Skipper GDS102 - Draught and Offset

Page 30 of 77
SKIPPER Electronics AS
Edition: 2017-06-12
GDS102 Operation and Installation Manual
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Chapter: 2 Operation
Draught and Oset
Draught may be compensated to allow real depth from surface to be shown on the screen and printout.
Draught will always be the distance to the lowest point on the vessel (near the transducer). If the
transducer is not at the lowest point, an oset can be added to compensate for this. This oset is added
such that the depth from keel and depth from transducer can also be given out correctly in the NMEA
formats. The screen will prioritize surface depth, then keel depth and then transducer depth, based
on which parameters are non zero. If two channels are in use, the draught and oset values should
be adjusted for each channel individually. Draught compensation is indicated on top of the screen by
a number and a text (DRFT) to alert the operator to the fact that the shown depth value is adjusted.
Draught is used to correct the Depth Below Transducer (DBT) to Depth Below Keel (DBK) or to Depth
Below Surface (DBS). This is used when the transducer is not at same position as the lower part of the
keel/bottom or if ship want to know the real water depth from surface. Dependant on draught/oset
settings, the text (DBT, DBS or DBK) is also displayed. Draught may be compensated to allow real
depth from surface to be shown on the screen, the printout and in all the NMEA relevant formats.
Draught/Oset settings Top screen indication
Draught = 0 (Default) DBT
Draught > 0 DBS
Oset < 0 DBK
200 kHz
transducer Ch1
50 kHz
transducer Ch2
Sea line
Sea bottom
DBS:
Depth
Below
Surface
DBT:
Depth
Below
Trans-
ducer
DBT
:
Depth
Below
Trans-
ducer
DBK:
Depth
Below
Keel
Draught
value Ch2
Keel
Offset
Draught
value Ch1
Draught: 0.00 m to 99.9 m
Offset: -99.99 to 0.00 m
Draught = 0 m: DBT
Draught > 0 m: DBS
Offset < 0 m: DBK
Draught and offset GDS102
The system can send NMEA for DBS, DBT and DBK at the same time.
Draught:
Vertical distance between a ship's
waterline and the lowest point of
its keel at the transducer.
Offset:
Vertical distance between a ship's
keel and transducer at the
transducer.
DBS:
Depth
Below
Surface
DBK:
Depth
Below
Keel
Offset
Note:
DBS, DBT and DBK messages to external eqipment are
from Primary channel (Default Ch 2).