The visir_util_detect_shift recipe
===============================================================

.. data:: visir_util_detect_shift

Synopsis
--------

2012

Description
-----------

Detects beams in a background subtracted multi-beam image, determines the shifts between different images and their correlation. Images can be rejected if their correlation is bad.

The files listed in the Set Of Frames (sof-file) must be tagged: 
VISIR-chopnod-corrected-file.fits BKG_CORRECTED
bad-pixel-mask.fits STATIC_MASK
The output consists of single beam images of the size of the throw. The shifts will be written int CRPIX[12].


Constructor
-----------

.. method:: cpl.Recipe("visir_util_detect_shift")
   :noindex:

   Create an object for the recipe visir_util_detect_shift.

::

   import cpl
   visir_util_detect_shift = cpl.Recipe("visir_util_detect_shift")

Parameters
----------

.. py:attribute:: visir_util_detect_shift.param.template

    Correlation template used to detect shifts and reject bad images.  If  none given an averaged image is used (str; default: 'NONE') [default="NONE"].
.. py:attribute:: visir_util_detect_shift.param.min_correlation

    Minimal correlation to the template required to be accepted (float;  default: 0.5) [default=0.5].
.. py:attribute:: visir_util_detect_shift.param.max_shift

    Maximal allowed object shift for an image to be accepted (float;  default: 10.0) [default=10.0].
.. py:attribute:: visir_util_detect_shift.param.max_mad

    Maximal allowed median absolute deviation for an image to be accepted.  <= 0 equals no limit (float; default: 0.0) [default=0.0].
.. py:attribute:: visir_util_detect_shift.param.naverage

    Number of planes to average before attempting to detect the shifts.  (long; default: 1) [default=1].
.. py:attribute:: visir_util_detect_shift.param.method

    Method to determine beam shifts.  xcorrelate: use the cross  correlation shift.  brightest: use the position of the brightest pixel  (str; default: 'xcorrelate') [default="xcorrelate"].
.. py:attribute:: visir_util_detect_shift.param.no_shift

    Sets whether to apply the determined shifts in following recipes. Set  to TRUE of shifts appear too large. (bool; default: False) [default=False].
.. py:attribute:: visir_util_detect_shift.param.no_reject

    If true images with bad statistics will not be rejected and no shift  correction is done (bool; default: True) [default=True].
.. py:attribute:: visir_util_detect_shift.param.beampos

    Define the positions of the beams. These positions are cut by the  window to extract the single beam images.  Format:  sign:x,y,window;sign:x,y,window;...   where sign is "pos" or "neg"  depending on whether the beam is positive or negative.  The window is  optional and defines the size of the cut image around the beam. The  default window is the chop throw.  E.g.: pos:50,60;neg:50,160;  By  default autodetection is attempted.  (str; default: 'NONE') [default="NONE"].
.. py:attribute:: visir_util_detect_shift.param.eccmax

    The maximum eccentricity allowed in the combination of the three (in  parallel nod/chopping) or four (in perpendicular nod/chopping) beams.  In parallel mode, three perfectly aligned points spaced with the  chopnod throw will have eccentricity 0, while in perpedicular mode a  square with the chopnod throw as the side length will have  eccentricity 0 (float; default: 0.25) [default=0.25].


The following code snippet shows the default settings for the available 
parameters.

::

   import cpl
   visir_util_detect_shift = cpl.Recipe("visir_util_detect_shift")

   visir_util_detect_shift.param.template = "NONE"
   visir_util_detect_shift.param.min_correlation = 0.5
   visir_util_detect_shift.param.max_shift = 10.0
   visir_util_detect_shift.param.max_mad = 0.0
   visir_util_detect_shift.param.naverage = 1
   visir_util_detect_shift.param.method = "xcorrelate"
   visir_util_detect_shift.param.no_shift = False
   visir_util_detect_shift.param.no_reject = True
   visir_util_detect_shift.param.beampos = "NONE"
   visir_util_detect_shift.param.eccmax = 0.25


You may also set or overwrite some or all parameters by the recipe 
parameter `param`, as shown in the following example:

::

   import cpl
   visir_util_detect_shift = cpl.Recipe("visir_util_detect_shift")
   [...]
   res = visir_util_detect_shift( ..., param = {"template":"NONE", "min_correlation":0.5})


.. seealso:: `cpl.Recipe <http://packages.python.org/python-cpl/recipe.html>`_
   for more information about the recipe object.

Bug reports
-----------

Please report any problems to `Find beam positions and reject bad images <Julian Tayor>`_. Alternatively, you may 
send a report to the `ESO User Support Department <usd-help@eso.org>`_.

Copyright
---------

This file is part of the VISIR Instrument Pipeline
Copyright (C) llundin@eso.org European Southern Observatory

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, 
MA  02111-1307  USA

.. codeauthor:: Find beam positions and reject bad images <Julian Tayor>
