Calibrate Speed - NorthStar NS3100 Multi Instrument Reference Manual

3-7 Calibrate speed

Measured speed
Distance travelled
10
Calibration may be required, because different hull
shapes have different water flow characteristics.
Speed calibration can be done either by the speed or
by the log, as described below. If speed readings are
taken from a GPS receiver (see section 8-1), then you
can not calibrate it.
Calibrate by speed
In this method, travel at a measured, constant speed.
Use the speed displayed on a GPS receiver, follow
another boat travelling at a known speed or make a
timed run over a known distance.
Note that for accurate calibration:
The speed from a GPS receiver should be above 5
knots.
The speed from another paddlewheel transducer
e.g. another boat - should be between 5 and 20
knots.
Best results are achieved in calm conditions where
there is minimal tidal current (best at high or low
tide).
Continue travelling at this measured, constant speed
and calibrate the speed as follows:
1 Press + several times until the Speed
Calibration screen is displayed (after this, it does
not matter if the boat speed changes).
2 Press or to change the displayed speed to
the measured boat speed.
3 Press .
Calibrate by log
In this method, travel a known distance in a straight
line over a course. Best results are achieved in calm
conditions where there is minimal current (best at
high or low tide). Tidal effects may be reduced by
making the trip twice, parallel to the current, once in
each direction.
1 At the start of the course, reset the trip log (see
section 4-1). Travel in a straight line over the
course, then repeat in the other direction.
2 At the end, note the trip log distance (see section
4).
3 Press + several times until the Log Calibration
screen is displayed.
4 Press or to change the displayed distance
travelled to the actual distance you travelled over
the course.
5 Press .
Northstar NS3100 MULTI