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  2. Pressure altitude - Wikipedia

    en.wikipedia.org/wiki/Pressure_altitude

    In aviation, pressure altitude is the height above a standard datum plane (SDP), which is a theoretical level where the weight of the atmosphere is 29.921 inches of mercury (1,013.2 mbar; 14.696 psi) as measured by a barometer. [2] It indicates altitude obtained when an altimeter is set to an agreed baseline pressure under certain circumstances ...

  3. Conversion of units - Wikipedia

    en.wikipedia.org/wiki/Conversion_of_units

    Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to include replacement of a quantity with a corresponding quantity that describes the same physical property ...

  4. Geographic coordinate conversion - Wikipedia

    en.wikipedia.org/wiki/Geographic_coordinate...

    Geographic coordinate conversion has applications in cartography, surveying, navigation and geographic information systems. In geodesy, geographic coordinate conversion is defined as translation among different coordinate formats or map projections all referenced to the same geodetic datum. [1] A geographic coordinate transformation is a ...

  5. Nautical mile - Wikipedia

    en.wikipedia.org/wiki/Nautical_mile

    A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute (⁠ 1 / 60 ⁠ of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).

  6. Barometric formula - Wikipedia

    en.wikipedia.org/wiki/Barometric_formula

    Pressure as a function of the height above the sea level. There are two equations for computing pressure as a function of height. The first equation is applicable to the atmospheric layers in which the temperature is assumed to vary with altitude at a non null lapse rate of : = [,, ()] ′, The second equation is applicable to the atmospheric layers in which the temperature is assumed not to ...

  7. Height above mean sea level - Wikipedia

    en.wikipedia.org/wiki/Height_above_mean_sea_level

    Height above mean sea level is a measure of a location's vertical distance (height, elevation or altitude) in reference to a vertical datum based on a historic mean sea level. In geodesy, it is formalized as orthometric height. The zero level varies in different countries due to different reference points and historic measurement periods.

  8. Decimal degrees - Wikipedia

    en.wikipedia.org/wiki/Decimal_degrees

    Decimal degrees (DD) is a notation for expressing latitude and longitude geographic coordinates as decimal fractions of a degree. DD are used in many geographic information systems (GIS), web mapping applications such as OpenStreetMap, and GPS devices. Decimal degrees are an alternative to using sexagesimal degrees (degrees, minutes, and ...

  9. Metre - Wikipedia

    en.wikipedia.org/wiki/Metre

    The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of ⁠ 1 / 299 792 458 ⁠ of a second, where the second is defined by a hyperfine transition frequency of caesium.