A multifunction display (MFD) combines the chartplotter with the screens for the sonar, radar, autopilot and engine data. In this video I finish installing a Raymarine Axiom Pro, which gives GPS navigation using Navionics charts and side-scan sonar.

The MFD connects to the rest of the boat's electronics over the NMEA 2000 network. A smaller boat may only need a simpler combined GPS and sounder, and a computer running free charting software is another option.