\HeaderA{gcp}{GREAT-CIRCLE-PATH PARAMETERS}{gcp}
\begin{Description}\relax
Calculates the azimuth and back azimuth of the great-circle-path
between two points (source and receiver) on a sphere.
\end{Description}
\begin{Usage}
\begin{verbatim}
gcp(s, e)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{s}] receiver, or station. This is a list with elements \code{lat}
and \code{lon} given in degrees.

\item[\code{e}] epicenter, or source. This is a list with elements \code{lat}
and \code{lon} given in degrees.

\end{ldescription}
\end{Arguments}
\begin{Value}
a list containing the following elements:
\begin{ldescription}
\item[\code{C}] azimuth, in degrees.
\item[\code{B}] back azimuth, in degrees.
\item[\code{a}] arc distance, in degrees.
\item[\code{lat}] latitude defining the path.
\item[\code{lon}] longitude defining the path.
\end{ldescription}
\end{Value}
\begin{Author}\relax
Eric M. Thompson \textless{}eric.thompson@tufts.edu\textgreater{}
\end{Author}
\begin{References}\relax
Lay, T. and T. C. Wallace, (1995) \emph{Modern Global Seismology},
International geophysics series; v. 58, San Diego: Academic Press.
\end{References}

