# Definitions

##### TWD

**True Wind Direction**

The direction from which the wind blows, regardless its speed and the attitude of the boat.

By convention, we always refer to the direction the wind blows __ from__, and not where it blows

__to__.

##### TWS

**True Wind Speed**

The speed of the wind, regardless its direction and the attitude of the boat.

Wind speed is generally expressed in Knots, but the game also allows speeds in km/h.

##### HDG

**Heading of the Boat**

The direction which the boat points to. This is what you set by moving the helm, and is the direction your boat will be keeping as long as the 'Locked TWA' game option is not set.

##### Knot

The knot is a unit of speed equal to one Nautical Mile per hour, exactly 1.852 km/h (approx. 1.15078 mph).

The ISO standard symbol for the knot is **kn**; **kt** is also common, and used by Virtual Regatta™ and on this site.

##### Nautical Mile

A Nautical Mile is a unit of measurement defined as exactly 1,852 metres (6,076.1 ft; 1.1508 mi).

Historically, it was defined as one minute of latitude, which is equivalent to one sixtieth of a degree of latitude.

The derived unit of speed is the Knot, defined as one nautical mile per hour.

The ISO standard recognizes several symbols; **NM** is used by Virtual Regatta™ and on this site.

##### TWA

**True Wind Angle**

This is the angle between your HDG and the TWD.

Two handles are displayed on the compass:

- The
**white disc**is the helm, and indicates the boat's Heading (*HDG*). - The
**white triangle**indicates the direction of the wind (*TWD*).

On the example beside, the boat is heading 298°, while the wind is coming from 5°.

If you do the maths, there is an angle of 67° between those two headings, and that is exactly what the **TWA** is.

Additionally, we often indicates is the wind comes from port side (left) or from starboard side (right).

The game interface also provides a 'Locked TWA' option.

When this option is enabled, then the boat will no more sail straight ahead. Instead, it's path will be curved so that it
constantly keeps the same TWA.

##### Boat Speed

The Boat Speed represents the straight speed of the boat in the direction of its heading.

It is generally expressed in Knots, though Virtual Regatta™ also supports speeds in km/h.

In the Attitude Panel, the 'Boat Speed Projection to Axis' option enables the graphical visualization of that speed over the Chart, as shown on the picture beside.

The Boat Speed is the value you read at the intersection of the TWA (blue radius) and the curve, away from the center from a certain distance which represents the amount of speed for that angle.

On the example beside, we can read that the boat would sail at a speed of 9.185 kts if sailing at a TWA of 80° with a Code 0.

##### VMG

**Velocity Made Good**

The VMG represents the amount of the boat speed projected to the wind direction axis.

We often refer to this speed to figure out the best angle by which the boat can sail upwind or downwind.

In the Attitude Panel, the 'VMG Projection to Axis' option enables the graphical visualization of that speed over the Chart, as shown on the picture beside.

From a mathematical point of view, the Best VMG is the point of the curve having an horizontal outter tangent.

On the example beside, we can read that the best upwind VMG is 42°, providing a 6.332 kts toward the wind direction.

The Best VMG is only an indication; you may not have to follow it systematically, because your course might not go strictly in the same direction than the wind's.