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### B.1.6 Coverage

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.

MOC locations may be given as either the filename or the URL of a MOC FITS file. Alternatively, they may be the identifier of a VizieR table, for instance "`V/139/sdss9`" (SDSS DR9). 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`").

`inMoc( mocLocation, ra, dec )`
  Indicates whether a given sky position falls strictly within a given MOC (Multi-Order Coverage map). If the given `mocLocation` value does not represent a MOC (for instance no file exists or the file is not in MOC format) a warning will be issued the first time it's referenced, and the result will be false.

  - Parameters:
    - `mocLocation` (String): location of a FITS MOC file: a filename, a URL, or a VizieR table name
    - `ra` (floating point): ICRS right ascension in degrees
    - `dec` (floating point): ICRS declination in degrees
  - Return value
    - (boolean): true iff the given position falls within the given MOC
`nearMoc( mocLocation, ra, dec, 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 `mocLocation` value does not represent a MOC (for instance no file exists or the file is not in MOC format) a warning will be issued the first time it's referenced, and the result will be false.

  - Parameters:
    - `mocLocation` (String): location of a FITS MOC file: a filename, a URL, or a VizieR table name
    - `ra` (floating point): ICRS right ascension in degrees
    - `dec` (floating point): ICRS declination in degrees
    - `distanceDeg` (floating point): permitted distance from MOC boundary in degrees
  - Return value
    - (boolean): true iff the given position is within `distance` degrees of the given MOC

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk