Package healpix.essentials

Class HealpixBase

java.lang.Object
healpix.essentials.HealpixTables
healpix.essentials.HealpixBase
All Implemented Interfaces:
Serializable
Direct Known Subclasses:
HealpixMapDouble, HealpixMapFloat, HealpixProc
public class HealpixBase extends HealpixTables
Basic opersations related to the HEALPix pixelisation. This class is conceptually very similar the the Healpix_Base class of Healpix_cxx. It supports the NESTED scheme for nside parameters which are powers of 2, and the RING scheme for arbitrary positive nside parameters. The maximum supported nside parameter is 2^29.
Author:
Martin Reinecke
See Also:
Copyright:
2011, 2012 Max-Planck-Society

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    protected final class 
    HealpixBase.Xyf
     

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected double
    fact1
     
    protected double
    fact2
     
    protected long
    ncap
     
    protected long
    nl2
     
    protected long
    nl3
     
    protected long
    nl4
     
    protected long
    npface
     
    protected long
    npix
     
    static final long
    ns_max
    Maximum Nside parameter; equivalent to 2^order_max.
    protected long
    nside
    The Nside parameter.
    protected int
    order
    The order of the map; -1 when nside is not a power of 2.
    static final int
    order_max
    Maximum order parameter
    protected Scheme
    scheme
    The ordering scheme.

    Fields inherited from class healpix.essentials.HealpixTables

    ctab, facearray, jpll, jrll, swap_cycle, swaparray, utab, xoffset, yoffset

  • Constructor Summary

    Constructors
    Constructor
    Description
    HealpixBase()
    Initializes the object to Nside=1 and scheme=NESTED.
    HealpixBase(long nside_in, Scheme scheme_in)
    Initializes the object to a user-supplied Nside and ordering scheme.

  • Method Summary

    Modifier and Type
    Method
    Description
    long
    ang2pix(Pointing ptg)
    Returns the pixel which contains the supplied Pointing.
    Vec3[]
    boundaries(long pix, int step)
    Returns a set of points along the boundary of the given pixel.
    long
    getNpix()
    Returns the total number of pixels in the pixelisation.
    int
    getNside()
    Returns the current Nside parameter.
    int
    getOrder()
    Returns the current order parameter.
    Scheme
    getScheme()
    Returns the current ordering scheme.
    protected long
    loc2pix(healpix.essentials.Hploc loc)
     
    double
    maxPixrad()
    Returns the maximum angular distance between a pixel center and its corners.
    long[]
    neighbours(long ipix)
    Returns the neighboring pixels of ipix.
    long
    nest2ring(long ipnest)
    Returns ring pixel number for the supplied nested pixel number.
    static long
    npix2Nside(long npix)
    Calculates the Nside parameter from the number of pixels.
    static long
    nside2Npix(long nside)
    Calculates the number of pixels from the Nside parameter.
    static int
    nside2order(long nside)
    Calculates the map order from its Nside parameter.
    static long
    order2Npix(int order)
    Calculates the number of pixels from the order parameter.
    Pointing
    pix2ang(long pix)
    Returns the Pointing corresponding to the center of the supplied pixel.
    protected healpix.essentials.Hploc
    pix2loc(long pix)
     
    long
    pix2ring(long pix)
    Compute ring index from pixel number.
    Vec3
    pix2vec(long pix)
    Returns the normalized 3-vector corresponding to the center of the supplied pixel.
    protected HealpixBase.Xyf
    pix2xyf(long pix)
     
