geodist() R function from [gmt]

Distance Between Geographic Coordinates

Calculate surface distance between geographic coordinates. UTF-8


geodist(Nfrom, Efrom, Nto, Eto, units="km")

Nfrom: latitude of origin.
Efrom: longitude of origin.
Nto: latitude of destination.
Eto: longitude of destination.
units: how distance is measured: "km" for kilometres, "nm" for nautical miles.

Latitude and longitude are passed as decimal numbers, e.g. 66.5 for 66 $°$ 30 $'$ N. Vectors of coordinates are supported.

Vector of distances.

The surface distance between geographic coordinates is:

D \:=\: \cos^{-1}\!\!\big[\:\!\!\sin\theta_1\sin\theta_2 \,+\,\cos\theta_1\cos\theta_2\cos(\phi_1\;\!\!\!-\!\phi_2)\big]D = acos( sin(N1)*sin(N2) + cos(N1)*cos(N2)*cos(E1-E2) )

where distance and coordinates are expressed in radians. $N1$ and $N2$ is the latitude of origin and destination, and $E1$ and $E2$ is longitude.

The calculations assume a perfect sphere and elevation differences are ignored. The SI definition of a nautical mile is exactly 1.852 km.


geodist(55.75,37.63, 39.9,116.4)  # Moscow - Beijing
geodist(90,0, -90,0, "nm")        # from pole to pole