man mFitplane (1): Use least squares to fit a plane to an image

SYNOPSIS

mFitplane [-b border] [-d level] [-s statusfile] in.fits

DESCRIPTION

Uses least squares to fit a plane (excluding outlier pixels) to an image. It is used on the difference images generated using mDiff or mDiffExec.

OPTIONS

-b border: Number of border pixels to ignore at edges of image.
-d level: Turns on debugging to the specified level (1-3).
-s statusfile: Output and errors are written to statusfile instead of stdout.

ARGUMENTS

in.fits: Input FITS file is a difference file between two other FITS files, as can be generated using mDiff.

RESULT

The plane fit to the image is of the form:

fit = A*x + B*y + C

where x is the "horizontal" pixel offset from CRPIX1 in the FITS header and y is the "vertical" offset from CRPIX2. Since all reprojected images use the same reference pixel, this is a uniform definition for x,y for the whole image set.

The fitting is a simple least squares, with an iterative loop to exclude points more than 2 sigma (sigma defined as the rms from the previous loop).

The rms output is the value computed above. The xmin, ... ymax output correspond to the range of x,y values found while fitting. The rms is for information only but the xmin, ... ymax are used in the background fitting (mBgModel). crpix1 and crpix2 are the reference pixels for each axis, as determined from the FITS header.

MESSAGES

OK: [struct stat="OK", a=A, b=B, c=C, crpix1=crpix1, crpix2=crpix2, xmin=xmin, xmax=xmax, ymin=ymin, ymax=ymax, xcenter=xcenter, ycenter=ycenter, npixel=npixel, rms=rms, boxx=boxx, boxy=boxy, boxwidth=boxwidth, boxheight=boxheight, boxang=boxang]
ERROR: Argument to -b (string) cannot be interpreted as an integer
ERROR: Cannot open status file: statusfile
ERROR: Image file filename missing or invalid FITS
ERROR: FITS library error
ERROR: general error
WARNING: Too few pixels to fit
WARNING: Too few pixels for bounding box
WARNING: Singular Matrix-1
WARNING: Singular Matrix-2
WARNING: allocation failure in ivector()

EXAMPLES

$ mFitplane 2mass-atlas-990322n-j0640266.fits: [struct stat="OK", a=-8.9198e-11, b=-2.54173e-10, c=5.24277e-05, crpix1=808, crpix2=212.5, xmin=-808, xmax=167, ymin=-210.5, ymax=638.5, xcenter=-320.871, ycenter=213.014, npixel=314299, rms=0.393003, boxx=-320.92, boxy=212.424, boxwidth=835.421, boxheight=509.274, boxang=-29.5537]

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.