This code outputs various NMEA strings to a com port. The code was
originally used to test naviation programmes.
First select the required com port and the required NMEA message string.
There is a default starting position but this can be changed to suit just by typing
in a new position.
Click on the Start button the current position displayed will change according
to the speed and heading selected and the selected NMEA string will be output to the com port
and will reflect the current position as displayed.
There is a text box which is normally not visible. If you change this to visible the relevant
NMEA string can be displayed.
