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### B.8.1 Usage

The usage of `pixfoot` is

       stilts <stilts-flags> pixfoot ifmt=<in-format> istream=true|false
                                     icmd=<cmds> order=<int-value> ra=<expr>
                                     dec=<expr> radius=<expr> mocfmt=fits|json
                                     out=<out-file>
                                     [in=]<table>

If you don't have the `stilts` script installed, write "`java -jar stilts.jar`" instead of "`stilts`" - see Section 3. The available `<stilts-flags>` are listed in Section 2.1. For programmatic invocation, the Task class for this command is `uk.ac.starlink.ttools.task.PixFootprint`.

Parameter values are assigned on the command line as explained in Section 2.3. They are as follows:

`dec = <expr>` (String)
  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 Section 10. If left blank, an attempt is made to guess from UCDs, column names and unit annotations what expression to use.
`icmd = <cmds>` (ProcessingStep[])
  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 Section 6.1. 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 alternatively 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. A backslash character '`\`' at the end of a line joins it with the following line.

`ifmt = <in-format>` (String)
  Specifies the format of the input table as specified by parameter `in`. The known formats are listed in Section 5.1.1. 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.

  [Default: `(auto)`]

`in = <table>` (StarTable)
  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.
`istream = true|false` (Boolean)
  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.

  [Default: `false`]

`mocfmt = fits|json` (MocFormat)
  Determines the output format for the MOC file.

  [Default: `fits`]

`order = <int-value>` (Integer)
  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).

  [Default: `13`]

`out = <out-file>` (uk.ac.starlink.util.Destination)
  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.

  [Default: `-`]

`ra = <expr>` (String)
  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 Section 10. If left blank, an attempt is made to guess from UCDs, column names and unit annotations what expression to use.
`radius = <expr>` (String)
  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 Section 10 may be used instead.

  [Default: `0`]

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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk