Metview Macro Library function. Used to plot a straight line onto a non-cylindrical map projection. Internally, the line is split into a number of segments and the returned result is an Input Visualiser object which can be passed to the plot()
command along with an optional Graph Plotting object.
definition mvl_geoline(lat1 : number, lon1 : number, lat2 : number, lon2 : number, incrm : number)
The first four parameters define the end-points of the line. Parameter incrm
specifies the increment, in degrees, into which the line should be split.