    Zphi
    pix2zphi(long pix)
    Returns the Zphi corresponding to the center of the supplied pixel.
    RangeSet
    queryDisc(Pointing ptg, double radius)
    Returns a range set of pixels whose centers lie within a given disk.
    RangeSet
    queryDiscInclusive(Pointing ptg, double radius, int fact)
    Returns a range set of pixels which overlap with a given disk.
    RangeSet
    queryPolygon(Pointing[] vertex)
    Returns a range set of pixels whose centers lie within the convex polygon defined by the vertex array.
    RangeSet
    queryPolygonInclusive(Pointing[] vertex, int fact)
    Returns a range set of pixels that overlap with the convex polygon defined by the vertex array.
    RangeSet
    queryStrip(double theta1, double theta2, boolean inclusive)
    Returns a range set of pixels whose centers lie within a given latitude range (if inclusive==false), or which overlap with this range (if inclusive==true).
    long
    ring2nest(long ipring)
    Returns nested pixel number for the supplied ring pixel number.
    double
    ring2theta(long ring)
    Returns the colatitude for the requested ring.
    protected HealpixBase.Xyf
    ring2xyf(long pix)
     
    double
    ring2z(long ring)
    Returns the z-coordinate (equivalent to the cosine of the colatitude) for the requested ring.
    void
    setNside(long nside_in)
    Adjusts the object to nside_in.
    void
    setNsideAndScheme(long nside_in, Scheme scheme_in)
    Adjusts the object to nside_in and scheme_in.
    void
    setScheme(Scheme scheme_in)
    Adjusts the object to scheme.
    long
    vec2pix(Vec3 vec)
    Returns the pixel which contains the supplied Vec3.
    protected long
    xyf2pix(int ix, int iy, int face_num)
     
    protected long
    xyf2pix(HealpixBase.Xyf xyf)
     
    long
    zphi2pix(Zphi zphi)
    Returns the pixel which contains the supplied Zphi.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • order_max

      public static final int order_max
      Maximum order parameter
      See Also:

    • ns_max

      public static final long ns_max
      Maximum Nside parameter; equivalent to 2^order_max.
      See Also:

    • order

      protected int order
      The order of the map; -1 when nside is not a power of 2.

    • nside

      protected long nside
      The Nside parameter.

    • nl2

      protected long nl2

    • nl3

      protected long nl3

    • nl4

      protected long nl4

    • npface

      protected long npface

    • npix

      protected long npix

    • ncap

      protected long ncap

    • fact1

      protected double fact1

    • fact2

      protected double fact2

    • scheme

      protected Scheme scheme
      The ordering scheme.

  • Constructor Details

    • HealpixBase

      public HealpixBase()
      Initializes the object to Nside=1 and scheme=NESTED.

    • HealpixBase

      public HealpixBase(long nside_in, Scheme scheme_in) throws Exception
      Initializes the object to a user-supplied Nside and ordering scheme.
      Parameters:
      nside_in - the Nside parameter
      scheme_in - the ordering scheme
      Throws:
      Exception

  • Method Details

    • ring2xyf

      protected HealpixBase.Xyf ring2xyf(long pix)

    • pix2xyf

      protected HealpixBase.Xyf pix2xyf(long pix)

    • xyf2pix

      protected long xyf2pix(int ix, int iy, int face_num)

    • xyf2pix

      protected long xyf2pix(HealpixBase.Xyf xyf)

    • nside2order

      public static int nside2order(long nside) throws Exception
      Calculates the map order from its Nside parameter.
      Parameters:
      nside - the Nside parameter
      Returns:
      the map order corresponding to nside; -1 if nside is not a power of 2.
      Throws:
      Exception

    • npix2Nside

      public static long npix2Nside(long npix) throws Exception
      Calculates the Nside parameter from the number of pixels.
      Parameters:
      npix - the number of pixels
      Returns:
      the computed Nside parameter
      Throws:
      Exception

    • nside2Npix

      public static long nside2Npix(long nside) throws Exception
      Calculates the number of pixels from the Nside parameter.
      Parameters:
      nside - the Nside parameter
      Returns:
      the computed number of pixels
      Throws:
      Exception

    • order2Npix

      public static long order2Npix(int order) throws Exception
      Calculates the number of pixels from the order parameter.
      Parameters:
      order - the order parameter
      Returns:
      the computed number of pixels
      Throws:
      Exception

    • setNside

      public void setNside(long nside_in) throws Exception
      Adjusts the object to nside_in.
      Parameters:
      nside_in - the new Nside parameter
      Throws:
      Exception

