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  2. List of extreme points of Vietnam - Wikipedia

    en.wikipedia.org/wiki/List_of_extreme_points_of...

    Similarly, a positive longitude value refers to the eastern hemisphere, and a negative value refers to the western hemisphere. The coordinates used in this article are sourced from Google Earth, which makes use of the WGS84 geodetic reference system. Additionally, a negative altitude value refers to land below sea level.

  3. Horizontal coordinate system - Wikipedia

    en.wikipedia.org/wiki/Horizontal_coordinate_system

    The following are two independent horizontal angular coordinates: Altitude (alt. or altitude angle [b]), sometimes referred to as elevation (el. or elevation angle [c]) or apparent height, is the angle between the object and the observer's local horizon. For visible objects, it is an angle between 0° and 90°.

  4. Altitude - Wikipedia

    en.wikipedia.org/wiki/Altitude

    Pressure altitude is the elevation above a standard datum air-pressure plane (typically, 1013.25 millibars or 29.92" Hg). Pressure altitude is used to indicate "flight level" which is the standard for altitude reporting in the U.S. in Class A airspace (above roughly 18,000 feet).

  5. Height above mean sea level - Wikipedia

    en.wikipedia.org/wiki/Height_above_mean_sea_level

    A geoid is needed to convert the 3D position to sea-level elevation. Pressure altimeter measuring atmospheric pressure, which decreases as altitude increases. Since atmospheric pressure varies with the weather, too, a recent local measure of the pressure at a known altitude is needed to calibrate the altimeter. Stereoscopy in aerial photography.

  6. ISO 6709 - Wikipedia

    en.wikipedia.org/wiki/ISO_6709

    ISO 6709, Standard representation of geographic point location by coordinates, is the international standard for representation of latitude, longitude and altitude for geographic point locations. The first edition ( ISO 6709:1983 ) was developed by ISO/IEC JTC 1 /SC 32.

  7. Geographic coordinate system - Wikipedia

    en.wikipedia.org/wiki/Geographic_coordinate_system

    A geographic coordinate system (GCS) is a spherical or geodetic coordinate system for measuring and communicating positions directly on Earth as latitude and longitude. [1] It is the simplest, oldest and most widely used type of the various spatial reference systems that are in use, and forms the basis for most others.

  8. Altitude (disambiguation) - Wikipedia

    en.wikipedia.org/wiki/Altitude_(disambiguation)

    Altitude (astronomy), one of the angular coordinates of the horizontal coordinate system; Altitude (triangle), in geometry, a line passing through one vertex of a triangle and perpendicular to the opposite side

  9. Altitude-azimuth - Wikipedia

    en.wikipedia.org/wiki/Altitude-azimuth

    Altitude-azimuth, alt-azimuth, or alt-az may refer to: Horizontal coordinate system, or altitude-azimuth coordinates; Altazimuth mount, a two-axis telescope mount