# geod: Geodesic Distances In pegas: Population and Evolutionary Genetics Analysis System

## Description

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

## Usage

 `1` ```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.

## References

`geoTrans`, `as.dist`
 ```1 2 3 4 5 6 7``` ```## 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 ```