## Class `Coverage`

Description:
  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 https://alasky.cds.unistra.fr/footprints/tables/vizier/. You can search for VizieR table identifiers from the VizieR web page (https://vizier.cds.unistra.fr/); note you must use the table identifier (like "`V/139/sdss9`") and not the catalogue identifier (like "`V/139`").