Receive Coordinates from a GPS Receiver

This very basic example shows how to communicate with a "Think Navi Free" GPS system via an RS-232 serial port.

The example here just reads the output from the GPS system and parses the sentences to extract the coordinates. 
It checks that the sentence is valid but does not verify the checksum. 

This works on Windows XP/7 with a standard serial port and with a Keyspan USB to serial adapter.
It also works on Macintosh OS X and OS 9.

It should work with USB GPS dongles to.

On Windows 10 and later there can be many problems getting the older USB receivers hardware to register drivers.
So newer receivers should be used.
