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  2. Angular distance - Wikipedia

    en.wikipedia.org/wiki/Angular_distance

    Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere.

  3. 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.

  4. Meridian altitude - Wikipedia

    en.wikipedia.org/wiki/Meridian_altitude

    By subtracting this from 90°, he would find that the zenith distance is 90°, which is his latitude. Observer C at the same time is at latitude 20°N on the same meridian, i.e. on the same longitude as Observer A. His measured altitude would be 70°, and subtracting this from 90° gives a 20° zenith distance, which in turn is his latitude. In ...

  5. Geodetic coordinates - Wikipedia

    en.wikipedia.org/wiki/Geodetic_coordinates

    Geodetic latitude and geocentric latitude have different definitions. Geodetic latitude is defined as the angle between the equatorial plane and the surface normal at a point on the ellipsoid, whereas geocentric latitude is defined as the angle between the equatorial plane and a radial line connecting the centre of the ellipsoid to a point on the surface (see figure).

  6. Sextant - Wikipedia

    en.wikipedia.org/wiki/Sextant

    The frame of a sextant is in the shape of a sector which is approximately 1 ⁄ 6 of a circle (60°), [2] hence its name (sextāns, sextantis is the Latin word for "one sixth"). "). Both smaller and larger instruments are (or were) in use: the octant, quintant (or pentant) and the (doubly reflecting) quadrant [3] span sectors of approximately 1 ⁄ 8 of a circle (45°), 1 ⁄ 5 of a circle (72 ...

  7. Navigational triangle - Wikipedia

    en.wikipedia.org/wiki/Navigational_triangle

    Finding the latitude requires measuring the vertical angle (altitude) of X from the horizon using a sextant, the declination of X from a reference book, and a set of sight reduction Tables. The sun, moon, and planets move relative to the celestial sphere, but only the stars' hour angles change with the rotation of the earth, completing a full ...

  8. Geography of Europe - Wikipedia

    en.wikipedia.org/wiki/Geography_of_Europe

    Satellite image of Europe by night 1916 physical map of Europe Topography of Europe. Some geographical texts refer to a Eurasian continent given that Europe is not surrounded by sea and its southeastern border has always been variously defined for centuries. In terms of shape, Europe is a collection of connected peninsulas and nearby islands.

  9. 40th parallel north - Wikipedia

    en.wikipedia.org/wiki/40th_parallel_north

    The 40th parallel north is a circle of latitude that is 40 degrees north of the Earth's equatorial plane. It crosses Europe , the Mediterranean Sea , Asia , the Pacific Ocean , North America , and the Atlantic Ocean .