7-3-2 True and apparent wind speed and direction

Apparent wind speed and direction are the values measured on the boat. True wind speed and direction are the values after allowing for boat speed through the air.

If the boat is moving, then the apparent wind speed is different to the true wind speed and the apparent wind direction is different to the true wind direction, as shown below.

Boat at rest

True wind speed is the same as apparent wind speed and true wind direction is the same as apparent wind direction

Boat is at rest

Boat moving upwind

Apparent wind speed is greater than true wind speed

and apparent wind direction is closer to dead ahead than true wind direction

 

True

True

Apparent

 

Apparent

True wind

wind

Apparent

wind speed

wind speed

wind

speed

28 kts

direction

28 kts

wind

speed 20

20 kts

 

45º

 

direction

 

kts

 

 

 

 

 

 

30º

 

 

 

 

 

 

Boat

 

Boat

 

 

 

speed

 

speed

 

 

 

10 kts

 

10 kts

 

 

 

Boat moving downwind

Apparent wind speed is less than true wind speed and apparent wind direction is closer to dead ahead than true wind direction

True

 

Apparent wind

wind

True wind

speed 15 kts

speed

 

direction

 

20 kts

 

135º

 

 

 

 

 

Boat

 

 

speed

 

 

10 kts

Boat

 

 

speed

 

 

10 kts

 

 

True

Apparent wind

wind

speed

speed 15 kts

20 kts

 

Apparent wind direction 107º

Reference Manual

37

 

Page 37
Image 37
NorthStar Navigation NS3300 manual True and apparent wind speed and direction, Boat at rest, Boat moving upwind

NS3300 specifications

The NorthStar Navigation NS3300 is a powerful marine navigation system designed for both commercial and recreational vessels. It represents the pinnacle of marine technology, enabling sailors and captains to navigate with precision and confidence, regardless of conditions. The NS3300 is particularly renowned for its user-friendly interface, advanced features, and robust design, making it a favored choice among maritime professionals.

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The NS3300 is equipped with a high-resolution color display that makes information easily readable, even in direct sunlight. The touchscreen interface is intuitive and responsive, allowing for quick access to essential navigation data. Users can customize their screens according to their preferences, displaying the information that matters most to them, including charts, routes, and environmental data.

Another critical aspect of the NS3300 is its advanced chart plotting capabilities. The system supports various digital chart formats, allowing users to integrate their preferred charts seamlessly. The built-in electronic chart display functionality helps in visualizing navigation routes and identifying potential hazards, ensuring safer passage through busy waterways.

The NS3300 also features connectivity options that enhance its functionality. With support for Wi-Fi, Bluetooth, and NMEA 2000 protocols, users can connect the NS3300 to other onboard systems, such as radar, sonar, and autopilot systems. This interoperability allows for a more integrated approach to navigation, providing a comprehensive overview of the vessel's environment.

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