NAME¶
stilts-pixfoot - Generates Multi-Order Coverage maps
SYNOPSIS¶
stilts pixfoot [ifmt=<in-format>]
[istream=true|false] [in=<table>]
[icmd=<cmds>] [order=<int-value>]
[ra=<expr>] [dec=<expr>]
[radius=<expr>] [mocfmt=fits|json]
[out=<out-file>]
DESCRIPTION¶
pixfoot takes a list of sky positions from an input table
and generates a pixel map describing a sky region which includes them all.
Currently the output is to a format known as a Multi-Order Coverage map
(MOC), which is a HEALPix-based format composed of a list of HEALPix pixels
of different sizes, which can efficiently describe complex regions. Other
output formats may be introduced in the future.
See also the Coverage class for MOC-related functions.
OPTIONS¶
- ifmt=<in-format>
Specifies the format of the input table as specified by
parameter
in. The known formats are listed in SUN/256. This flag can be
used if you know what format your table is in. If it has the special value
(auto) (the default), then an attempt will be made to detect the format
of the table automatically. This cannot always be done correctly however, in
which case the program will exit with an error explaining which formats were
attempted. This parameter is ignored for scheme-specified tables.
- istream=true|false
If set true, the input table specified by the
in
parameter will be read as a stream. It is necessary to give the
ifmt
parameter in this case. Depending on the required operations and processing
mode, this may cause the read to fail (sometimes it is necessary to read the
table more than once). It is not normally necessary to set this flag; in most
cases the data will be streamed automatically if that is the best thing to do.
However it can sometimes result in less resource usage when processing large
files in certain formats (such as VOTable). This parameter is ignored for
scheme-specified tables.
- in=<table>
The location of the input table. This may take one of the
following forms:
- A filename.
- A URL.
- The special value "-", meaning standard input. In this
case the input format must be given explicitly using the ifmt
parameter. Note that not all formats can be streamed in this way.
- A scheme specification of the form
:<scheme-name>:<scheme-args>.
- A system command line with either a "<" character at
the start, or a "|" character at the end
("<syscmd" or "syscmd|"). This
executes the given pipeline and reads from its standard output. This will
probably only work on unix-like systems.
In any case, compressed data in one of the supported compression formats (gzip,
Unix compress or bzip2) will be decompressed transparently.
- icmd=<cmds>
Specifies processing to be performed on the input table
as specified by parameter
in, before any other processing has taken
place. The value of this parameter is one or more of the filter commands
described in SUN/256. If more than one is given, they must be separated by
semicolon characters (";"). This parameter can be repeated multiple
times on the same command line to build up a list of processing steps. The
sequence of commands given in this way defines the processing pipeline which
is performed on the table.
Commands may alteratively be supplied in an external file, by
using the indirection character '@'. Thus a value of
"@filename" causes the file filename to be read for
a list of filter commands to execute. The commands in the file may be
separated by newline characters and/or semicolons, and lines which are blank
or which start with a '#' character are ignored.
- order=<int-value>
Maximum HEALPix order for the MOC. This defines the
maximum resolution of the output coverage map. The angular resolution
corresponding to order k is approximately 180/sqrt(3.Pi)/2^k (3520*2^-k
arcmin).
- ra=<expr>
Right ascension in degrees for the position of each row
of the input table. This may simply be a column name, or it may be an
algebraic expression calculated from columns as explained in SUN/256. If left
blank, an attempt is made to guess from UCDs, column names and unit
annotations what expression to use.
- dec=<expr>
Declination in degrees for the position of each row of
the input table. This may simply be a column name, or it may be an algebraic
expression calculated from columns as explained in SUN/256. If left blank, an
attempt is made to guess from UCDs, column names and unit annotations what
expression to use.
- radius=<expr>
Expression which evaluates to the radius in degrees of
the cone at each row of the input table. The default is "
0",
which treats each position as a point rather than a cone, but a constant or an
expression as described in SUN/256 may be used instead.
- mocfmt=fits|json
Determines the output format for the MOC file.
- out=<out-file>
The location of the output file. This is usually a
filename to write to. If it is equal to the special value "-" the
output will be written to standard output.
AUTHOR¶
Mark Taylor (Bristol University)
