%%
% Contour plot of the number of tracks per unit area in the whole event
% set. Units are number per year per one degree latitude square. Each track
% is counted only once in each lat-long box (whose resolution may be set in
% _params.m_ ), unless the track leaves the box and later re-enters it, in
% which case it is counted twice. (By extension, it is counted _n+1_ times if
% it re-enters the box _n_ times after its first encounter.)
%
% This routine uses MATLAB's mapping toolbox. Some of the properties of the
% map can be set in the _params.m_ file.