Class Coverage

java.lang.Object
uk.ac.starlink.ttools.func.Coverage
public class Coverage extends Object
Functions related to coverage and footprints.

One coverage standard is Multi-Order Coverage maps, described at http://www.ivoa.net/Documents/MOC/. MOC positions are always defined in ICRS equatorial coordinates.

MOCs may be specified using a string argument of the functions in one of the following ways:

  • The filename of a MOC FITS file
  • The URL of a MOC FITS file
  • The identifier of a VizieR table, for instance "V/139/sdss9" (SDSS DR9)
  • An ASCII MOC string, for instance "1/1 2 4 2/12-14 21 23 25 8/"

A list of all the MOCs available from VizieR can currently be found at http://alasky.u-strasbg.fr/footprints/tables/vizier/. You can search for VizieR table identifiers from the VizieR web page (http://vizier.u-strasbg.fr/); note you must use the table identifier (like "V/139/sdss9") and not the catalogue identifier (like "V/139").

Since:
29 May 2012
Author:
Mark Taylor

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final double
    SPHERE_SQDEG
    The number of square degrees on the sphere, approx 41253.
    static final double
    SPHERE_STERADIAN
    The number of steradians on the sphere, 4 PI.

  • Method Summary

    Modifier and Type
    Method
    Description
    static boolean
    inMoc(String moc, double ra, double dec)
    Indicates whether a given sky position falls strictly within a given MOC (Multi-Order Coverage map).
    static double
    mocSkyProportion(String moc)
    Returns the proportion of the sky covered by a given MOC.
    static long
    mocTileCount(String moc)
    Returns the number of unique tiles within a given MOC.
    static long
    mocUniq(int order, long index)
    Converts a HEALPix order and and tile index into a UNIQ-encoded integer as used in MOC encoding.
    static boolean
    nearMoc(String moc, double ra, double dec, double distanceDeg)
    Indicates whether a given sky position either falls within, or is within a certain distance of the edge of, a given MOC (Multi-Order Coverage map).
    static long
    uniqToIndex(long uniq)
    Extracts the HEALPix pixel index from a UNIQ-encoded integer as used in MOC encoding.
    static int
    uniqToOrder(long uniq)
    Extracts the HEALPix order from a UNIQ-encoded integer as used in MOC encoding.

    Methods inherited from class Object

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

  • Field Details

    • SPHERE_STERADIAN

      public static final double SPHERE_STERADIAN
      The number of steradians on the sphere, 4 PI.
      See Also:

    • SPHERE_SQDEG

      public static final double SPHERE_SQDEG
      The number of square degrees on the sphere, approx 41253.
      See Also:

  • Method Details

    • inMoc

      public static boolean inMoc(String moc, double ra, double dec)
      Indicates whether a given sky position falls strictly within a given MOC (Multi-Order Coverage map). If the given moc value does not represent a MOC (for instance no file exists or the file/string is not in MOC format) a warning will be issued the first time it's referenced, and the result will be false.
      Parameters:
      moc - a MOC identifier; a filename, a URL, a VizieR table name, or an ASCII MOC string
      ra - ICRS right ascension in degrees
      dec - ICRS declination in degrees
      Returns:
      true iff the given position falls within the given MOC

    • nearMoc

      public static boolean nearMoc(String moc, double ra, double dec, double distanceDeg)
      Indicates whether a given sky position either falls within, or is within a certain distance of the edge of, a given MOC (Multi-Order Coverage map). If the given moc value does not represent a MOC (for instance no file exists or the file/string is not in MOC format) a warning will be issued the first time it's referenced, and the result will be false.
      Parameters:
      moc - a MOC identifier; a filename, a URL, a VizieR table name, or an ASCII MOC string
      ra - ICRS right ascension in degrees
      dec - ICRS declination in degrees
      distanceDeg - permitted distance from MOC boundary in degrees
      Returns:
      true iff the given position is within distance degrees of the given MOC

    • mocSkyProportion

      public static double mocSkyProportion(String moc)
      Returns the proportion of the sky covered by a given MOC.

      If the given moc value does not represent a MOC (for instance no file exists or the file/string is not in MOC format) a warning will be issued the first time it's referenced, and the result will be NaN.

      Parameters:
      moc - a MOC identifier; a filename, a URL, a VizieR table name, or an ASCII MOC string
      Returns:
      a fractional value in the range 0..1

    • mocTileCount

      public static long mocTileCount(String moc)
      Returns the number of unique tiles within a given MOC.

      If the given moc value does not represent a MOC (for instance no file exists or the file/string is not in MOC format) a warning will be issued the first time it's referenced, and the result will be 0.

      Parameters:
      moc - a MOC identifier; a filename, a URL, a VizieR table name, or an ASCII MOC string
      Returns:
      number of tiles in the MOC

    • mocUniq

      public static long mocUniq(int order, long index)
      Converts a HEALPix order and and tile index into a UNIQ-encoded integer as used in MOC encoding. The result is index + 4**(1+order).

      If the order or index are out of bounds, behaviour is undefined.

      Parameters:
      order - HEALPix order, in range 0..29
      index - tile index within the given level
      Returns:
      uniq-encoded value

    • uniqToOrder

      public static int uniqToOrder(long uniq)
      Extracts the HEALPix order from a UNIQ-encoded integer as used in MOC encoding.

      If the supplied value is not a legal UNIQ integer, behaviour is undefined.

      Parameters:
      uniq - uniq-encoded value
      Returns:
      HEALPix order

    • uniqToIndex

      public static long uniqToIndex(long uniq)
      Extracts the HEALPix pixel index from a UNIQ-encoded integer as used in MOC encoding.

      If the supplied value is not a legal UNIQ integer, behaviour is undefined.

      Parameters:
      uniq - uniq-encoded value
      Returns:
      pixel index

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