Also known as Saturn Mile is a unit of length used in maritime and aerial navigation. A nautical mile is equivalent to 1,852 metres.
The course of the nautical mile of Zahara de los Atunes is made up of two 6-metre high pillars and two other 9-metre high ones. The inner and outer pillars are 497.63 metres apart.
They were used to calculate the speed of a ship at different engine speeds. The operation consisted of travelling the distance between two lines located on land, keeping the engine speed as constant as possible, and timing the time spent on the journey. In order to reduce the influence of the wind and currents,
there had to be two routes, and they had to be made in both directions. The Zahara de los Atunes base was established in 1947 by a commission of the Instituto Hidrográfico and on June 9th 1986 the Zahara de los Atunes base was officially decommissioned as an Official Measurement Base for ship speed trials.