
\paragraph{Example (i)}

Observe an OTF map with first OTF subscan from offsets $-300$ $-300$
  to $+300$ $-300$, and  off-source reference
  at $-600$ $-700$, all in system radio projection:
\begin{verbatim}
OTFMAP -300 -300 300 -300 /REFERENCE -600 -700 projection /SYSTEM projection
\end{verbatim}

\paragraph{Example (ii)}

Observe an OTF map with first OTF subscan from offsets $-300$ $-300$
  to $+300$ $-300$, in system trueHorizon (and no off-source reference)
  This is typical for bolometer OTF maps:
\begin{verbatim}
OTFMAP -300 -300 300 -300 /REFERENCE no /SYSTEM trueHorizon
\end{verbatim}



\notes. Visiting observers have also used ONOFF in trueHorizon
combined with OFFSETS ... /SYSTEM projection with \total,
apparently with success.

\notes.

\begin{itemize}

\item one should not specify offsets for the same system with the 
   observing mode and OFFSETS (and there is not need to do this!).

\begin{itemize}
\item
   If the observing mode uses \command{/SYSTEM projection},        \newline
   \command{OFFSETS ... /SYSTEM projection} is ignored (not used).
\item
   If the observing mode uses \command{/SYSTEM trueHorizon},       \newline
   \command{OFFSETS ... /SYSTEM trueHorizon} is ignored (not used).
\end{itemize}

\item in the commands for the observing modes, the offsets for 
   off-source reference positions must be in the same system
   as those of the on-source or OTF positions,
   i.e., /REFERENCE ... and /SYSTEM must select the same system
   (normally, PROJECTION).

\end{itemize}

Details at a technical level about these and more offsets can
be found in the documentation of ``NCS Antennna Mount Drive'' by
Alain Perrigouard.
            