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    • Disadvantages of Other Positioning Systems

    Landmarks:
    Only work in local area. Subject to movement or destruction by environmental factors.
    Example: Big oak tree on the side of the road.

    Dead Reckoning:
    Very complicated. Accuracy depends on measurement tools which are usually relatively crude. Errors accumulate quickly.
    Example: A piece of land for fix location.

    Dead reckoning is a method of navigation used in ships, aircraft, trucks, cars, rail engines, construction sites engines e.g. in tunnels and, more recently, mobile robots. Essentially it is used to estimate an object's position based on the distance it traveled in its current direction from its previous position.
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    Celestial:
    Complicated. Only works at night in good weather. Limited precision.
    Example: Looking at Syrius at night.

    OMEGA:
    Based on relatively few radio direction beacons. Accuracy limited and subject to radio interference.
    Example: As of September 30, 1997, 0300 UT, the OMEGA Navigation System terminated.

    The OMEGA radionavigation system, developed by the United States Navy for military aviation users, was approved for full implementation in 1968 and promised a true worldwide oceanic coverage capability and the ability to achieve a four mile accuracy when fixing a position. Initially, the system was to be used for navigating nuclear bombers across the North Pole to Russia. Later, it was found useful for submarines.
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    LORAN:
    Limited coverage (mostly coastal). Accuracy variable, affected by geographic situation. Easy to jam or disturb.
    Example: LORAN (LOng RAnge Navigation).

    LORAN systems were up and running during World War II and were used extensively by the US Navy and Royal Navy. It was originally known as "LRN" for Loomis radio navigation, after millionaire and physicist Alfred Lee Loomis, who invented LORAN and played a crucial role in military research and development during WWII.
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    SatNav:
    Based on low-frequency doppler measurements so it's sensitive to small movements at receiver. Few satellites so updates are infrequent.
    Example: Satellite navigation system.

    The original motivation for satellite navigation was for military applications.
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