---
name: "mSubset"
section: "1"
platform: "linux"
package: "montage"
version: "4.0+dfsg-3+b3"
release: "Debian 9 (Stretch)"
platforms: ["linux"]
url: "https://new.carta.tech/mSubset"
---

# mSubset(1)

Filter an image metadata table down to those records representing FITS files that overlap a footprint on the sky

## NAME

mSubset - Filter an image metadata table down to those records representing FITS files that overlap a footprint on the sky

## SYNOPSIS

mSubset \[-d *level*\] \[-f\] \[-s *statusfile*\] images.tbl template.hdr subset.tbl

## DESCRIPTION

Generates a table of images that is a subset of the input table, containing only those images that cover the area defined by a given FITS header.

## OPTIONS

- \-d *level*

  Turns on debugging to the specified level (1-3).

- \-f

  Fast mode - input file must include corners (-c flag in mImgtbl) to utilize this mode.

- \-s *statusfile*

  Output and errors are sent to *statusfile* instead of to stdout

## ARGUMENTS

- images.tbl

  ASCII table (generated by **mImgtbl**) containing metadata for image collection.

- template.hdr

  FITS header template defining the area of interest.

- subset.tbl

  Path to output table, which will contain only those FITS images covering the area defined by *template.hdr*.

## RESULT

**\[struct stat="OK", count=***nin***, nmatches=***nout***\]**

*where nin is the number of rows found in images.tbl, and nmatches is the number of rows in subset.tbl, which includes only those images that overlap the area defined by template.hdr.*

## BUGS

*The drizzle algorithm has been implemented but has not been tested* *in this release.*

*If a header template contains carriage returns (i.e., created/modified* *on a Windows machine), the cfitsio library will be unable to read it* *properly, resulting in the error: \[struct stat="ERROR", status=207,* *msg="illegal character in keyword"\]*

*It is best for the background correction algorithms if the area* *described in the header template completely encloses all of the input* *images in their entirety. If parts of input images are "chopped off"* *by the header template, the background correction will be affected. We* *recommend you use an expanded header for the reprojection and* *background modeling steps, returning to the originally desired header* *size for the final coaddition. The default background matching assumes* *that there are no non-linear background variations in the individual* *images (and therefore in the overlap differences). If there is any* *uncertainty in this regard, it is safer to turn on the "level only"* *background matching (the "-l" flag in mBgModel.*

## COPYRIGHT

*2001-2015 California Institute of Technology, Pasadena, California*

*If your research uses Montage, please include the following* *acknowledgement: "This research made use of Montage. It is funded by* *the National Science Foundation under Grant Number ACI-1440620, and* *was previously funded by the National Aeronautics and Space* *Administration's Earth Science Technology Office, Computation* *Technologies Project, under Cooperative Agreement Number NCC5-626* *between NASA and the California Institute of Technology."*

*The Montage distribution includes an adaptation of the MOPEX algorithm* *developed at the Spitzer Science Center.*