unction [ ] = plotsat(plotMat,gpsWeek,elMaskRad)
% plotsat : Plot the calculated satellite positions or trajectories on an
%       elevation-azimuth plot.
%
%
% INPUTS
%
% plotMat ----- N-by-4 matrix arranged as follows:
%
%             [svID gpsSec elRad azRad;
%             svID gpsSec elRad azRad;
% ...
%             svID gpsSec elRad azRad]
%
%             svId is the SV identification number, gpsSec is GPS time in
%             seconds of week, elRad and azRad are the SVs elevation and
%             azimuth angles, in radians.
%
%
%             For positional plot make all gpsSec entries identical. For
%             trajectory plot, format plotMat in batches with equivalent
%             number of SVs, each batch having a constant gpsSec.
%
% gpsWeek ----- GPS week number corresponding to the first row in plotMat.
%
% elMaskRad --- Elevation mask angle, in radians.
%
%+------------------------------------------------------------------------------+
% References:
%
%
% Author: Todd Humphreys and an anonymous Cornell graduate student
%+==============================================================================+

% define physical constants
navConstants;

% find out from 'plotMat' if plotting satellite locations or trajectories in
% addition determine how many satellites are being tracked and how many
% samples for each satellite (# samples / satellite must always be equal)
gpsTime = plotMat(1,2);
i = 1;
t = gpsTime;
while ((i ~= size(plotMat,1)) & (t == gpsTime))
i = i + 1;
t = plotMat(i,2);
end
if (t == gpsTime)
sats = i;
else

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