I am trying to use the gt-31 as a gps-device for my laptop. Connected by USB the connection seems ok. GPS-fox doesn't work and in MS Autoroute I get the message "The GPS receiver is sending messages, but they are not being recognised as NMEA 2.0 compatible. Make sure the input/output format is set to deliver NMEA 2.0 compatible messages at the correct baud (4800 bps)." The output on the GT-31 is (of course) set to NMEA. In the configuration of the driver (Prolific USB-to-Serial Comm Port) the baudrate is standard 9600, but can manually be set to 4800. Still doesn't work. I run Vista.
Any clue anyone?
Not sure if this will work for you but try setting the baudrate to 38400, 8, n, 1.
I have a BGT-11 and use Bluetooth to conect to my PDA with the above settings.
Still the same. Thanks for the suggestion. Still think that it should work though...

The settings work for GPS-fox under windows XP. I'll install MS Autoroute tomorrow, maybe it´s just another vista-problem.
Now GPS-fox is also running under vista. Seems to be a baudrate problem. MS Autoroute (2007) expects 4800 baud, the GT-31 will not go that low. 38400 works fine with gps-fox.
Thanks for the help.
Problem solved!

Stumbled across a little program called "GpsGate" ( This program allows you to share one gps among several applications and can also make "translations". With the BG-31 I can use Garmin NRoute, wich normally only works with garmin gps devices. I can also "translate" the baudrate from 38400 to (the standard NMEA) 4800. This is  €10,- well spent.

It has a lot more of interesting feature (sharing gps over the internet), so have a look.