Furuno FA-100 Operator's Manual page 62

APPENDIX
DTM - Datum reference
Local geodetic datum to which a position location is referenced.
$--DTM,ccc,a,x.x,a,x.x,a,x.x,ccc*hh<CR><LF>
| | | | |
| | | | |
| | | | |
| | | | |
| | | | +---+------------- 4
| | +---+------------------- 3
| +------------------------- 2
+---------------------------- 1
1. Local datum W84 - WGS84
W72 - WGS72
S85 - SGS85
P90 - PE90
999 - User defined
IHO datum code
2. Local datum subdivision code
3. Lat offset, min, N/S
4. Lon offset, min, E/W
5. Altitude offset, m (Not used.)
6. Reference dattum W84 - WGS84
W72 - WGS72
S85 - SGS85
P90 - PE90
7. Checksum
AP-12
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| | | +--- 7
| | +------ 6
| +---------- 5