DATED 1888 and with British Government “BROAD ARROW” that signifies that this Altimiter was once British Government Property and likely produced for a Military Contract. The previous owner advised that he believed that this was USED by the fledgling British Army ROYAL FLYING CORPS who did initially use BALLOONS and later early Biplane like aircraft that would NOT have had a great deal of instrumentation compared to later WW2 era or “modern” aircraft. An altimeter or an altitude meter is an instrument used to measure the altitude. Of an object above a fixed level. The measurement of altitude is called altimetry , which is related to the term bathymetry. The measurement of depth under water. A barometric altimeter, used along with a topographic map, can help to verify one’s location. It is more reliable, and often more accurate, than a GPS receiver for measuring altitude; the GPS signal may be unavailable, for example, when one is deep in a canyon, or it may give wildly inaccurate altitudes when all available satellites are near the horizon. Because barometric pressure changes with the weather, hikers must periodically re-calibrate their altimeters when they reach a known altitude, such as a trail junction or peak marked on a topographical map. Altitude can be determined based on the measurement of atmospheric pressure. The greater the altitude, the lower the pressure. When a barometer is supplied with a nonlinear calibration so as to indicate altitude, the instrument is called a pressure altimeter or barometric altimeter. A pressure altimeter is the altimeter found in most aircraft. And skydivers use wrist-mounted versions for similar purposes. Hikers and mountain climbers use wrist-mounted or hand-held altimeters, in addition to other navigational tools such as a map, magnetic compass, or GPS receiver. The calibration of an altimeter follows the equation. \displaystyle z=c\;T\;\log(P_{o}/P). Where c is a constant, T is the absolute temperature, P is the pressure at altitude z, and P. Is the pressure at sea level. The constant c depends on the acceleration of gravity and the molar mass of the air. However, one must be aware that this type of altimeter relies on “density altitude” and its readings can vary by hundreds of feet owing to a sudden change in air pressure, such as from a cold front, without any actual change in altitude. ALL my items are GUARANTEED 100% GENUINE, the GUARANTEE is GOOD for “life”. Track Page Views With. Auctiva’s FREE Counter. Add a map to your own listings. The item “Antique Altitude ALTIMETER 1888 British BROAD ARROW Marking by T. Wheeler London” is in sale since Thursday, November 02, 2017. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “phillip_in_new_zealand” and is located in Auckland (aprox. 12,000 “clicks” from USA). This item can be shipped worldwide.
- Maker: T. Wheeler Scientific Instruments London UK 1888
- Original/Reproduction: Original
- Balonist Mountain Climber Geographer: Brass Glass Leather enamel face Blued Steel hand
