.TH MDIFFEXEC 1 "Dec 2016" "Montage 5" "Montage"
.SH NAME
mDiffExec \- Re-project and mosaic your images, with background rectification

.SH SYNOPSIS
mDiffExec [\-p \fIprojdir\fP] [\-d] [\-n(o-areas)] [\-s \fIstatusfile\fP] diffs.tbl template.hdr diffdir

.SH DESCRIPTION
Runs \fBmDiff\fP on all the pairs identified by \fBmOverlaps.\fP

.SH OPTIONS
.TP
\-p \fIprojdir\fP
Specifies path to the directory containing reprojected input images.
.TP
\-d
Turns on debugging.
.TP
\-n
No-area-images flag. Creates difference image without requiring \fB_area\fP FITS images
.TP
\-s \fIstatusfile\fP
Output and errors are sent to \fIstatusfile\fP instead of to stdout

.SH ARGUMENTS
.TP
diffs.tbl
Table generated by \fBmOverlaps for the images in \fBprojdir\fP.\fP
.TP
template.hdr
FITS header template for output files.
.TP
diffdir
Path to output files.

.SH RESULT
FITS images representing the differences for each pair of overlapping images.  \fInimages\fP is the total number of images successfully processed, and \fInfailed\fP is the number of images that failed.  The most likely cause of failure is that the FITS images overlapped, but only in areas where they contained blank pixels (especially common in images with large degree of rotation).

.SH MESSAGES
.TP
OK
[struct stat="OK", count=\fInimages\fP, failed=\fInfailed\fP]
.TP
ERROR
MPI initialization failed
.TP
ERROR
Cannot open status file: \fIstatusfile\fP
.TP
ERROR
Cannot access \fIdiffdir\fP
.TP
ERROR
\fIdiffdir\fP is not a directory
.TP
ERROR
Invalid image metadata file: \fIfilename\fP
.TP
ERROR
Need columns: cntr1 cntr2 plus minus diff
.TP
ERROR
\fImDiff error\fP

.SH EXAMPLES
.PP
First, diffs.tbl is generated using mOverlaps.  Then mDiff can be run on reprojected images, using this template.hdr.
.TP
$ mDiffExec \-n \-p projdir projdir/diffs.tbl template.hdr diffdir
[struct stat="OK", count=42, failed=0]

.SH BUGS
The drizzle algorithm has been implemented but has not been tested
in this release.
.PP
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"]
.PP
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.

.SH COPYRIGHT
2001-2015 California Institute of Technology, Pasadena, California
.PP
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."
.PP
The Montage distribution includes an adaptation of the MOPEX algorithm
developed at the Spitzer Science Center.