windSupport: Calculate wind support or crosswind

In mpio-be/windR: Analysis of tracking data in relation to wind

Description

This function calculates the wind support based on the ground direction and speed (e.g. of an animal track) and the wind direction and speed. The wind support can be positive (tailwinds) or negative (headwinds). Logical wind speed and ground speed should be in the same unit (e.g. m/s)

Usage

windSupport(g_direction, g_speed, w_direction, w_speed, crosswind = FALSE)

Arguments

g_direction	The bearing (Can be calculated based on two points using the function bearing)
g_speed	The ground speed (Can be calculated as distance (between two points) / time (between two points))
w_direction	Can be calculated from u and v wind component: atan2(u, v)
w_speed	Can be calculated from u and v wind component: sqrt(u^2 + v^2)
crosswind	If TRUE the function returns the cross wind instead of the wind support

Value

Wind support or cross wind

Examples

# Example 1
windSupport(g_direction = 0, g_speed = 15, w_direction = 1, w_speed = 5)
windSupport(g_direction = 0, g_speed = 15, w_direction = 1, w_speed = 5, crosswind = TRUE)

# Example 2: constant ground direction, different wind direction
d = data.table(w_direction = seq(-pi, pi, pi/24),
               w_speed     = rep(5, 49),
               g_direction = rep(0, 49),
               g_speed     = rep(15, 49) )

               d[, Ws := windSupport(g_direction, g_speed, w_direction, w_speed),
                   by = 1:nrow(d)]
               d[, Wc := windSupport(g_direction, g_speed, w_direction, w_speed,
                   crosswind = TRUE), by = 1:nrow(d)]

               plot(Ws ~ w_direction, d, type = 'l', ylab = 'Ws (black) / Wc (red)',
                         xlab = 'Wind direction')
               lines(Wc ~ w_direction, d, col = 'red')

mpio-be/windR documentation built on Feb. 2, 2020, 10:04 a.m.