Garmin GPSMAP 168 Sounder - Manual (Page 54)

43
Reference
Sonar Tab Options
• Scale— controls the depth ‘Scale’ displayed vertically along the right side of the chart. The
depth ‘Scale’ can be confi gured to display four different ways: as an ‘Overlay’, in the ‘Corners’,
with ‘Basic’ or ‘No Scale’.
• Noise Reject— helps fi lter unwanted noise from the chart. The ‘Noise Reject’ tool can be
turned ‘Off’, set to ‘Auto’ (automatically adjusts for optimum viewing) or to a fi xed ‘Low’,
‘Medium’ or ‘High’ setting.
When setting the Noise Reject tool: the HIGHER the noise rejection setting, the unit is
more likely to NOT show fi sh or structure.
• Keel Offset— allows the user to offset the surface reading for the depth of a keel. This makes
it possible to measure depth from the bottom of your keel instead of from the transducer’s
location. Enter a positive number to offset for a keel. It is also possible to enter a negative
number to compensate for a large vessel that may draw several feet of water. The ‘Keel Offset’
will be refl ected in the depth reading.
• Water Type— since sound waves travel through ‘Fresh’ and ‘Salt’ water at different rates it is
necessary to select the ‘Water Type’ to ensure accurate readings on the unit.
• Remember— the unit can be set to remember ‘All’ of the Sonar settings including the
Adjustment Bar (even after it has been powered off and back on), or just the ‘Setup Only’
items on the Sonar tab.
• Calibrate Water Speed— this is only available if you are using a speed-capable transducer.
Calibration is required to ensure that the Water Speed displayed on your unit will be accurate.
The unit will automatically use the GPS ground speed, if it is available, for comparison on
the calibration. If a GPS ground speed is not available, use either your boat’s speedometer
reading (not always accurate) or a stopwatch to determine your speed over a certain distance
(distance / time = speed). It is recommended that the calibration take place in water having
little or no current.
)
Calibrating the Speed Sensor
Transducer at Surface
Enter (+) positive
number to show depth
from bottom of keel
Transducer at Bottom of Keel
Enter (-) negative number to show
depth from surface
168 Manual Part 1.indd 43 11/18/2002, 3:36:38 PM