altimeter

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altimeter

(ăltĭm`ĭtər, ăl`tĭmē'tər), device for measuring altitude. The most common type is an aneroid barometerbarometer
, instrument for measuring atmospheric pressure. It was invented in 1643 by the Italian scientist Evangelista Torricelli, who used a column of water in a tube 34 ft (10.4 m) long.
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 calibrated to show the drop in atmospheric pressure in terms of linear elevation as an airplane, balloon, or mountain climber rises. It shows height above sea level, but not above such land features as hills, mountains, and valleys. The radio altimeter, or terrain-clearance indicator, is an absolute altimeter; it indicates the actual altitude over water or over terrain, however uneven. It operates by first sending either continuous or pulse radio signals from a transmitter in an aircraft to the earth's surface. A receiver in the aircraft then picks up the reflection of the signals from the surface. The time it takes for the signals to travel to the earth and back is converted automatically into absolute altitude that can then be read from a calibrated indicator. The radio altimeter is used in the automatic landing systems of aerospace vehicles; systems developed from radio altimeters can automatically control military aircraft flying at high speeds and low altitudes.
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altimeter

[al′tim·əd·ər]
(engineering)
An instrument which determines the altitude of an object with respect to a fixed level, such as sea level; there are two common types: the aneroid altimeter and the radio altimeter.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

altimeter

altimeter
Altimeter indicator dial.
altimeter
Construction of a simple altimeter.
An instrument to indicate the height of an aircraft above a predetermined datum, normally sea level. Specifically, an instrument similar to an aneroid barometer that utilizes the change of atmospheric pressure with altitude to indicate the approximate elevation above a given point or plane used as a reference. A simple pressure altimeter is an airtight metal case, the interior of which is kept at atmospheric pressure by a tube connecting it to the static tube of the ASI (airspeed indicator). Inside the instrument case, a partially evacuated aneroid capsule is secured at the center of one of its faces to a base rigidly fixed to the casing. A leaf spring prevents the collapse of the capsule. The capsule expands as aircraft gains height. The expansion of the capsule is converted into height through a system of gears. A pressure altimeter suffers from barometric, temperature, instrument, and lag errors. Radio or radar altimeters indicate heights above ground level.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved

altimeter

an instrument that indicates height above sea level, esp one based on an aneroid barometer and fitted to an aircraft
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
However, it is justified due to the lower altimetric amplitude and the smaller distance from the main riverbed.
But in addition, the complete altimetric record, which begins in 1992, is employed (e.g., Fu and Cazenave 2001) and a mean topography constructed from it (Andersen et al.
The distance between municipality i and its neighbor j is [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], where [x.sub.k] are the following eleven variables: per capita current expenditure, population density, per capita grants, entrepreneurial intensity, per capita PIT tax base, tourism intensity, average household size, incidence of foreigners, altimetric zone, net migration rate, birth rate.
Systematic morphometric study including drainage; altimetric; hypsometric and lineament analyses was carried out and the results are discussed.
In this paper, we shall discuss in the context of airborne altimetric LiDAR.
Moreover, one of the most important bases to resolve this problem is to use the global geoid with the gravity geopotential [[bar.W].sub.0] = 62636 856.0 [m.sup.2]*[s.sup.-2], that has been determined from altimetric data analysis (Bursa et al.
Three topographic variables per plot were calculated from the plot corner coordinates: (1) vertical distance from the river (the difference between the average altimetric level of the four corners of the plot and the altimetric level of the river); (2) topographic unevenness (the difference between the maximum and minimum altimetric levels of the plot); and (3) average declivity (average of the declivity on the four sides of the plot).
The altimetric range of Valsan catchment is over 2000m in north part with main peaks Scarisoara, Picuiata, Jepi.
TABLE 1 Mean value and standard deviation (SD) of limnological and environmental variables measured at Barra Bonita Reservoir during study period and result of Spearman correlation Variables Mean value [+ or -] SD Spearman correlation pH 7.0 [+ or -] 0.75 0.2809 * Temperature ([degrees]C) 25.4 [+ or -] 3.60 -0.2286 * Dissolved oxygen (mg/L) 6.47 [+ or -] 2.75 0.2191 * Electric conductivity ([micro]s.cm) 319.17 [+ or -] 68.19 0.2936 * Transparency (m) 0.73 [+ or -] 0.20 0.2875 * Alkalinity (mEQ/L) 0.92 [+ or -] 0.19 0.0516 Chlorophyll a ([micro]g/L) 384.3 [+ or -] 238.3 0,2404 * Monthly accumulated pluviosity (mm) 86.17 [+ or -] 70.78 -0.0751 * Altimetric benchmark (m) 449.66 [+ or -] 1.45 -0.1945 * * statistical differences (p<0.05).