R: Along Track Distance

alongTrackDistance {geosphere} | R Documentation

## Along Track Distance

### Description

The "along track distance" is the distance from the start point (p1) to the closest point on the path to a third point (p3), following a great circle path defined by points p1 and p2. See `dist2gc` for the "cross track distance"

### Usage

    alongTrackDistance(p1, p2, p3, r=6378137)

### Arguments

`p1` | longitude/latitude of point(s). Can be a vector of two numbers, a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialPoints* object
`p2` | as above
`p3` | as above
`r` | radius of the earth; default = 6378137m

### Value

A distance in units of r (default is meters)

### Author(s)

Ed Williams and Robert Hijmans

### See Also

`dist2gc`

### Examples

    alongTrackDistance(c(0,0),c(60,60),c(50,40))

[Package geosphere version 1.5-5 Index]