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  2. Line-of-sight propagation - Wikipedia

    en.wikipedia.org/wiki/Line-of-sight_propagation

    Assuming a perfect sphere with no terrain irregularity, the distance to the horizon from a high altitude transmitter (i.e., line of sight) can readily be calculated. Let R be the radius of the Earth and h be the altitude of a telecommunication station. The line of sight distance d of this station is given by the Pythagorean theorem;

  3. Horizon - Wikipedia

    en.wikipedia.org/wiki/Horizon

    View of the ocean with two ships: one in the foreground and one to the left of it on the horizon. Historically, the distance to the visible horizon has long been vital to survival and successful navigation, especially at sea, because it determined an observer's maximum range of vision and thus of communication, with all the obvious consequences for safety and the transmission of information ...

  4. Sextant - Wikipedia

    en.wikipedia.org/wiki/Sextant

    A sextant. A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.

  5. Cosmological horizon - Wikipedia

    en.wikipedia.org/wiki/Cosmological_horizon

    The particle horizon, also called the cosmological horizon, the comoving horizon, or the cosmic light horizon, is the maximum distance from which light from particles could have traveled to the observer in the age of the universe. It represents the boundary between the observable and the unobservable regions of the universe, so its distance at ...

  6. Intercept method - Wikipedia

    en.wikipedia.org/wiki/Intercept_method

    In astronomical navigation, the intercept method, also known as Marcq St. Hilaire method, is a method of calculating an observer's position on Earth (geopositioning).It was originally called the azimuth intercept method because the process involves drawing a line which intercepts the azimuth line.

  7. Bearing (navigation) - Wikipedia

    en.wikipedia.org/wiki/Bearing_(navigation)

    In land navigation, a 'bearing' is ordinarily calculated in a clockwise direction starting from a reference direction of 0° and increasing to 359.9 degrees. [5] Measured in this way, a bearing is referred to as an azimuth by the US Army but not by armies in other English speaking nations, which use the term bearing. [6]

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    mail.aol.com

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  9. Particle horizon - Wikipedia

    en.wikipedia.org/wiki/Particle_horizon

    The particle horizon (also called the cosmological horizon, the comoving horizon (in Scott Dodelson's text), or the cosmic light horizon) is the maximum distance from which light from particles could have traveled to the observer in the age of the universe.