    • setNsideAndScheme

      public void setNsideAndScheme(long nside_in, Scheme scheme_in) throws Exception
      Adjusts the object to nside_in and scheme_in.
      Parameters:
      nside_in - the new Nside parameter
      scheme_in - the new ordering scheme
      Throws:
      Exception

    • getScheme

      public Scheme getScheme()
      Returns the current ordering scheme.
      Returns:
      the current ordering scheme

    • getNside

      public int getNside()
      Returns the current Nside parameter.
      Returns:
      the current Nside parameter

    • getNpix

      public long getNpix()
      Returns the total number of pixels in the pixelisation.
      Returns:
      the current total number of pixels

    • setScheme

      public void setScheme(Scheme scheme_in) throws Exception
      Adjusts the object to scheme.
      Parameters:
      scheme_in - the new ordering scheme
      Throws:
      Exception

    • getOrder

      public int getOrder()
      Returns the current order parameter.
      Returns:
      the current map order parameter.

    • ang2pix

      public long ang2pix(Pointing ptg) throws Exception
      Returns the pixel which contains the supplied Pointing.
      Parameters:
      ptg - the requested location on the sphere.
      Returns:
      the pixel number containing the location.
      Throws:
      Exception

    • pix2ang

      public Pointing pix2ang(long pix) throws Exception
      Returns the Pointing corresponding to the center of the supplied pixel.
      Parameters:
      pix - the requested pixel number.
      Returns:
      the pixel's center coordinates.
      Throws:
      Exception

    • vec2pix

      public long vec2pix(Vec3 vec) throws Exception
      Returns the pixel which contains the supplied Vec3.
      Parameters:
      vec - the requested location on the sphere (need not be normalized).
      Returns:
      the pixel number containing the location.
      Throws:
      Exception

    • pix2vec

      public Vec3 pix2vec(long pix) throws Exception
      Returns the normalized 3-vector corresponding to the center of the supplied pixel.
      Parameters:
      pix - the requested pixel number.
      Returns:
      the pixel's center coordinates.
      Throws:
      Exception

    • ring2nest

      public long ring2nest(long ipring) throws Exception
      Returns nested pixel number for the supplied ring pixel number.
      Parameters:
      ipring - the requested pixel number in RING scheme.
      Returns:
      the corresponding pixel number in NESTED scheme.
      Throws:
      Exception

    • nest2ring

      public long nest2ring(long ipnest) throws Exception
      Returns ring pixel number for the supplied nested pixel number.
      Parameters:
      ipnest - the requested pixel number in NESTED scheme.
      Returns:
      the corresponding pixel number in RING scheme.
      Throws:
      Exception

    • loc2pix

      protected long loc2pix(healpix.essentials.Hploc loc)

    • zphi2pix

      public long zphi2pix(Zphi zphi)
      Returns the pixel which contains the supplied Zphi.
      Parameters:
      zphi - the requested location on the sphere.
      Returns:
      the pixel number containing the location.

    • pix2loc

      protected healpix.essentials.Hploc pix2loc(long pix)

    • pix2zphi

      public Zphi pix2zphi(long pix)
      Returns the Zphi corresponding to the center of the supplied pixel.
      Parameters:
      pix - the requested pixel number.
      Returns:
      the pixel's center coordinates.

    • neighbours

      public long[] neighbours(long ipix) throws Exception
      Returns the neighboring pixels of ipix. This method works in both RING and NEST schemes, but is considerably faster in the NEST scheme.
      Parameters:
      ipix - the requested pixel number.
      Returns:
      array with indices of the neighboring pixels. The returned array contains (in this order) the pixel numbers of the SW, W, NW, N, NE, E, SE and S neighbor of ipix. If a neighbor does not exist (this can only happen for the W, N, E and S neighbors), its entry is set to -1.
      Throws:
      Exception

    • maxPixrad

      public double maxPixrad()
      Returns the maximum angular distance between a pixel center and its corners.
      Returns:
      maximum angular distance between a pixel center and its corners.

