mFitplane - Use least squares to fit a plane to an image

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

       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.

       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.

Montage 5                                           Dec 2016                                        MFITPLANE(1)

       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.

       $ 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]

       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  FITSlibraryerror

       ERROR  generalerror

       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()

       mFitplane - Use least squares to fit a plane to an image

       -b border
              Number of border pixels to ignore at edges of image.

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

       -l     Level only: don't fit a slope; just get a zero level.

       -s statusfile
              Output and errors are written to statusfile instead of stdout.

       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.

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