Calculate the cross-track intersection between the position of a body (i.e. an aircraft) and a great circle arc as defined by two points (i.e. the runway's thresholds).

## Usage

cross_track_intersection(b, a1, a2)

## Arguments

b

coordinates of the body, b: a vector of longitude, latitude (in decimal degrees) and altitude (in meters) in WGS84

a1

first coordinate of a great circle arc: a vector of longitude, latitude (in decimal degrees) and elevation (in meters) in WGS84

a2

second coordinate of a great circle arc: a vector of longitude, latitude (in decimal degrees) and elevation (in meters) in WGS84

## Value

a WGS84 vector with longitude and latitude (decimal degrees)

## Details

The cross-track intersection between the position of a body, B, (i.e. an aircraft) and a great circle arc as defined by two points, A1 and A2, (i.e. the runway's thresholds) is the intersection, X, of the above arc with the great circle arc passing through the ground projection of B, G, and perpendicular to A1-A2.

Other utilities: along_track_distance(), altitude_azimuth_distance(), cross_track_distance()

## Examples

if (FALSE) {
# aircraft (longitude, latitude, altitude)
b <- c(8.086135, 49.973942, 6401)
# EDDF: 07R (longitude, latitude, altitude)
a1 <- c(8.53417, 50.0275, 328)
# EDDF: 25L
a2 <- c(8.58653, 50.0401, 362)
cross_track_intersection(b, a1, a2)
}