What does SOG stand for, and what does it measure on an NMEA 2000 network?

• A. Speed Over Ground; the vessel speed relative to the earth’s surface.
• B. System Orientation Gauge; heading accuracy.
• C. Signal Output Gain; signal strength of PGN transmissions.
• D. Solar Optical Grid; solar irradiance affecting instruments.

Answer: (A)

Speed Over Ground is what the data field represents: your vessel’s speed relative to the Earth’s surface. On an NMEA 2000 network, SOG is typically derived from GNSS data (like GPS) and gives how fast you’re actually moving over the ground, accounting for currents and wind drift. This is different from speed through the water, which is how fast the hull moves through the water and is measured by a log or paddle wheel. So the best answer is that SOG stands for Speed Over Ground, measuring ground-relative speed.