Provided by: montage_5.0+dfsg-1_amd64 
NAME
mDiff - Calculates the difference between a pair of overlapping images
SYNOPSIS
mDiff [-d level] [-n(o-areas)] [-s statusfile] in1.fits in2.fits out.fits template.hdr
DESCRIPTION
mDiff calculates a simple difference between a single pair of overlapping images. This is meant for use
on reprojected images where the pixels already line up exactly. mDiff analyzes an image metadata table to
determine a list of overlapping images. Each image is compared with every other image to determine all
overlapping image pairs. A pair of images are deemed to overlap if any pixel around the perimeter of one
image falls within the boundary of the other image.
OPTIONS
-d level
Turns on debugging to the specified level (1-4).
-n No-area-images flag. Creates difference image without requiring pixel area FITS image
-z factor
Scale second image by factor before subtracting.
-s statusfile
Output and errors are sent to statusfile instead of to stdout
ARGUMENTS
in1.fits
First input FITS file. (Also needs area image in1_area.fits, or use -n flag)
in2.fits
Second input FITS file.(Also needs area image in2_area.fits, or use -n flag)
out.fits
Difference FITS image to be generated.
template.hdr
FITS header template used to generate output image.
RESULT
FITS image and area image representing the difference in the overlap region.
MESSAGES
OK [struct stat="OK"]
ERROR Cannot open status file: statusfile
ERROR Images don't overlap
ERROR All pixels are blank
ERROR Template file not found
ERROR FITS library error
ERROR general error
EXAMPLES
$ mDiff proj/in1.fits proj/in2.fits output/diff.fits template.hdr
[struct stat="OK"]
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.