windsupport: Compute wind support and drift from a wind and ground speed...

In Rafnuss/GeoPressureR: Global Positioning by Atmospheric Pressure

Compute wind support and drift from a wind and ground speed vectors

Description

Wind support, or wind profit, is the projection of the wind vector \vec{v}_w onto the groundspeed vector \vec{v}_g,

\text{Wind Support} = \frac{\vec{v}_g \cdot \vec{v}_w}{|\vec{v}_g|}

, with \cdot being the cross product.

A positive value indicates that wind was blowing in the direction of movement, while a negative one indicates a head wind.

windspeed and groundspeed should be expressed as complex value where the real part corresponds to the east-west component and imaginary part to the north-south component.

Alternatively to wind support, you can compute the drift (or crosswind component) value with drift = TRUE,

\text{Drift} = \frac{|\vec{v}_g \times \vec{v}_w|}{|\vec{v}_g|}

, with \times being the cross product.

A positive value of drift indicates that the wind is pushing the bird to the right of its intended path, while a negative indicates that the wind is pushing the bird to the left.

You can use abs() (or Mod()) to compute the norm (or absolute value) of the speed vector and speed_to_bearing() to compute the bearing/orientation of the speed vector. The latter computes the trigonometric angle of the speed vector with Arg() and convert this angle to a bearing (North = 0° instead of 90°).

Usage

windsupport(windspeed, groundspeed, drift = FALSE)

Arguments

windspeed	windspeed as complex value
groundspeed	groundspeed as complex value
drift	return drift instead of windsupport

Value

wind support as scalar value (same unit as gs and ws)

Rafnuss/GeoPressureR documentation built on April 17, 2025, 12:58 p.m.