Using the External Computer Data Link
MicronNav System
0656-SOM-00001-07
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7.2.11. NMEA $GPDBT
This NMEA string format is used for Water Depth data output and is the Depth Below
Transducer value that is mainly sent by positioning devices. It provides the Z (Depth) co-
ordinate output position in the USBL system.
The full string format is as follows:
‘$GPDBT’ Reply Data Structure
Data Description
Data Range
Field Range
NMEA string header
Always ‘$GPDBT’
hhhhhh
Comma separator
Always ‘,’
,
Depth in units of Feet
0 to 999999
f.ff
Comma separator
Always ‘,’
,
Units Identifier
Always 'f'
U
Comma separator
Always ‘,’
,
Depth in units of Metres
0 to 999999
M.MM
Comma separator
Always ‘,’
,
Units Identifier
Always 'M'
U
Comma separator
Always ‘,’
,
Depth in units of Fathoms
0 to 999999
F.FF
Comma separator
Always ‘,’
,
Units Identifier
Always 'F'
U
Delimiter (asterisk)
Always ‘*’
*
Checksum (in Hexadecimal)
(XOR of bytes between, but not inclusive
of, '$' and '*')
00 to FF
cc
(Carriage Line Feed)
N/A
<CR><LF>
Example:
Z (Depth) value = 54.12 metres.
ASCII Output Always = “$GPDBT,177.55,f,54.12,M,29.59,F*32<CR><LF>”
Where; “<CR>” is Carriage Return (ASCII code 13), “<LF>” is Line Feed (ASCII code 10).