Converts ra/dec into normalized coordinates. This involves newton approximation and is thus much slower than the 'forward' transformation toUserSpace(java.awt.geom.Point2D), which is good, as toUserSpace(java.awt.geom.Point2D) is often coupled with a mouse-motion listener.

Specified by:

toNormalizedSpace in interface CoordinateTransforming

Parameters:

radec - A vector of user coordinates.

Returns:

A point in normalized screen coordinate, with 0≤x,y≤1

See Also:

parseFromDssHeader(nom.tam.fits.Header)

toUserSpace

public VectorG toUserSpace(Point2D norm)

Converts normalized coordinates into user space, i.e. into ra/dec in degrees. Note that fits-header information works on true pixel, but we work on normalized pixels.

Specified by:

toUserSpace in interface CoordinateTransforming

Parameters:

norm - A pixel in normalized coordinates.

Returns:

A vector in user space, never null

See Also:

parseFromDssHeader(nom.tam.fits.Header)

parseFromDssHeader

public static final DssTransformation parseFromDssHeader(nom.tam.fits.Header head)
                                                  throws nom.tam.fits.BadHeaderException

Factory method to generate DSS-transformations from a FITS-header. The fits header is scanned for the necessary keywords for converting pixels to ra/dec and vice versae. The name of these keys plus example values are:

       NAXIS1  =                 1782 /Length X axis
       NAXIS2  =                 1786 /Length Y axis
       PLTRAH  =                    9 /Plate center RA
       PLTRAM  =                   22 /
       PLTRAS  =  3.9569489333335E+01 /
       PLTDECSN= '+                 ' /Plate center Dec
       PLTDECD =                    9 /
       PLTDECM =                   49 /
       PLTDECS =  4.0900600000001E+01 /
       PLTSCALE=  6.7199996948242E+01 /Plate Scale arcsec per mm
       CNPIX1  =                 3674 /X corner  (pixels)
       CNPIX2  =                13427 /Y corner
       XPIXELSZ=  1.5029459953308E+01 /X pixel size microns
       YPIXELSZ=  1.5000000000000E+01 /Y pixel size microns
       PPO1    = -3.0694170000000E+06 /Orientation Coefficients
       PPO2    =  0.0000000000000E+00 /
       PPO3    =  1.7750000000000E+05 /
       PPO4    =  0.0000000000000E+00 /
       PPO5    =  3.0694170000000E+06 /
       PPO6    =  1.7750000000000E+05 /
       AMDX1   =  6.7129457419911E+01 /Plate solution x coefficients
       AMDX2   =  1.3626646187870E-01 /
       AMDX3   = -2.9208496144965E+02 /
       AMDX4   = -2.9899239919615E-05 /
       AMDX5   =  2.5043127769380E-05 /
       AMDX6   = -5.7373181429586E-06 /
       AMDX7   =  0.0000000000000E+00 /
       AMDX8   =  2.2933676519874E-06 /
       AMDX9   = -4.0751949082659E-09 /
       AMDX10  =  2.3672449369580E-06 /
       AMDX11  = -4.7291435999810E-08 /
       AMDX12  =  0.0000000000000E+00 /
       AMDX13  =  0.0000000000000E+00 /
       AMDX14  =  0.0000000000000E+00 /
       AMDX15  =  0.0000000000000E+00 /
       AMDX16  =  0.0000000000000E+00 /
       AMDX17  =  0.0000000000000E+00 /
       AMDX18  =  0.0000000000000E+00 /
       AMDX19  =  0.0000000000000E+00 /
       AMDX20  =  0.0000000000000E+00 /
       AMDY1   =  6.7133343203278E+01 /Plate solution y coefficients
       AMDY2   = -1.3340634210135E-01 /
       AMDY3   =  3.1610776589125E+02 /
       AMDY4   =  2.8815934297932E-05 /
       AMDY5   = -1.8079494715991E-05 /
       AMDY6   =  1.6010028102203E-05 /
       AMDY7   =  0.0000000000000E+00 /
       AMDY8   =  2.3353722449029E-06 /
       AMDY9   = -2.5704411915230E-08 /
       AMDY10  =  2.3192988724761E-06 /
       AMDY11  = -2.5321357027618E-11 /
       AMDY12  =  0.0000000000000E+00 /
       AMDY13  =  0.0000000000000E+00 /
       AMDY14  =  0.0000000000000E+00 /
       AMDY15  =  0.0000000000000E+00 /
       AMDY16  =  0.0000000000000E+00 /
       AMDY17  =  0.0000000000000E+00 /
       AMDY18  =  0.0000000000000E+00 /
       AMDY19  =  0.0000000000000E+00 /
       AMDY20  =  0.0000000000000E+00 /
       

IMPORTANT INFORMATION:
To transform to normalized pixels and not to plate pixels, the information gather from the fits header is changed for the offset (CNPIX1, CNPIX2) to represent an offset in normalized space by

       offset_x,y=(CNPIX_1,2+0.5)/NAXIS_1,2
       

as well as the pixel size in micron (XPIXELSZ, YPIXELSZ) is changed to the normalized pixel size in microns:

       pixsize_x,y=(X,Y_PIXELSZ)*NAXIS_1,2
       

As a further detail, the plate center is recorded in degrees, not in radians as in the original SAO image code.

Throws:

nom.tam.fits.BadHeaderException - If not enough information is provided in the fits header to initialize the transformation.