A:  One of the most important innovations in the marine electronics field is the ability of one instrument to “talk” to another through what’s known as the NMEA (National Marine Electronics Association) interface. Most manufacturers’ equipment is built to support this interface, and almost every chart plotter, radar or autopilot is now able to communicate regardless of brand.

The important thing is to make sure both electronic items have NMEA-interface electronics and connecters. If so, it’s clear sailing. Of course, a chart plotter doesn’t have to be interfaced with your autopilot, but it sure adds a new dimension to piloting if it is.
If it’s not interfaced, you’ll have to make occasional manual adjustments to the autohelm’s setting to keep the vessel’s course near your intended line on the plotter. Usually this isn’t a big deal, but drifts associated with sailing or currents can make continual adjustments a chore.

With an NMEA interface setup, the plotter submits correction information to the autopilot continuously and automatically. The autohelm then makes its own corrections and all you have to do is watch for logs! (Note that use of this equipment presents a safety issue. It’s like having an additional crewmember on board to do the steering—but that crewmember is blind to other vessels and hazards.) When properly set up, a good autopilot and chart plotter with NMEA interface will steer your course with uncanny accuracy, probably better than you can.

Hooking up NMEA connections should be covered in the instruction manual for so-equipped electronics. If in doubt, check with a technician.