A casual glance at documentation I can find on installing Outback systems indicates they are using some kind of canbus networking. So I doubt plain NMEA input will work there. I thought I had read somewhere once about Outback being able to use normal NMEA, but maybe I was wrong.
Most agricultural systems use a protocol called j1939 on top of the physical Canbus layer and so far as I know it's not yet encrypted. That can be analyzed. I was not able to find much in the way of Linux support for j1939. But I wonder if you could get Linux's built-in canbus networking support to talk to the machine's bus, whether you could use wireshark to view and filter those messages.
I fully expect certain brands to encrypt their communications buses down the road. Or at least involve cryptographic handshaking. Are you an "authorized" GPS receiver? If not, no go. We've seen this kind of rubbish in consumer market for years now (HDCP, DRM). Just recently it was announced USB C will soon authenticate chargers. It's for safety they say. You can bet the only "safe" charger for an iPhone will be an Apple one before it's all finished. Sorry for the off-topic rant!
Last edited by torriem; 01-19-2019 at 02:05 PM.