NAME

       mTANHdr - Determine if there would be an equivalent distorted TAN projection

SYNOPSIS

       mTANHdr [-d] [-o order][-i maxiter][-t tolerance][-s statusfile] orig.hdr new.hdr

DESCRIPTION

       Analyzes a template file and determines if there would be an adequate equivalent distorted
       TAN projection, within a specified tolerance,  and  outputs  the  alternate  header.  This
       header  can  be  used  in  conjunction  with mProjectPP to produce a TAN plane image. This
       process is considerably faster than projecting with the general purpose tool mProject.

       The output header is a FITS header template containing a TAN  projection  with  polynomial
       focal plane distortions. (Link to an example output header)

       mTANHdr  is  most  suitable  for  projections  which  can be approximated by tangent-plane
       projections (TAN, SIN, ZEA, STG, ARC),  and  is  also  therefore  not  suited  for  images
       covering large portions of the sky.

OPTIONS

       -d     Print additional debugging information to stdout.

       -o order
              Order of output header polynomial focal plane distortions (default = 4)

       -i maxiter
              Maximum number of iteration attempts to produce header (default = 50)

       -t tolerance
              Distortion tolerance value for acceptable output (default = 0.01)

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

ARGUMENTS

       orig.hdr
              Input FITS header

       new.hdr
              Path to output header to be created

RESULT

       [struct   stat="OK",   fwdxerr=fwdxerr,  fwdyerr=fwdyerr,  fwditer=iter,  revxerr=revxerr,
       revyerr=revyerr, reviter=reviter]

       where fwdxerr and fwdyerr are the maximum errors along each  axis  found  when  projecting
       from  the  original  image  to  the  distorted header; revxerr and revyerr are the maximum
       errors along each axis found when  projecting  from  the  distorted  header  back  to  the
       original  header;  and  fwditer  and reviter are the number of iterations required in each
       direction to converge on a solution.

MESSAGES

       OK     [struct stat="OK", fwdxerr=fwdxerr, fwdyerr=fwdyerr, fwditer=iter, revxerr=revxerr,
              revyerr=revyerr, reviter=reviter]

       ERROR  -i (iterations) argument

       ERROR  -o (order) argument

       ERROR  -t (tolerance) argument

       ERROR  Cannot open status file: statusfile

       ERROR  Cannot open output template file new.hdr

       ERROR  All points offscale in forward transform

       ERROR  All points offscale in reverse transform

       ERROR  Bad template: orig.hdr

       ERROR  Output wcsinit() failed.

       ERROR  Singular Matrix-1

       ERROR  Singular Matrix-2

       ERROR  Allocation failure in ivector()

EXAMPLES

       $ mTANHdr input/SIN_1.hdr alternate.hdr
              [struct    stat="OK",    fwdxerr=4.31068e-05,    fwdyerr=4.42599e-05,    fwditer=4,
              revxerr=1.22123e-05, revyerr=1.19694e-05, reviter=4]

       The output header is a FITS header template containing a TAN  projection  with  polynomial
       focal plane distortions: alternate.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.