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47_processor_Regatta_um_UK_40
8.3 Calibrating the compass
Please refer to the calibration section in the sensor’s manual.
8.4 Roll and pitch calibration
The calibration of these parameters can be achieved using a digital or laser level. Place
the level on the reference surface indicated by the architect. The 3D Sensor or Compass
Regatta must be free from any heavy metal presence such as a pontoon or a cargo ship
within a 20 meters radius. The boat must be well balanced. Check that the weight
distribution is normal on board. Ideally, the boat should be empty of all sails, anchors,
safety equipment, food, etc… Run this operation in calm water.
The calibration values will be typed in the following Multigraphic or Multidisplay menu:
Menu
►
Sensors
►
Heel angle
►
Offset
Menu
►
Sensors
►
Trim angle
►
Offset
8.5 Calibrating boat speed
Boat speed is measured in the boundary layer which varies from one boat to another.
Paddlewheel sensors measure boat speed inside a disrupted and accelerated water flow.
The measurement is not linear and the resulting error may vary against the heel angle.
The water speed measurement by ultrasonic speed sensors is about ten centimetres away
from the hull. The water flow is much less disrupted and the measure is linear.
Nevertheless, these measurements tend to be 1 or 2% optimistic when the boat is strongly
heeling. This is due to the growth of the boundary limit and the calibration being made with
the boat not heeling.
Calibration can be done in two different ways:
Consecutive runs on a given course:
With this method you need to choose a course with known distance, for example between
two buoys. Reset the log at the starting point, and motor between the two points. Note the
log once reaching the second point. Repeat the run in the opposite way, and note again
the log’s value.
Example:
Run 1: measured log 1,05
Run 2: measured log 1,09
The true distance between the two buoys is 0.97 miles.
Run 1:
92
.
0
05
.
1
97
.
0
=
Run 2:
88
.
0
09
.
1
97
.
0
=
