31.6 million ship positions on one map
The count is 31,648,998 recorded ship positions, logged over 96 hours in January 2023. That works out to an average of about 91 position reports per second, around the clock, for four days. The map below draws them at once, and the server redraws from the source records when you pan or zoom. Drag toward a port you know, zoom in, and use the controls on the left to filter by ship type and speed.
31,648,998 records · 96 hours · Source: AIS
What it takes to draw 31 million dots
Where the records come from
Ships broadcast their position by radio, a system called AIS, and U.S. coastal receivers log the signals. The government publishes the records. This map uses 31,648,998 positions from the public log for January 1 to 4, 2023. A dot marks one ship at one moment.
One image instead of 31 million dots
That many dots is far more than a browser can draw smoothly. So the server bins the positions into small screen patches, counts what lands in a patch, shades by count, and sends a single rendered image back to your browser. Busy lanes read bright. Empty water reads dark.
A fresh count on demand
Pan or zoom and the server runs the count again for the area on screen. Zoom from the full coastline down to a single harbor and the structure keeps resolving, because the math runs on the source records rather than a saved screenshot.
The binning method is the same one used for collections in the billions of positions. Bigger numbers need bigger hardware, and this demo runs on a standard server, so 31.6 million is the size that stays quick. The shading ranks patches against the rest of the current view, so compare areas to one another rather than reading exact ship counts.