skyview.geometry

Class WCS

java.lang.Object

skyview.geometry.Transformer

skyview.geometry.Converter

skyview.geometry.WCS

All Implemented Interfaces:

java.io.Serializable, Component

public class WCS
extends Converter

A World Coordinate System defines a translation between celestial and pixel coordinates. Note that in many cases FITS keywords describe the transformations in the other direction (from pixel to celestial) but we follow the convention that forward transformations are from celestial to pixel. Given a WCS object, wcs, the pixel-celestial coordinates trasnformation is simply wcs.inverse();

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
WCS(CoordinateSystem csys, Projection proj, Scaler scale) Create a simple WCS given a scaler, CoordinateSystem and Projection.
WCS(nom.tam.fits.Header h) Create the WCS using the definition given in the FITS header.
WCS(nom.tam.fits.Header h, int lonAxis, int latAxis) Let the user say which axes to use

Method Summary

Modifier and Type	Method and Description
WCS	addScaler(Scaler shift) Return a new WCS from the existing WCS where we add a scale.
WCS	approximate(double[] pix) Approximate a WCS (which presumably includes a Distorter) with a standard, locally correct, WCS.
void	copyToHeader(nom.tam.fits.Header h)
CoordinateSystem	getCoordinateSystem() Get the CoordinateSystem used in the WCS
Distorter	getDistorter() Get the plane distorter used in the projection (or null)
int[]	getHeaderNaxis()
Projection	getProjection() Get the projection used in the WCS
double	getScale() Get the nominal scale of the WCS.
Scaler	getScaler() Get the linear scaler used in the projection
void	setHeaderNaxis(int[] newAxes)
static void	setPreferDSS(boolean flag)
boolean	standardWCS()
void	updateHeader(nom.tam.fits.Header h, Scaler s, double[] crval, java.lang.String projString, java.lang.String coordString) Write FITS WCS keywords given key values.

Methods inherited from class skyview.geometry.Converter

add, check, debug, getDescription, getInputDimension, getName, getOutputDimension, inverse, isInverse, printElements, transform

Methods inherited from class skyview.geometry.Transformer

transform, transform

Methods inherited from class java.lang.Object

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

Constructor Detail

WCS

public WCS(CoordinateSystem csys,
           Projection proj,
           Scaler scale)
    throws TransformationException

Create a simple WCS given a scaler, CoordinateSystem and Projection.

Throws:

TransformationException

WCS

public WCS(nom.tam.fits.Header h)
    throws TransformationException

Create the WCS using the definition given in the FITS header.

Throws:

TransformationException

WCS

public WCS(nom.tam.fits.Header h,
           int lonAxis,
           int latAxis)
    throws TransformationException

Let the user say which axes to use

Throws:

TransformationException

Method Detail

addScaler

public WCS addScaler(Scaler shift)
              throws TransformationException

Return a new WCS from the existing WCS where we add a scale. This allows us to return a WCS for a subset of an image easily.

Throws:

TransformationException

setPreferDSS

public static void setPreferDSS(boolean flag)

getCoordinateSystem

public CoordinateSystem getCoordinateSystem()

Get the CoordinateSystem used in the WCS

getProjection

public Projection getProjection()

Get the projection used in the WCS

getScaler

public Scaler getScaler()

Get the linear scaler used in the projection

getDistorter

public Distorter getDistorter()

Get the plane distorter used in the projection (or null)

standardWCS

public boolean standardWCS()

getHeaderNaxis

public int[] getHeaderNaxis()

setHeaderNaxis

public void setHeaderNaxis(int[] newAxes)

getScale

public double getScale()

Get the nominal scale of the WCS.

updateHeader

public void updateHeader(nom.tam.fits.Header h,
                         Scaler s,
                         double[] crval,
                         java.lang.String projString,
                         java.lang.String coordString)
                  throws java.lang.Exception

Write FITS WCS keywords given key values. Only relatively simple WCSs are handled here. We assume we are dealing with axes 1 and 2.

Parameters:

h - The header to be updated.

s - A Scaler giving the transformation between standard projection coordinates and pixel/device coordinates.

projString - A three character string giving the projection used. Supported projections are: "Tan", "Sin", "Ait", "Car", "Zea".

coordString - A string giving the coordinate system used. The first character gives the general frame. For most frames the remainder of the string gives the equinox o the coordinate system. E.g., J2000, B1950, Galactic, "E2000", "H2020.10375".

Throws:

java.lang.Exception

copyToHeader

public void copyToHeader(nom.tam.fits.Header h)
                  throws nom.tam.fits.HeaderCardException

Throws:

nom.tam.fits.HeaderCardException

approximate

public WCS approximate(double[] pix)
                throws TransformationException

Approximate a WCS (which presumably includes a Distorter) with a standard, locally correct, WCS.

Parameters:

pix - The pixel location we want to approximate around.

Returns:

A more standard WCS with the distortion removed (locally).

Throws:

TransformationException