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STILTS-PIXFOOT(1) Stilts commands STILTS-PIXFOOT(1)

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.

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).

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 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.

SEE ALSO

stilts(1)

If the package stilts-doc is installed, the full documentation SUN/256 is available in HTML format:
file:///usr/share/doc/stilts-doc/sun256/index.html

VERSION

STILTS version 3.1-5-debian

This is the Debian version of Stilts, which lack the support of some file formats and network protocols. For differences see
file:///usr/share/doc/stilts/README.Debian

AUTHOR

Mark Taylor (Bristol University)
Mar 2017