    • ring2z

      public double ring2z(long ring)
      Returns the z-coordinate (equivalent to the cosine of the colatitude) for the requested ring. This method also accepts the not-really-existing ring indices 0 and 4*Nside, which correspond to North and South Poles, respectively.
      Parameters:
      ring - ring index: the northernmost ring in the map has index 1; ring indices are increasing towards the South pole.
      Returns:
      z-coordinate of the ring.

    • ring2theta

      public double ring2theta(long ring)
      Returns the colatitude for the requested ring. This method also accepts the not-really-existing ring indices 0 and 4*Nside, which correspond to North and South Poles, respectively.
      Parameters:
      ring - ring index: the northernmost ring in the map has index 1; ring indices are increasing towards the South pole.
      Returns:
      z-coordinate of the ring.

    • queryStrip

      public RangeSet queryStrip(double theta1, double theta2, boolean inclusive) throws Exception
      Returns a range set of pixels whose centers lie within a given latitude range (if inclusive==false), or which overlap with this range (if inclusive==true).

      The latitude range is defined as follows:

      • if theta1<theta2, it is the range between theta1 and theta2
      • otherwise it is the range between 0 and theta2, and between theta1 and pi.
      This method currently only works in the RING scheme.
      Throws:
      Exception

    • queryDisc

      public RangeSet queryDisc(Pointing ptg, double radius) throws Exception
      Returns a range set of pixels whose centers lie within a given disk.

      This method is more efficient in the RING scheme.

      Parameters:
      ptg - the angular coordinates of the disk center
      radius - the radius (in radians) of the disk
      Returns:
      the requested set of pixel number ranges
      Throws:
      Exception

    • queryDiscInclusive

      public RangeSet queryDiscInclusive(Pointing ptg, double radius, int fact) throws Exception
      Returns a range set of pixels which overlap with a given disk.

      This method is more efficient in the RING scheme.

      This method may return some pixels which don't overlap with the polygon at all. The higher fact is chosen, the fewer false positives are returned, at the cost of increased run time.

      Parameters:
      ptg - the angular coordinates of the disk center
      radius - the radius (in radians) of the disk
      fact - The overlapping test will be done at the resolution fact*nside. For NESTED ordering, fact must be a power of 2, else it can be any positive integer. A typical choice would be 4.
      Returns:
      the requested set of pixel number ranges
      Throws:
      Exception

    • queryPolygon

      public RangeSet queryPolygon(Pointing[] vertex) throws Exception
      Returns a range set of pixels whose centers lie within the convex polygon defined by the vertex array.

      This method is more efficient in the RING scheme.

      Parameters:
      vertex - an array containing the vertices of the requested convex polygon.
      Returns:
      the requested set of pixel number ranges
      Throws:
      Exception

    • queryPolygonInclusive

      public RangeSet queryPolygonInclusive(Pointing[] vertex, int fact) throws Exception
      Returns a range set of pixels that overlap with the convex polygon defined by the vertex array.

      This method is more efficient in the RING scheme.

      This method may return some pixels which don't overlap with the polygon at all. The higher fact is chosen, the fewer false positives are returned, at the cost of increased run time.

      Parameters:
      vertex - an array containing the vertices of the requested convex polygon.
      fact - The overlapping test will be done at the resolution fact*nside. For NESTED ordering, fact must be a power of 2, else it can be any positive integer. A typical choice would be 4.
      Returns:
      the requested set of pixel number ranges
      Throws:
      Exception

    • pix2ring

      public long pix2ring(long pix)
      Compute ring index from pixel number. Works in both RING and NESTED schemes
      Parameters:
      pix - pixel number
      Returns:
      ring index (1 to 4Nside-1)

    • boundaries

      public Vec3[] boundaries(long pix, int step) throws Exception
      Returns a set of points along the boundary of the given pixel. Step 1 gives 4 points on the corners. The first point corresponds to the northernmost corner, the subsequent points follow the pixel boundary through west, south and east corners.
      Parameters:
      pix - pixel index number
      step - the number of returned points is 4*step
      Returns:
      Vec3 for each point
      Throws:
      Exception