it is not powered from nmea2000... it will have a power
plug, and a nmea 2000
plug.
the nmea 2000 backbone will also need power.
if the unit ever dies, and all your phones and ipads die, and everything else. and you have to resort to using the mag
compass to get somewhere. unbolt the display and put it somewhere else...
if it's close it'll likely move the compass. take a reading before and after install, and with it powered on and off. and you'll see if it changes anything.