Maretron's GPS receivers stopped outputting compass Variation data on 12/31/2009 when the existing World Magnetic Model ran out. It may cause issues with True Heading, Ground Wind, and other calculations. Firmware 2.2 updates the GPSs to WMM2010. More detail here:
https://www.panbo.com/archives/2010/02/a_world_magnetic_model_reminder_courtesy_maretron.html
How the heck do you update the firmware of a GPS antenna without sending it back to the factory. I have a Maretron GPS N2K that I had to send back last year to fix a failure. When did they begin shipping with the update?
Any word on whether other manufacturers may have this problem?
You can do the update right on your boat's NMEA 2000 network, if you have a Windows PC attached via a Maretron USB100 gateway. It takes just few minutes to download the latest version of N2KAnalyzer and flash the update. Some marine electronics installers have PCs and gateways just for this purpose.