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  2. Spherical coordinate system - Wikipedia

    en.wikipedia.org/wiki/Spherical_coordinate_system

    Even with these restrictions, if the polar angle (inclination) is 0° or 180°—elevation is −90° or +90°—then the azimuth angle is arbitrary; and if r is zero, both azimuth and polar angles are arbitrary. To define the coordinates as unique, the user can assert the convention that (in these cases) the arbitrary coordinates are set to zero.

  3. GNSS reflectometry - Wikipedia

    en.wikipedia.org/wiki/GNSS_reflectometry

    GNSS-R system diagram GNSS reflectometry (or GNSS-R) involves making measurements from the reflections from the Earth of navigation signals from Global Navigation Satellite Systems such as GPS . The idea of using reflected GNSS signals for earth observation was first proposed in 1993 by Martin-Neira. [ 1 ]

  4. Beta angle - Wikipedia

    en.wikipedia.org/wiki/Beta_angle

    The value of a solar beta angle for a satellite in Earth orbit can be found using the equation = ⁡ [⁡ ⁡ ⁡ ⁡ ⁡ ⁡ ⁡ + ⁡ ⁡ ⁡ ()] where is the ecliptic true solar longitude, is the right ascension of ascending node (RAAN), is the orbit's inclination, and is the obliquity of the ecliptic (approximately 23.45 degrees for Earth at present).

  5. Plan position indicator - Wikipedia

    en.wikipedia.org/wiki/Plan_position_indicator

    The radar antenna sends pulses while rotating 360 degrees around the radar site at a fixed elevation angle. It can then change angle or repeat at the same angle according to the need. Return echoes from targets are received by the antenna and processed by the receiver and the most direct display of those data is the PPI.

  6. Communications satellite - Wikipedia

    en.wikipedia.org/wiki/Communications_satellite

    Syncom 2 was the first communications satellite in a geosynchronous orbit. It revolved around the Earth once per day at constant speed, but because it still had north–south motion, special equipment was needed to track it. [19] Its successor, Syncom 3, launched on 19 July 1964, was the first geostationary communications satellite. Syncom 3 ...

  7. Omnidirectional antenna - Wikipedia

    en.wikipedia.org/wiki/Omnidirectional_antenna

    In radio communication, an omnidirectional antenna is a class of antenna which radiates equal radio power in all directions perpendicular to an axis (azimuthal directions), with power varying with angle to the axis (elevation angle), declining to zero on the axis.

  8. Aerial photographic and satellite image interpretation

    en.wikipedia.org/wiki/Aerial_photographic_and...

    For a location which has an elevation lower than that of the datum plane, the original position will move closer to the central point of the image. [4] Figure 11. This diagram shows an example of displacement. A is the location that is lower than the datum plane. It moves inward to the central point. B is the location that is higher than the ...

  9. Angle of arrival - Wikipedia

    en.wikipedia.org/wiki/Angle_of_arrival

    The angle of arrival (AoA) of a signal is the direction from which the signal (e.g. radio, optical or acoustic) is received. [1] Measurement.