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• Speed Calibration - If you are using a transducer equipped to display speed
through water (STW), calibration is required to ensure that the STW displayed by
your GPSMAP 135 Sounder will be accurate. The unit may be calibrated automatically
or manually, but auto calibration is recommended and is the default setting.
To calibrate the unit:
1. Press the
O
key to display the sounder options page.
2. Using the
R
keypad, highlight ‘Sounder Setup?’ and press
T
.
3. Choose between auto and manual calibration.
To use Auto Calibration:
1. Ensure ‘Auto Calibrate?’ is displayed in the speed calibration field. If it is not, press
O
to display the calibration menu.
2. Highlight ‘Auto Calibrate’ and press
T
.
3. Press
T
again and an instruction message will appear.
4. After reading the instructions, and when you are ready to begin the calibration,
press
T
.
5. Slowly accelerate your boat to a maximum safe cruising speed and then back
down to a stop and press
T
.The minimum and maximum speed which the unit
is now calibrated for will be displayed in the ‘calibrated range’ field.
6. Auto calibration is complete.
When manual calibration mode is selected, the speed calibration bar will
appear as a white horizontal strip, with a black slider bar positioned in the
middle.
Before entering the calibration, you will need to compare the value shown on
the speed calibration field’s STW display, with your boat’s actual speed as deter-
mined by the speedometer or by using a stop watch. Accelerate to a safe speed
and compare the two speed readings.
A. Calibration is required to use the GPSMAP 135
Sounder with a transducer equipped for accu-
rate speed through water readings.
B. Follow instructions for auto calibration
carefully.
34
AB
SECTION
3
SOUNDER PAGE
Sounder Setup and
Calibration
GPS 135 Rev C 8/4/98 4:18 PM Page 34