# along_track_distance: Compute the along-track distance from a great circle arc In nvctr: The n-vector Approach to Geographical Position Calculations using an Ellipsoidal Model of Earth

## Description

Compute the along-track distances of a body, 'b' (for example a ground level projection position of an aircraft), from two geographical coordinates, ‘a1' and 'a2' (for example an airport’s runway thresholds), of a great circle arc.

## Usage

 `1` ```along_track_distance(b, a1, a2) ```

## Arguments

 `b` the geographical coordinates (WGS84) of a body: a vector of longitude, latitude (in decimal degrees) and eventually altitude (in meters) `a1` the geographical coordinates (WGS84) of one end of a great circle arc: a vector of longitude, latitude (in decimal degrees) and eventually altitude (in meters) `a2` the geographical coordinates (WGS84) of the other end of a great circle arc: a vector of longitude, latitude (in decimal degrees) and eventually altitude (in meters)

## Value

the surface along-track distances from ‘b'’s cross-track intersection to 'a1' - 'a2'

Other utilities: `altitude_azimuth_distance()`, `cross_track_distance()`, `cross_track_intersection()`
 ```1 2 3 4 5 6 7 8 9``` ```## Not run: 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) along_track_distance(b, a1, a2) ## End(Not run) ```