R: Geodesic Distances

geod {pegas} | R Documentation

## Geodesic Distances

### Description

This function calculates geodesic (or great-circle) distances between pairs of points with their longitudes and latitudes given in (decimal) degrees.

### Usage

    geod(lon, lat = NULL, R = 6371)

### Arguments

`lon` | either a vector of numeric values with the longitudes in degrees, or, if `lat = NULL`, a matrix giving the longitudes (first column) and the latitudes (second column).
`lat` | a vector with the latitudes.
`R` | the mean radius of the Earth (see details).

### Details

The default value of `R` is the mean radius of the Earth which is slightly smaller than the radius at the equator (6378.1 km).

### Value

a numeric symmetric matrix with the distances between pairs of points in kilometres.

### Author(s)

Emmanuel Paradis

### References

http://en.wikipedia.org/wiki/Great-circle_distance

http://en.wikipedia.org/wiki/Earth

### See Also

`geoTrans`, `as.dist`

### Examples

    ## the distance between 0N 0E and 0N 180E...
    geod(c(0, 180), c(0, 0)) # ~ 20015.09 km
    ## ... the same using the radius of the Earth at the equator:
    geod(c(0, 180), c(0, 0), 6378.1) # ~ 20037.39 km
    ## The same comparison for two points 5 degrees apart:
    geod(c(0, 5), c(0, 0)) # ~ 555.9746 km
    geod(c(0, 5), c(0, 0), 6378.1) # ~ 556.5942 km

[Package pegas version 0.13 Index]