Calibrating The Water Speed - Garmin GPSMAP 495 Owner's Manual

Setting up and Using Sonar > Setting up the Sonar Page

Calibrating the Water Speed

If you select Temp, Spd is for the Transducer option on the Sonar
Setup tab, you also need to calibrate the water speed to ensure that
the Water Speed shown on your unit is accurate. The calibration
should take place in water having little or no current.
The unit automatically uses 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. To find out your speed, divide the distance by the time.
To calibrate the water speed:
1. From the Sonar tab, Setup sub tab, use the ROCKER to highlight
Calibrate Water Speed, and press ENTER.
2. Bring the boat to a cruising speed. Both the top ground and
uncalibrated water speeds are shown at the bottom of the
calibration window. Note your top speed, then stop the boat, and
press ENTER.
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Calibrating the Water Speed
3. By default, the top ground speed is automatically shown. If a
ground speed is not available, the top uncalibrated water speed
is used instead. If the new speed is correct, highlight OK, and
press ENTER.
If you want to manually enter a calibration, press ENTER while
the speed is highlighted, enter a new speed, and press ENTER.
If the boat is not moving fast enough or the speed sensor is not
outputting a speed, "Boat Is Not Moving Fast Enough To Calibrate"
shows at the bottom of the screen. Check that the speed sensor
wheel is moving or safely increase boat speed. If there is a problem
with the speed sensor or if a speed sensor is not installed, "Water
Speed Sensor Is Not Working" appears at the bottom of the screen.
Check connections of speed sensor cables.
GPSMAP 495 Owner's Manual