The locations of ship weather observations rescued by the participants in Weather Detective (weatherdetective.net.au/).
To be used, an observation must have been transcribed by at least two people, who agree on the value transcribed, and the location of the observation must be known (given or inferred) As of September 2015, 56,253 observations had reached this stage.
The video covers one year at 4 days per second. The new observations are spread out across several years (the majority in 1893-1895). To keep the video short and snappy they are shown as if they occurred in the same year. Each observation appears for a 24-hour period (0.25s screen time) centred on the time of the observation (i.e. 1 day's worth of observations is shown at each time).