Granas (Global RAdio NAvigation System) is a satellite-based radio navigation system with global coverage, high accuracy and continuous availability for civil users on land, sea and air. Its performance, thus, is superior to existing ground-based radio navigation systems as Omega, Loran, Decca, and so on.

The principle of Granas user-position determination is similar to that of Navstar GPS or Navsat in that a user makes pseudo-range measurements to a number of satellites visible above a 5° elevation angle. These ranging operations are performed using time-of-arrival (TOA) measurements of navigation signals transmitted by satellites. Knowing the discrete positions of four or more satellites and their pseudo-ranges, a user may compute its own clock bias and its position in three dimensions (longitude, latitude and altitude).