They make a basically static visualization. I wanted to see the ships in motion. Plus, Dael Norwood made some guesses about the increasing prominence of Pacific trade in the period that I would like to see confirmed. That got me interested with the ship data that they use, which consists of detailed logbooks that have been digitized for climatological purposes. On the more technical side, I have been fiddling a bit lately with ffmpeg and ggplot (two completely unrelated systems, despite what the names imply) to make animated visualizations, and wanted to put one up. And it's an interesting case; historical data was digitized for climatological purposes, which means visualization is going to be on of the easiest ways to think about whether it might be usable for historical demonstration or analysis, as well.