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java.lang.Object | +----FITSWCS.Projection
The FITSWCS package was translated from the WCSLIB C library (V2.3). 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.ZNomenclature
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.
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, AUSTRALIACorrespondence concerning the Java implementation may be directed to Raymond L. Plante (rplante@ncsa.uiuc.edu).
protected double r0
protected double p[]
protected double w[]
protected int n
public final static double PI
public final static double D2R
public final static double R2D
public final static double SQRT2
public final static double SQRT2INV
public Projection()
public abstract double[] fwd(double phi, double theta) throws PixelBeyondProjectionException
The values of phi and theta (the native longitude and latitude) normally lie in the range [-180,180] for phi, and [-90,90] for theta. However, all forward projections will accept any value of phi and will not normalize it.
Although many of the forward projections will accept values of theta outside the range [-90,90] such latitudes are not meaningful and should normally be marked as an error. However, in the interests of efficiency, the forward projection routines do not check for this, although they do check for any invalid values of theta within the range [-90,90].
public double[] fwd(double phitheta[]) throws PixelBeyondProjectionException
public abstract double[] rev(double x, double y) throws PixelBeyondProjectionException
Error checking on the projected coordinates (x,y) is limited to that required to ascertain whether a solution exists. Where a solution does exist no check is made that the value of phi and theta obtained lie within the ranges [-180,180] for phi, and [-90,90] for theta.
public double[] rev(double xy[]) throws PixelBeyondProjectionException
public double getR0()
public abstract void setR0(double r0)
public abstract void setProjParm(double p[]) throws ArrayIndexOutOfBoundsException, BadProjectionParameterException
public double[] getProjParm()
public final static Projection getProjection(String pcode, double projparm[]) throws ArrayIndexOutOfBoundsException, BadProjectionParameterException, UnsupportedProjectionException
public final static int projectionType(String name)
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