healpix.core
Class Healpix

java.lang.Object
  healpix.core.Healpix

public final class Healpix
extends Object

Java version of some healpix routines from DSRI in java everthing must be in a class - no functions floating about. Original algorithms Eric Hivon and Krzysztof M. Gorski. Healpix.core.Healpixmap does this for a fixed nside This code written by William O'Mullane THIS IS 32 BIT - if you want 64 use HealpixIndex

Version:

$Id: Healpix.java,v 1.1.2.4 2010/02/22 14:55:50 healpix Exp $

Author:

womullan

ns_max

public static final int ns_max

The Constant ns_max.

See Also:

Constant Field Values

Healpix

public Healpix()

ang2pix_nest

public static final int ang2pix_nest(int nside,
                                     double theta,
                                     double phi)
                              throws Exception

renders the pixel number ipix (NESTED scheme) for a pixel which contains a point on a sphere at coordinates theta and phi, given the map resolution parametr nside the computation is made to the highest resolution available (nside=8192) and then degraded to that required (by integer division) this doesn't cost more, and it makes sure that the treatement of round-off will be consistent for every resolution

Parameters:

nside - resolution parameter

theta - angle (along meridian), in [0,Pi], theta=0 : north pole

phi - angle (along parallel), in [0,2*Pi] * @return pixel index nested

Throws:

Exception

pix2ang_nest

public static final AngularPosition pix2ang_nest(int nside,
                                                 int ipix)
                                          throws Exception

Convert from pix number to angle renders theta and phi coordinates of the nominal pixel center for the pixel number ipix (NESTED scheme) given the map resolution parameter nside

Parameters:

nside - resolution parameter

ipix - index in nest scheme

Returns:

angular position

Throws:

Exception

pix2ang_ring

public static final AngularPosition pix2ang_ring(int nside,
                                                 int ipix)
                                          throws Exception

Convert from pix number to angle renders theta and phi coordinates of the nominal pixel center for the pixel number ipix (RING scheme) given the map resolution parameter nside *

Parameters:

nside - resolution parameter

ipix - index in ring scheme

Returns:

angular position

Throws:

Exception

ang2pix_ring

public static final int ang2pix_ring(int nside,
                                     double theta,
                                     double phi)
                              throws Exception

renders the pixel number ipix (RING scheme) for a pixel which contains a point on a sphere at coordinates theta and phi, given the map resolution parametr nside the computation is made to the highest resolution available (nside=8192) and then degraded to that required (by integer division) this doesn't cost more, and it makes sure that the treatement of round-off will be consistent for every resolution

Parameters:

nside - resolution parameter

theta - angle (along meridian), in [0,Pi], theta=0 : north pole

phi - angle (along parallel), in [0,2*Pi]

Returns:

pixel index in ring scheme

Throws:

Exception

nest2ring

public static final int nest2ring(int nside,
                                  int ipnest)
                           throws Exception

performs conversion from NESTED to RING pixel number

Parameters:

nside - resolution parameter

ipnest - index in nested scheme

Returns:

index in ring scheme

Throws:

Exception

ring2nest

public static final int ring2nest(int nside,
                                  int ipring)
                           throws Exception

performs conversion from RING to NESTED pixel number

Parameters:

nside - resolution parameter

ipring - index pixel in ring scheme

Returns:

index in nest scheme

Throws:

Exception

pix2xy_nest

public static final Point pix2xy_nest(int nside,
                                      int ipix)
                               throws Exception

Convert from pix number to x,y inside a given face. 0,0 is the lower right corner of the face.

Parameters:

nside - resolution parameter

ipix - index pixel nested

Returns:

x,y Point

Throws:

Exception

xy2pix_nest

public static final int xy2pix_nest(int nside,
                                    int ix,
                                    int iy,
                                    int face)
                             throws Exception

Convert from a x,y in a given face to a pix number.

Parameters:

nside - resolution parameter

ix - x poisiton

iy - y position

face - face number

Returns:

index pixel nested

Throws:

Exception

xy2pix_nest

public static final int xy2pix_nest(int nside,
                                    Point p,
                                    int face)
                             throws Exception

Convert from a point in a given face to a pix number. Convenience method just unpacks the point to x and y and calls the other xy2pix_nest method.

