Antipodean Islands


Campbell Island

On a recent trip, I visited Campbell Island, the Southern-most of New Zealand’s extraordinary sub-antarctic islands. A fellow visitor from Ireland pointed out that Campbell is the land mass furthest from home i.e. Campbell Island is the true Irish antipode.  I had always assumed (wrongly) that this distinction was held by the eponymous Antipodes Island.

The situation is shown below. Black dots mark the centroids of the small sub-antarctic islands after reflection through the centre of the earth.


Colours show which dot is nearest, using geodesic distances on an ellipsoidal earth. This is just an ordinary Voronoi diagram, expect that the curvature of the Earth is taken into account accurately. (distGeo() function from R‘s geosphere package).

Campbell is the antipode for Ireland and Scotland, while Antipodes Island is antipode for England, Wales and Normandy (except for Anglesea and a sliver of Cumbria).

Ocean drifters



The map shows tracks of drifting buoys deployed in the southern ocean between 2005 and 2016. The underlying dataset consists of 15-minute gps data collected from 4608 buoys, available from NOAA Colour indicates speed of drift.

This is simply a visualisation of the raw drifter data with no further analysis or modelling. Nevertheless all of the well-known features of the surface circulation in the southern ocean emerge; Antarctic Circumpolar Drift, western boundary currents along the western coasts of South America (Brazil Current) and Africa (Agulhas),  powerful Agulhas Return Current in the Southern Indian Ocean, South Atlantic gyre (centred NorthEast of the Falkland Islands) etc.

R code

A dataframe buoydata was created using fread(),

transformed to a stereographic coordinates using spTransform()

and plot using geom_path()

Note the use of transparency (alpha). This can be varied to highlight different aspects of the flow.