I had a revelation about a month ago. I always have the laptop with us when cruising, or traveling, for e-mail, games, and a full collection of charts.( regular raster Maptech charts). Did the same thing Oldgrowth did.... The revelation was that I could order the Gps engine antenna from maptech for $100, plug right into the UBS port and it now gives me a large chart plotter on my laptop. With live positioning using Maptech 'Offshore Pro". On the road I use mapsourse road info from Garmin, and when I get home I open the topo maps with Terrain Navigator by Maptech for Montana. It gives me large scale live tracking and positioning on all three programs. Could have been doing that a couple years ago if I had known. All info is transferable to the M-4 Garmin with Maptech software. Garmin will not tell anyone how these programs work together, but Maptech will.
That $100 was the best investment of all.
Captd