NMEA VTG
The NMEA VTG datagram contains the actual course and speed relative to the ground.
NMEA VBW
The NMEA VBW datagram contains water- and ground-referenced vessel speed data.
NMEA VHW
The NMEA VHW datagram contains the compass heading to which the vessel points, and the speed of the vessel relative to the
water.
NMEA CUR
The NMEA CUR datagram contains multi-layer water current data. This includes the depth and speed of the current.