National Marine Electronics Association
Electronic Standards

NMEA 0183

Widely used, but low speed (4.8 Kbps)
Assumes one talker and usually one, but possibly more, listeners
A "talker" only transmits (e.g., GPS)
A "listener" only receives (e.g., basic chartplotter)
A device can be both a talker and listener, such as a chartplotter that listens to GPS and sends directions to the autopilot
Typical devices using NMEA 0183 include
GPS output
Autopilot input and output
Radio device control input (e.g., GPS input) and output (frequency setting)
AIS (standard speed 38.4 Kbps, which works with some but not all NMEA 0183)
Too slow for images like radar
Depending on your particular radar, you may be able to use video for full radar display
Connectors and electronic signal recommended, but not strict standard
Often will interoperate with general-purpose serial interfaces such as RS-232, RS-423, and RS-422
These can be serial ports on a tower/laptop
For laptops, you need NMEA to USB converters

NMEA 2000

Newer standard, considerably faster but still slower than USB and Ethernet
Still on the slow side for sending moving images
Allows multiple simultaneous talkers and listeners
In principle, may be more reliable than Ethernet
Although well-tuned Ethernet works well in critical application\
Ambiguity about connectors and electrical format gone
Implementations are to be independently certified compatible and bear a NMEA seal
Lower electrical power than Ethernet
Unless used to carry 4-8 amps of electrical power to devices
It is possible that a modified Ethernet may still meet the needs. General Motors' original LAN for factory control was obsoleted by Ethernet.
Demonstrated by Furuno USA, JRC, Litton Marine, Navionics, Northstar, Raymarine, Simrad, Teleflex, Trimble, Wood Freeman, and the USCG