ERRCLIP - Removes pixels with large errors from an NDF

Description:

This application produces a copy of the input NDF  in which pixels with errors greater than a specified limit are set invalid in both DATA and VARIANCE  components. The error limit may be specified as the maximum acceptable standard deviation (or variance), or the minimum acceptable signal-to-noise ratio.

Usage:

errclip in out limit [mode]

Parameters:

IN = NDF (Read)

The input NDF. An error is reported if it contains no VARIANCE component.

LIMIT = _DOUBLE (Read)

Either the maximum acceptable standard deviation or variance value, or the minimum acceptable signal-to-noise ratio (depending on the value given for MODE). It must be positive.

MODE = LITERAL (Read)

Determines how the value supplied for LIMIT is to be interpreted: "Sigma" for a standard deviation, "Variance" for variance, or "SNR" for minimum signal-to-noise ratio. ["Sigma"]

OUT = NDF (Write)

The output NDF.

Examples:

errclip m51 m51_good 2.0

The NDF m51_good is created holding a copy of m51 in which all pixels with standard deviation greater than 2 are set invalid.

errclip m51 m51_good 2.0 snr

The NDF m51_good is created holding a copy of m51 in which all pixels with a signal-to-noise ratio less than 2 are set invalid.

errclip m51 m51_good mode=v limit=100

The NDF m51_good is created holding a copy of m51 in which all pixels with a variance greater than 100 are set invalid.

Notes:

• The limit and the number of rejected pixels are reported.

• A pair of output data and variance values are set bad when either of the input data or variances values is bad.

• For MODE="SNR" the comparison is with respect to the absolute data value.

Related Applications

KAPPA: FFCLEAN, PASTE, SEGMENT, SETMAGIC, THRESH.

Implementation Status:

• This routine correctly processes the AXIS, DATA, QUALITY, VARIANCE, LABEL, TITLE, UNITS, WCS, and HISTORY  components of an NDF data structure and propagates all extensions.

• Processing of bad pixels and automatic quality masking are supported.

• All non-complex numeric data types can be handled. The output NDF has the same numeric type as the input NDF. However, all internal calculations are performed in double precision.