Performance Functions; Calculation Of The Current; True Wind Tables - NKE Multigraphic User Manual & Installation Sheet

2.14 Performance functions

2.14.1 Calculation of the current

The Multigraphic will automatically calculate the current when it is set as a master.
The following channels are created:
Speed of measured current (in knots).
Direction of measured current (in degrees True).
The data can be displayed on the Multigraphic.
Contrary to wind direction, which is measured as the bearing the wind is blowing
from, the current's direction is measured in the direction it is travelling towards. This
value is a True Heading (geographic).
The calculation of the current requires the following channels to be active:
- Magnetic Heading
Magnetic Variation
-
Heading Over Ground
-
- Boat speed
Drift angle
-
The primary sensors must be correctly calibrated to ensure reliable and accurate
information.

2.14.2 True wind tables

The data measured by the wind sensor placed on top of the mast, even when on a
long carbon arm, is affected by the sails.
The wind flow is disturbed around the sails and rig. This is called the "upwash".
This "upwash" affects the measured raw data measured for the calculation of the true
wind direction. Therefore, the true wind direction may be different from one tack to
another and the wind speed varies from upwind to downwind.
The errors due to upwash can be repeated with sail configurations and wind speed
combinations making it possible to apply corrections. A correction table can be filled
for true wind speed and angle.
Warning:
The true wind correction tables only work with the HR or Carbowind sensors
featuring the V2.5 (or newer) firmware.
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