I recently stumbled upon a fascinating dataset which contains digitised information from the log books of ships (mostly from Britain, France, Spain and The Netherlands) sailing between 1750 and 1850. The creation of this dataset was completed as part of the Climatological Database for the World’s Oceans 1750-1850 (CLIWOC) project. The routes are plotted from the lat/long positions derived from the ships’ logs. I have played around with the original data a little to clean it up (I removed routes where there was a gap of over 1000km between known points, and only mapped to the year 1800). As you can see the British (above) and Spanish and Dutch (below) had very different trading priorities over this period. What fascinates me most about these maps is the thousands (if not millions) of man hours required to create them. Today we churn out digital spatial information all the time without thinking, but for each set of coordinates contained in these maps a ship and her crew had to sail there and someone had to work out a location without GPS or reliable charts.

These maps were produced with the latest version of R‘s ggplot2, maptools, geosphere and png packages. Formatting the data took the most work (it was a very large MS Access database). I used ggplot’s annotation_raster() to add the compass rose and title.

Update: For some nice animations and a much better critical analysis of the data see Ben Schmidts blog.