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# Class FITSWCS.projections.SINProjection

    java.lang.Object
       |
       +----FITSWCS.Projection
               |
               +----FITSWCS.projections.SINProjection

public class SINProjection
extends Projection

This class provides support for the orthographic/synthesis projection (SIN) used by the FITS "World Coordinate System" (WCS) convention.

The FITSWCS package was translated from the WCSLIB C library. This original library was written in support for coordinate systems used by astronomical data stored in FITS format. For more information on these coordinate systems, refer to the paper by Greisen and Calabretta at:

> ftp://fits.cv.nrao.edu/fits/documents/wcs/wcs.all.ps.Z

Nomenclature

In WCSLIB the "forward" direction is from (lng,lat) celestial coordinates to (x,y) coordinates in the plane of projection. This accords with the notion that spherical projections are a projection of the sphere onto a plane, the "reverse" direction is therefore that of deprojection from plane to sphere.

Unfortunately, this is opposite to what is generally understood to be the forward direction for FITS, namely that of transforming pixel coordinates to world coordinates. However, the ordering of function argument lists should make it clear what is intended.

Accuracy

Closure to a precision of at least 1.0-10 degree of longitude and latitude has been verified for typical projection parameters on the 1 degree grid of native longitude and latitude (to within 5 degrees of any latitude where the projection may diverge). Notwithstanding this, absolutely no claim is made for the accuracy or reliability of these routines. They are supplied as is, with no warranty of fitness for any purpose.

COPYRIGHT NOTICE

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details.

You should have received a copy of the GNU Library General Public License along with this library; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

Correspondence concerning WCSLIB may be directed to:

         Internet email: mcalabre@atnf.csiro.au
         Postal address: Dr. Mark Calabretta,
                         Australia Telescope National Facility,
                         P.O. Box 76,
                         Epping, NSW, 2121,
                         AUSTRALIA

Correspondence concerning the Java implementation may be directed to Raymond L. Plante (rplante@ncsa.uiuc.edu).

##

tol

##

SINProjection()
  Create an SINProjection object (with no obliqueness)
SINProjection(double, double)
  Create an SINProjection object with a given obliqueness
SINProjection(double, double, double)
  Create an SINProjection object
SINProjection(double, double[])
  Create an SINProjection object
SINProjection(double[])
  Create an SINProjection object

##

fwd(double, double)
  Compute (x,y) coordinates in the plane of projection from native spherical coordinates (phi,theta).
fwd(double[])
  same as fwd(phitheta[0], phitheta[1])
rev(double, double)
  Compute native spherical coordinates (phi,theta) from the (x,y) coordinates in the plane of projection.
setProjParm(double[])
  set the projection parameters
setR0(double)
  set the sphere radius

##

tol

      protected final static double tol

##

SINProjection

      public SINProjection()

  Create an SINProjection object (with no obliqueness)

SINProjection

      public SINProjection(double opa,
                           double opb)

  Create an SINProjection object with a given obliqueness
  Parameters:
    opa - obliqueness parameters alpha
    opb - obliqueness parameters beta
  Throws: BadProjectionParameterException
    if p[1] = -1;

SINProjection

      public SINProjection(double r0,
                           double opa,
                           double opb)

  Create an SINProjection object
  Parameters:
    r0 - sphere radius
    opa - obliqueness parameters alpha
    opb - obliqueness parameters beta
  Throws: BadProjectionParameterException
    if p[1] = -1;

SINProjection

      public SINProjection(double r0,
                           double p[]) throws ArrayIndexOutOfBoundsException

  Create an SINProjection object
  Parameters:
    r0 - sphere radius
    p - projection parameters specifying the obliqueness, where p[1] is the alpha parameter and p[2] is the beta parameter
  Throws: ArrayIndexOutOfBoundsException
    if p.length < 3;
  Throws: BadProjectionParameterException
    if p[1] = -1;

SINProjection

      public SINProjection(double p[]) throws ArrayIndexOutOfBoundsException

  Create an SINProjection object
  Parameters:
    p - projection parameters, where p[1] is the SIN distance parameter, mu in units of 180/PI.
  Throws: ArrayIndexOutOfBoundsException
    if p.length < 2;

##

fwd

      public double[] fwd(double phi,
                          double theta)

  Compute (x,y) coordinates in the plane of projection from native spherical coordinates (phi,theta).
  Returns:
    double[] a two-element array containing x,y
  Overrides:
    fwd in class Projection

fwd

      public double[] fwd(double phitheta[])

  same as fwd(phitheta[0], phitheta[1])
  Overrides:
    fwd in class Projection

rev

      public double[] rev(double x,
                          double y) throws PixelBeyondProjectionException

  Compute native spherical coordinates (phi,theta) from the (x,y) coordinates in the plane of projection.
  Returns:
    double[] a two-element array containing phi,theta
  Overrides:
    rev in class Projection

setR0

      public void setR0(double r0)

  set the sphere radius
  Overrides:
    setR0 in class Projection

setProjParm

      public void setProjParm(double p[]) throws ArrayIndexOutOfBoundsException

  set the projection parameters
  Parameters:
    p - array of projection parameters; if p is null, no update is to be made.
  Overrides:
    setProjParm in class Projection

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