The sea surface reflects the radar signal away from the satellite, making water appear dark in the image. This contrasts metal objects, such as ships, which appear as bright dots in the dark water. Boats that sailed through the English Channel in 2016 appear in blue, those from 2017 appear in green, and those from 2018 appear in red.
Due to its narrowness, as well as its strategic connection of the Atlantic Ocean and the North Sea, the Channel is very busy with east-west ship traffic. Because of the volume of ships passing through daily, a two-lane scheme is used, in order to prevent collisions.
Connecting Dover in England to Calais in northern France, the Strait of Dover is a major route, featuring more than 400 vessels crossing every day. The shortest distance across the Channel is just 33 km, making it possible to see the opposite coastline on a clear day.