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\section{Preliminaries: Pavilion Coordinates}
\label{sec_coords}

The MIT Sailing Pavilion is the center of operations for the Pavlab, or
Marine Autonomy Lab. The \var{(0,0)} coordinates, or datum, is located
at:

\begin{packed_itemize}
\item Latitude  = 42.358456
\item Longitude = -71.087589
\end{packed_itemize}

\vspace{0.1in}
\noindent
These datum coordinates are declared in the top of every \var{.moos} file
in this lab, and set in the plug file \var{plug\_origin\_warp.moos}:

\vspace{0.1in}
\begin{fileverb}
// MIT Sailing Pavilion                                                                   
LatOrigin  = 42.358456
LongOrigin = -71.087589
\end{fileverb}
\vspace{0.1in}

\noindent
All other coordinates are usually configured in local coordinates
relative to the above datum. One convention for choosing a datum is to
choose a point far South and West of any point in the operation area,
to ensure that all local coordinates are positive in sign. Another
convention is to choose a datum location that represents the most
common launching point. That is the case here. In fact, you may notice
in Figure \ref{fig_pavlab_coords} below, the datum is {\em on} the
dock, at the intersection of the Pavilion's wooden dock and the
floating dock section. This is due the datum being set roughly in 2005
when the footprint of the dock was much smaller, only the wooden
portion. The floating portion dock expansion didn't occur until 2012
(resulting in our establishment of the Pavlab in Bay 3 of the
Pavilion), but the traditional datum shown here has persisted.

\vspace{0.1in}
\begin{figure}[H]
  \centering 
  \includegraphics[width=0.82\textwidth]{figs_common/pavlab_coords.png}
  \caption{Useful coordinates related to this lab. Note there are two
    playing field rectangles, a large one (\var{"pav90"}) roughly the
    extent of the docks, and a smaller region (\var{"pav60"}) closer to
    the Pavlab doors on the East end of the dock.}
  \label{fig_pavlab_coords}
\end{figure}
\vspace{0.1in}

\noindent
Note there are two rectangles representing a small and large operation
area. We will use the smaller area during initial testing. The
rectangular area is used by the \app{gen\_swimmers} app to generate
the random swimmer locations.  The two rectangles can be passed by
coordinates to \app{gen\_swimmers}, but an alias for each is also
supported.

\vspace{0.1in}
\noindent
For the small region:

\vspace{0.1in}
\begin{consoleverb}
$ gen_swimmers = --poly=60,10:-30.3602,-32.8374:-4.6578,-87.0535:85.7024,-44.2161 --swimmers=15
$ gen_swimmers = --pav60 --swimmers=15                          (same result)
\end{consoleverb}
\vspace{0.1in}


\vspace{0.1in}
\noindent
For the big region:

\vspace{0.1in}
\begin{consoleverb}
$ gen_swimmers = --poly=60,10:-75.5402,-54.2561:-36.9866,-135.58:98.5536,-71.3241 --swimmers=15
$ gen_swimmers = --pav90 --swimmers=15                            (same result)
\end{consoleverb}
\vspace{0.1in}

\vspace{0.1in}
\noindent
Likewise, in the new baseline mission discussed later in this document,
a new set of random swimmer locations can be generated at launch time
with either of the two MIT regions:

\vspace{0.1in}
\begin{consoleverb}
$ ./launch.sh --pav60  10
$ ./launch.sh --pav90  10
\end{consoleverb}
\vspace{0.1in}


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