This routine returns
information about a single standard sky tile for a named JCMT instrument (specified by parameter
ITILE). This includes the RA and Dec. of the tile centre, the tile size, the tile WCS, and whether the
NDF containing the accumulated co-added data for the tile currently exists. If not, there is
an option to create it and fill it with zeros (see parameter CREATE). In addition, an NDF
can be created containing the tile index at every point on the whole sky (see parameter
ALLSKY).
Also, the bounds of the overlap in pixel indices between the tile and a specified NDF or Region can be
found (see parameter TARGET).
The environment variable JSA_TILE_DIR should be defined prior to using this command, and should
hold the path to the directory in which the NDFs containing the accumulated co-added data for each
tile are stored. Tiles for a specified instrument will be stored within a sub-directory of this directory
(see parameter INSTRUMENT). If JSA_TILE_DIR is undefined, the current directory is used.
ALLSKY = NDF (Write)
If not null (!), this is the name of a new 2D NDF to create
holding the tile index at every point on the sky. The pixel size in this image is much larger than in an
individual tile in order to keep the NDF size managable. Each pixel holds the integer index of a
tile. Pixels that have no corresponding tile hold a bad value. [!]
CREATE = _LOGICAL
(Read)
Indicates if the NDF containing co-added data for the tile should be created if
it does not already exist. If TRUE, and if the tile’ s NDF does not exist on entry to this
command, a new NDF will be created for the tile and filled with zeros. The instrument
subdirectory within the JSA_TILE_DIR directory will be created if it does not already exist.
[FALSE]
DECCEN = _DOUBLE (Write)
An output parameter to which is written the ICRS
Declination of the tile centre, in radians.
EXISTS = _LOGICAL (Write)
An output parameter
that is set TRUE if the NDF containing co-added data for the tile existed on entry to this
command (FALSE otherwise).
HEADER = LITERAL (Read)
The name of a new text file in
which to store the WCS and extent of the tile in the form of a set of FITS-WCS headers. [!]
INSTRUMENT = LITERAL (Read)
The JCMT instrument (different instruments have different tiling
schemes and pixel sizes). The following instrument names are recognised (unambiguous
abbreviations may be supplied): " SCUBA-2(450)" , " SCUBA-2(850)" , " ACSIS" , " DAS" .
NDFs containing co-added data for the selected instrument reside within a corresponding
sub-directory of the directory specified by environment variable JSA_TILE_DIR. These
sub-directories are called " scuba2-450" , " scuba2-850" , " acsis" and " das" .
ITILE =
_INTEGER (Read)
The index of the tile about which information is required. The first
tile has index 0. The largest allowed tile index is always returned in output parameter
MAXTILE. If a null (!) value is supplied for ITILE, the MAXTILE parameter is still written, but
the command will then exit immediately without further action (and without error).
LBND( 2 ) = _INTEGER (Write)
An output parameter to which are written the lower
pixel bounds of the NDF containing the co-added data for the tile.
LOCAL = _LOGICAL
(Read)
If TRUE, the FITS reference point is put at the centre of the tile. Otherwise, it is
put at RA=0 Dec=0. [FALSE]
MAXTILE = _INTEGER (Write)
An output parameter to
which is written the largest tile index associated with the instrument specified by parameter
INSTRUMENT.
PROJ = LITERAL (Read)
Determines the JSA projection to use. The allowed
values are " HPX" (HPX projection centred on RA=0h), " HPX12" (HPX projection centred
on RA=12h), " XPHN" (XPH projection centred on the north pole) and " XPHS" (XPH
projection centred on the south pole). A null (!) value causes " HPX" to be used. [" HPX" ]
RACEN = LITERAL (Write)
An output parameter to which is written the ICRS Right
Ascension of the tile centre, in radians.
REGION = LITERAL (Read)
The name of a new text
file in which to store the WCS and extent of the tile in the form of an AST Region. [!]
SIZE = _DOUBLE (Write)
An output parameter to which is written the arc-length of
each side of a square bounding box for the tile, in radians.
TARGET = LITERAL (Read)
Defines the region of interest. The pixel index bounds of the area of the specified tile that
overlaps this region are found and reported (see parameter TLBND and TUBND). The
value supplied for TARGET can be either the name of a text file containing an AST Region,
or the path for an NDF, in which case a Region is created that covers the region of sky
that maps onto the rectangular pixel grid of the NDF. [!]
TILENDF = LITERAL (Write)
An output parameter to which is written the full path to the NDF containing co-added
data for the tile. Note, it is not guaranteed that this NDF exists on exit from this command
(see parameters EXISTS and CREATE).
TLBND( 2 ) = _INTEGER (Write)
An output
parameter to which are written the lower pixel bounds of the area of the tile NDF that overlaps
the region specified by parameter TARGET. If there is no overlap, the TLBND values are
returned greater than the TUBND values.
TUBND( 2 ) = _INTEGER (Write)
An output
parameter to which are written the upper pixel bounds of the area of the tile NDF that overlaps
the region specified by parameter TARGET. If there is no overlap, the TLBND values are
returned greater than the TUBND values.
UBND( 2 ) = _INTEGER (Write)
An output
parameter to which are written the upper pixel bounds of the NDF containing the co-added
data for the tile.