Alpha (navigation)

Alpha, also known as RSDN-20, is a Russian system for long range radio navigation.

RSDN in Russian stands for Радиотехническая Система Дальней Навигации (radiotehnicheskaya Sistema Dal'ney Navigatsii), which translates to English as "radio-technical long-distance navigation system".

Alpha coverage is up to 10,000 km from the master station, with a position error of 2.5 to 7 kilometres (2 to 4 mi).

The Alpha system consists of three transmitters, placed in the proximity of Novosibirsk, Krasnodar and Khabarovsk.

[1] A radio fix is taken by measuring the phase difference of the received signals.