Altimeter is an instrument that measures the altitude (height) above a reference level (not necessarily sea level), and it could be found on board of the gliders and aircrafts.It shows the height of flight above the aerodrome of departure and it is based on the decrease of air pressure, in relation to height.
In fact it is a barometer, with indications in units of height. The use of the mercury barometer in gliding and aviation is virtually impossible, because of the relatively sudden changes of speed and height and, therefore,it is replaced by a metal vacuumed capsule, made of very thin sheet.The walls of the capsule are very elastic and they are deforming, under the action of atmospheric pressure. The deflection,which is proportional to external pressure changes, via a transmission system, is headed to a pointer, which moves in front of a dial, which is calibrated in units of height.
If the glider or the airplane climbs,the atmospheric pressure decreases, elastic walls of the capsule meeting a lower resistance, so the capsule expands, putting in motion the mechanism of transmission which, in turn, gives to the indicator needle a movement, which is proportional to the amount of distortion. On the dial of the device are shown units of pressure and amount of the corresponding heights.
Anyway, there is no such a device as "altomometer", but there is an instrument called altometer, which is a theodolite.
Theodolite is an instrument for measuring horizontal angles (angle from zenith) and vertical (vs. horizontal),and it is used in geodesy and mining.
Measurements are made with a stand that is adjustable by using aspirit level. The instrument is equipped with a graduated eyepiece telescope which helps the operator for precise targeting of a point on the ground, the angles vertical or horizontal being determined by means of graduated dials.
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