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  2. Horizontal coordinate system - Wikipedia

    en.wikipedia.org/wiki/Horizontal_coordinate_system

    Azimuth is measured eastward from the north point (sometimes from the south point) of the horizon; altitude is the angle above the horizon. The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane to define two angles of a spherical coordinate system: altitude and azimuth.

  3. Spherical coordinate system - Wikipedia

    en.wikipedia.org/wiki/Spherical_coordinate_system

    The elevation is the signed angle from the x-y reference plane to the radial line segment OP, where positive angles are designated as upward, towards the zenith reference. Elevation is 90 degrees (= ⁠ π / 2 ⁠ radians) minus inclination. Thus, if the inclination is 60 degrees (= ⁠ π / 3 ⁠ radians), then the elevation is 30 degrees ...

  4. Altitude - Wikipedia

    en.wikipedia.org/wiki/Altitude

    The rate of decrease of temperature with elevation is known as the adiabatic lapse rate, which is approximately 9.8 °C per kilometer (or 5.4 °F [3.0 °C] per 1000 feet) of altitude. [ 12 ] The presence of water in the atmosphere complicates the process of convection.

  5. Grade (slope) - Wikipedia

    en.wikipedia.org/wiki/Grade_(slope)

    (This is the angle α opposite the "rise" side of a triangle with a right angle between vertical rise and horizontal run.) as a percentage, the formula for which is which is equivalent to the tangent of the angle of inclination times 100. In Europe and the U.S. percentage "grade" is the most commonly used figure for describing slopes.

  6. Solid angle - Wikipedia

    en.wikipedia.org/wiki/Solid_angle

    Solid angles can also be measured in square degrees (1 sr = (180/ π) 2 square degrees), in square arc-minutes and square arc-seconds, or in fractions of the sphere (1 sr = ⁠ 1 / 4 π ⁠ fractional area), also known as spat (1 sp = 4 π sr). In spherical coordinates there is a formula for the differential,

  7. Geodetic coordinates - Wikipedia

    en.wikipedia.org/wiki/Geodetic_coordinates

    Longitude measures the rotational angle between the zero meridian and the measured point. By convention for the Earth, Moon and Sun, it is expressed in degrees ranging from −180° to +180°. For other bodies a range of 0° to 360° is used. For this purpose, it is necessary to identify a zero meridian, which for Earth is usually the Prime ...

  8. Angular diameter - Wikipedia

    en.wikipedia.org/wiki/Angular_diameter

    Angular diameter: the angle subtended by an object. The angular diameter, angular size, apparent diameter, or apparent size is an angular separation (in units of angle) describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is the angular aperture (of ...

  9. Vertical position - Wikipedia

    en.wikipedia.org/wiki/Vertical_position

    height: "the vertical distance of a level, a point or an object considered as a point, measured from a specific datum." [2] ICAO further defines: elevation: "the vertical distance of a point or a level, on or affixed to the surface of the earth, measured from mean sea level." [2] I.e., elevation would be the altitude of the ground or a building.