NMEA DBT datagram
The NMEA DBT datagram provides the current depth under the transducer. In new designs, this datagram is frequently used to replace the DBK and DBS datagrams.
Format
$--DBT,x.x,f,y.y,M,z.z,F*hh<CR><LF>
Description
All depths are measured from below the transducer face.
1 $—Talker identifier
2 DBTDatagram identifier
3 x.x,fDepth in feet
4 y.y,MDepth in metres
5 z.z,FDepth in fathoms
6 *hhChecksum
Tip
If you need the depth below the keel, use the NMEA DBK datagram. If you need the depth below the surface, use the NMEA DBS datagram.