10.7.7 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.

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").

inMoc( moc, ra, 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 (String): a MOC identifier; a filename, a URL, a VizieR table name, or an ASCII MOC string
  • 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( moc, 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 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 (String): a MOC identifier; a filename, a URL, a VizieR table name, or an ASCII MOC string
  • 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