Weather Instrument

Connection, configuration, and operational features of an anemometer or ship weather station.

Menu path
→ → Sensors → Add Sensor → Weather

Weather Instrument Purpose

When an anemometer is connected, ECDIS displays wind characteristics according to the navigator’s needs.

Note

An anemometer (wind sensor) is a navigational instrument for measuring wind speed and direction.

A Wind tab is displayed in the multi-function window.

Wind data is displayed in the Navigational Panel.

Warning

Depending on the connected navigational sensors and the type of anemometer, some wind types (true, apparent, relative) may be unavailable.

Weather Instrument Configuration

The sensor connection and setup are performed in accordance with the procedure.

Ensure that in the receiver settings:

Processing of received messages is correctly configured
Header processing is enabled
Checksum verification is configured

The anemometer transmits sentences with the following header:

WI — Weather Instrument

Recommended Sentences

Wind Sentences

Depending on the type of transmitted sentence, the wind sensor can generate the following wind types:

$--MWD — True or magnetic wind direction, wind speed
$--MVW — Relative wind direction and speed, Calculated wind direction and speed

For details on wind direction recalculation.

Weather Instrument Operational Features

Wind data is displayed in the Navigational Panel.

No.	Element
1	Parameter name
2	Sensor name
3	Wind direction (depends on the selected wind type)
4	Wind speed (depends on the selected wind type)
5	Wind type selected in the Wind tab of the multi-function window
6	Wind speed units, set in Measurement Units (m/s, knots, km/h)

In the Wind tab, the selected wind direction relative to the vessel is displayed graphically.

No.	Element	Description
1	Wind type selection
2	Wind speed	Wind speed of the selected type
3	Wind direction	Wind direction of the selected type
4	Wind force	Wind force in Beaufort scale points
5	Vessel symbol	Orientation always vertical
6	Compass meridian	From gyrocompass — true, from magnetic compass — magnetic
7	North direction	Compass north direction (true or magnetic, depending on the heading source)
8	Wind vector	Wind vector of the selected type

Wind Types

ECDIS displays three wind types:

True Wind — wind relative to the water surface. Determined by the anemometer taking into account the vessel’s heading and speed, or received directly from the sensor if it is installed on a stationary platform.
Relative/Apparent Wind — wind perceived by an observer on a moving vessel. It is the vector sum of the true wind and the opposing flow from the vessel’s motion.
Calculated Wind — wind calculated by ECDIS based on anemometer data, heading, and vessel speed. Used when the sensor does not provide direct true wind values.

Wind Direction Recalculation

Depending on the type of received sentence, ECDIS recalculates wind directions for the navigator’s convenience:

$--MWD — True (broadcast), Relative, Calculated.
$--MWV:
- Relative: Relative (broadcast) and Calculated
- Calculated: Calculated (broadcast)

Wind Direction Calculation Formulas

Wind direction calculation is performed using the following formulas:

$V_{tw} = \sqrt{{STW}^{2} + V_{aw}^{2} - 2STWV_{aw}\cos\left( K_{aw} \right)}$

$K_{tw} = HDG + K_{aw} \pm KK$

$KK = arccos\left\lbrack \frac{\left( V_{aw} - STW\cos(K_{aw}) \right)}{V_{tw}} \right\rbrack$

Where:

$STW$ — vessel speed, kn.
$HDG$ — vessel heading
$V_{aw}$ — apparent wind speed, kn.
$K_{aw}$ — apparent wind direction, °. If the sensor provides values relative to the vessel’s centerline, conversion to the circular geographic system is required:

$K_{geo} = HDG + K_{rel}$ (at 0° ≤ $K_{rel}$ ≤ 180°)

or

$K_{geo} = HDG - K_{rel}$ (at 180° < $K_{rel}$ < 360°)
$V_{tw}$ — true wind speed, kn.
$K_{tw}$ — true wind direction
$KT$ — calculated wind direction
$VT$ — calculated wind speed
$KK$ — angle between true and apparent wind

Important

Wind parameter calculation is performed when heading and vessel speed data from sensors are available. If heading and speed data are lost, wind value recalculation will be suspended.

Examples of wind data display with various sensor state combinations:

Alarm and warning zone

Navigational Panel

Wind tab