traipse (version 0.3.0)

track_bearing_to: Track bearing to location/s

Description

Calculate geodesic bearing to a location or locations based on longitude, latitude (from) input vectors and longitude, latitude (to) input vectors. The unit of bearing is degrees. The to values may be a single value or individual to each from location.

Usage

track_bearing_to(x, y, to_x, to_y)

Value

a numeric vector of absolute bearing-to in degrees, see Details

Arguments

x

longitude

y

latitude

to_x

longitude vector of to location/s

to_y

latitude vector of to locations/s

Details

No missing values are required as padding, but input data with NAs will incur an NA in the output.

To use this on multiple track ids, use a grouped data frame with tidyverse code like data %>% group_by(id) %>% mutate(bearing_to = track_bearing_to(lon, lat, to_lon, to_lat)).

Absolute bearing is relative to North (0), and proceeds clockwise positive and anti-clockwise negative N = 0, E = 90, S = +/-180, W = -90.

There is no NA padding in the output value (though missing values in the input will be mirrored in the output).

Examples

track_bearing_to(trips0$x, trips0$y, to_x = 147, to_y = -42)[1:10]
# N E S W
track_bearing_to(0,0, c(0, 10, 0, -10), c(5, 0, -5, 0))

# maximum and minimum value are the same direction (due south)
track_bearing(c(0, -0.00001), c(0, -1))
track_bearing(c(0,  0.00001), c(0, -1))

# the absolute minimum is north
track_bearing(c(0, 0), c(0, 1))