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// Copyright 2021 - Unistra/CNRS
// The MOC API project is distributed under the terms
// of the GNU General Public License version 3.
//
//This file is part of MOC API java project.
//
// MOC API java project is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, version 3 of the License.
//
// MOC API java project 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 General Public License for more details.
//
// The GNU General Public License is available in COPYING file
// along with MOC API java project.
//
package cds.moc;
import static cds.healpix.Healpix.nHash;
import cds.healpix.FlatHashIterator;
import cds.healpix.HealpixNestedBMOC;
import cds.healpix.HealpixNestedFixedRadiusConeComputer;
/** HEALPix CDS wrapper
* Encapsulate the usage of the HEALpix lib
*
* The HEALPix ordering is always NESTED
*
* @author Pierre Fernique [CDS]
* @version 1.3 May 2014 - NPIX => UNIQ fits keyword
* @version 1.2 Jan 2012 - Thread safe implementation
* @version 1.1 Oct 2011 - direct HealpixBase use
* @version 1.0 May 2011
*/
public final class Healpix implements HealpixImpl {
/** Provide the HEALPix number associated to a coord, for a given order
* @param order HEALPix order [0..MAXORDER]
* @param lon longitude (expressed in the Healpix frame)
* @param lat latitude (expressed in the Healpix frame)
* @return HEALPix number
* @throws Exception
*/
public long ang2pix(int order,double lon, double lat) throws Exception {
return cds.healpix.Healpix.getNestedFast(order).hash(Math.toRadians(lon), Math.toRadians(lat));
}
/** Provide the spherical coord associated to an HEALPix number, for a given order
* @param order HEALPix order [0..MAXORDER]
* @param npix HEALPix number
* @return coord (lon,lat) (expressed in the Healpix frame)
* @throws Exception
*/
public double [] pix2ang(int order,long npix) throws Exception {
final double[] lonlat = cds.healpix.Healpix.getNestedFast(order).center(npix);
lonlat[0] = Math.toDegrees(lonlat[0]);
lonlat[1] = Math.toDegrees(lonlat[1]);
return lonlat;
}
/** Provide the list of HEALPix numbers fully covering a circle (for a specified order)
* @param order Healpix order
* @param lon center longitude (expressed in the Healpix frame)
* @param lat center latitude (expressed in the Healpix frame)
* @param radius circle radius (in degrees)
* @return
* @throws Exception
*/
public long [] queryDisc(int order, double lon, double lat, double radius) throws Exception {
lon = Math.toRadians(lon);
lat = Math.toRadians(lat);
radius = Math.toRadians(radius);
// Exact
// HealpixNestedFixedRadiusConeComputer cc = cds.healpix.Healpix.getNested(order).newConeComputer(coneRadiusRad)
// Approx
HealpixNestedFixedRadiusConeComputer cc = cds.healpix.Healpix.getNested(order).newConeComputerApprox(radius);
HealpixNestedBMOC bmoc = cc.overlappingCells(lon, lat);
long[] cells = new long[(int) bmoc.computeDeepSize()];
FlatHashIterator it = bmoc.flatHashIterator();
for(int i = 0; it.hasNext(); i++) {
cells[i] = it.next();
}
return cells;
}
/*********************** Healpix Utilities ***************************************************/
static public final double SKYAREA = 4.*Math.PI*Math.toDegrees(1.0)*Math.toDegrees(1.0);
static public final long pow2(long order){ return 1L<<order;}
/** Pixel area (in square degrees) for a given HEALPix order */
static public double getPixelArea(int order) {
if( order < 0 ) return SKYAREA;
return SKYAREA/nHash(order);
}
}
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