The output from the EM-406a is in NMEA sentences. Each sentence starts with a ‘$’. There are a bunch of sentences that it can spit out, but only a few that we are interested in. For example sentences look at the EM-406a Manual.
- RMC-Recommended Minimum Specific GNSS Data, message 103,04
- – this has all the basic data that you’d want for a boat; lat, long, speed (in knots)
- VTG-Course Over Ground and Ground Speed, message 103,05
- – this will give us the heading relative to magnetic north. That way we can directly compare the reading from the compass