Any computer wizard/descent helmsman out there in Amel Land able toI am neither a computer whiz nor a decent helmsman but here is a
solution to your problem.
Purchase "The Capn" Navigation Software and the appropriate electronic
charts for your area. Look at the B&G manual and find the 2 wires for
the ground and data. Connect these to a 9 pin female plug that will
attach to your serial port. The wires connect to pins 2 and 5. If
you buy "The Capn" from Steve Bowden at SeaTech Systems
(1-800-444-2581) he will help you with the set up. If your GPS data
goes to the B&G then that will also be available to "The Capn".
This set up allows you not only to see the boat at all timeson the
electronis chart but also to see the digital data of the lat longs,
wind angle, wind speed, speed, SOG, COG, depth and time from the GPS.
However, if you also wish to be able to see the compass heading that
will be more difficult. On SM 248 Amel installed an Autohelm fluxgate
compass. If you wish to get that data you will have to get a Noland
Multiplexer from Blue Water in Florida and feed into it the NMEA
output from the B&G and the NMEA output from the Autohelm CPU. The
multiplexer outputs a RS232 signal which can be attached to the 9 pin
female plug as above.
I hope that this helps
Peter (former owner of SM 248)