\section{Pre-amble}

%\textbf{This document is under construction; it is partly based on the older documentation of \mapping{}.}

\imager\ is an interferometric imaging package, tailored for usage
  simplicity and efficiency for multi-spectral data sets.

\noindent\textbf{for new users}

\imager{} is build on the \gildas{} infrastructure, namely its command
line interpreter \sic{} and its graphics package \greg{}. Please refer
to their respective documentations for details on the Gildas web site
(https://www.iram.fr/IRAMFR/GILDAS/).

\noindent\textbf{for previous users of \mapping}

\imager\  is \textbf{*** NOT ***} \mapping

\imager{} was created because the initial infrastructure for imaging
in the \mapping{}\footnote{The \mapping{} tool was developped by
S.Guilloteau and J.Pety (IRAM) within the \gildas{} framework.}
program was not adapted to the implementation
of imaging methods that became possible and/or were required for
\NOEMA{} (and useable for \ALMA{}), such as self-calibration,
wide band imaging, or routine processing of Mosaics and Short spacings.
 
\vspace{0.3cm}
\noindent The \imager{} design takes great care of efficiency, by using parallel 
programming and minimizing Input/Output on files. This lead to a 
concept with a single \com{READ} of data, a few (in general only 2) 
simple processing commands with built-in intelligent parameter guesses, 
a visual user control, and a single \com{WRITE} of the results once the 
user is satisfied of it.

\imager{} was initially derived from  \mapping{} by S.\,Guilloteau, and subsequently
extended with many new functionalities. 

T.\,Jacq and
E.\,di\,Folco made numerous suggestions about the user interface, 
and helped testing and documenting the program. 

Although many basic algorithms from \mapping{} were re-used, a large 
number of improvements (in particular for
speed using parallel programming) (and some bug corrections) were performed.
New methods were also developped, tested and implemented.

We took the opportunity to revise and streamline the user interface,
providing access to all tools through simple commands. A special
effort was put on the visualization tools, that provide enhanced
speed and capabilities, yet preserving a very high level of compatibility
with those previously offered in \mapping{}.

