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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | |
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First Edition Preface Second Edition Preface Acknowledgments
Section A A index 431-439 of 917 terms
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altigraph—A recording altimeter.
altimeter corrections—Corrections that must be made to the readings of a pressure altimeter to obtain true altitudes. There are several sources of corrections: 1) pressure corrections due to changes in sea level atmospheric pressure readings; 2) air temperature corrections resulting from the differences between the actual temperature of the column of air beneath the altimeter and a standard atmosphere temperature profile; and 3) corrections for errors in the calibration of the mechanical parts of the altimeter.
altimeter equation—The form of the hydrostatic equation used to compute the altimeter setting, which is the pressure “reduced” to sea level using the temperature profile of the ICAO (International Civil Aeronautical Organization) standard atmosphere.
altimeter-setting indicator—A precision aneroid barometer calibrated to indicate directly the local sea level altimeter setting.
altimeter setting—Value of the atmospheric pressure used to adjust the subscale of a pressure altimeter so that it indicates the height of an aircraft above a known reference surface.
altimeter—An instrument that determines the altitude of an object with respect to a fixed level. There are several types of altimeters: 1) the pressure altimeter, which measures barometric pressure and converts it to altitude above sea level when referenced to the existing measured sea level barometric pressure, or to pressure altitude when referenced to a standard pressure; 2) the radio or radar altimeter, which deduces altitude by measuring the time it takes a radio signal to travel from a transmitter to the underlying surface and back to the receiver; and 3) the Global Positioning System (GPS), which determines altitude by measuring time of travel of radio signals between GPS-equipped satellites and the receiver.
altimetry—The measurement of altitude or height. In aeronautical science, altimetry is equivalent to hypsometry.
altithermal period—The period from about 5000–2500 B.C., proposed by Ernst V. Antevs (1952), during which the summer temperature of western North America was 1°–2°C warmer than today and during which the lakes of the American Great Basin dried.
Antevs, E., 1952: Cenozoic climates of the Great Basin. Sonderdruck aus der Geologischen Rundschau, Bd. 40, Heft 1, 94–108.
altitude—1. A measure (or condition) of height, especially of great height, as a mountain top or aircraft flight level. In meteorology, altitude is used almost exclusively with respect to the height of an airborne object above the earth's surface, above a constant-pressure surface, or above mean sea level. The measurement of altitude is accomplished by altimeters in aeronautics, and the entire study is called altimetry. Compare elevation. 2. In astronomy, same as elevation angle.
altocumulus castellanus—See castellanus.
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