Where would HMS Belfast hit right now?

HMS Belfast is famously said to have its guns pointed to hit London Gateway services, 18.7 km away. But, I wanted to see how correct that fact is given real ballistic simulation, so this page works out where a shell fired by HMS Belfast would land, given current atmospheric conditions.

A point-mass ballistics engine simulates the shell, with drag tuned to HMS Belfast's own range tables. Real wind data at every altitude of the ballistic arc, air density and humidity, Earth curvature, Coriolis, spin drift, the Thames tide height, the powder magazine temperature, and LIDAR ground elevation at the impact point, are all fed into the simulation. The output is one likely impact point and a Circular Error Probable: how far off that single shell might land, given round-to-round gun scatter and the spread of the weather forecast ensembles.

A combination of OpenStreetMap data, and a Claude vision model that reads the rendered impact map describes where HMS Belfast would hit. The ballistic simulation is re-run every hour, with previous simulations available to display, to see how the predicted impact location changes as atmospheric conditions change.