Parameters:

nside - resolution parameter

p - x,y point object

face - face number

Returns:

index pixel nested

Throws:

Exception

xy2pix_nest

public static final int xy2pix_nest(int ix,
                                    int iy)
                             throws Exception

Convert from a x,y in a given face to a pix number in a face without offset.

Parameters:

ix - x position

iy - y position

Returns:

index pixel nested

Throws:

Exception

pix2xy_nest

public static final Point pix2xy_nest(int ipix)
                               throws Exception

Convert from pix number to x,y inside a given face. 0,0 is the lower right corner of the face.

Parameters:

ipix - index nested scheme

Returns:

x,y Point

Throws:

Exception

integration_limits_in_costh

public static final double[] integration_limits_in_costh(int n_side,
                                                         int i_th)

integration limits in cos(theta) for a given ring i_th, i_th > 0

Parameters:

n_side - resolution parameter

i_th - ith ring

Returns:

limits

pixel_boundaries

public static final double[] pixel_boundaries(int nside,
                                              double i_th,
                                              double i_phi,
                                              int i_zone,
                                              double cos_theta)

calculate the points of crossing for a given theta on the boundaries of the pixel - returns the left and right phi crossings

Parameters:

nside - resolution parameter

i_th - ith pixel

i_phi - phi angle

i_zone - ith zone (0,...,3), a quarter of sphere

cos_theta - theta cosinus

Returns:

the left and right phi crossings

ring

public static final int ring(int nside,
                             int ipix)
                      throws Exception

return ring number for given pix in ring scheme

Parameters:

nside - resolution parameter

ipix - index pixel in ring scheme

Returns:

ring number

Throws:

Exception

in_ring

public int[] in_ring(int nside,
                     int iz,
                     double phi0,
                     double dphi,
                     boolean nest)
              throws Exception

returns the list of pixels in RING or NESTED scheme (listir) with latitude in [phi0-dphi, phi0+dphi] on the ring ir (in {1,4*nside-1}) the pixel id-numbers are in {0,12*nside^2-1} the indexing is RING, unless NEST is set to true

Parameters:

nside - resolution parameter

iz - ring number

phi0 - phi angle

dphi - delta phi

nest - scheme flag: nest scheme if true, ring scheme otherwise

Returns:

list of pxiel indexes in ring

Throws:

Exception

query_disc

public int[] query_disc(int nside,
                        SpatialVector vector0,
                        double radius,
                        boolean nest,
                        boolean inclusive)
                 throws Exception

query_disc (Nside, Vector0, Radius, Listpix, Nlist[, Nest, Inclusive]). routine for pixel query in the RING or NESTED scheme. All pixels within an angular distance Radius of the center. Nside = resolution parameter (a power of 2); Vector0 = central point vector position (x,y,z in double precision); Radius = angular radius in RADIAN (in double precision); Listpix = list of pixel closer to the center (angular distance) than Radius; Nlist = number of pixels in the list; nest (OPT), :0 by default, the output list is in RING scheme; if set to 1, the output list is in NESTED scheme; inclusive (OPT) , :0 by default, only the pixels whose center; lie in the triangle are listed on output; if set to 1, all pixels overlapping the triangle are output; all pixel numbers are in {0, 12*Nside*Nside - 1} NB : the dimension of the listpix array is fixed in the ing; routine and should be large enough for the specific configuration. lower level public void s ed by getdisc_ring : (you don't need to know them); ring_num (nside, ir); in_ring(nside, iz, phi0, dphi, listir, nir, nest=nest);

Parameters:

nside - resolution parameter

vector0 - SpatialVector poitnig to disc

radius - disc radius

nest - scheme nest if true

inclusive - include disc flag

Returns:

list of index pixel contained in disc

Throws:

Exception

ring_num

public int ring_num(int nside,
                    double z)

returns the ring number in {1, 4*nside-1} from the z coordinate.

Parameters:

nside - resoultion parameter

z - z coordinate

Returns:

ring number