An altimeter, or as it is commonly called, an altimeter, is a flight and navigation device for measuring flight altitude. All altimeters are subdivided into two main types in terms of their structure, namely, radio and barometric instruments.

In the old days it was used as a basic altimeter goniometer, which allowed to determine the height of cosmic bodies, such as a star or a planet.

Barometric altimeter

With this device may determine the relative altitude. This device operates by measuring the pressure in the atmosphere. Everyone knows that with the rise in the height of the atmospheric pressure decreases. It is due to this principle and works altimeter. In fact, it does not measure the height and air pressure, which is determined based on the height.

Altimeter 3434

Structurally, the altimeter is a sealed box, which has a membrane. With the change in pressure diaphragm changes its position. To her between the membrane and the arrow of the device there is a connection. For this reason, the slightest change in the membrane are shown by an arrow on a graduated scale.

These altimeters installed in aircraft with a small maximum altitude. The device is similar to the clock, as it has a circular shape and the two arrows. The main difference is that the board is divided into 10 sectors. One of the arrows, moving one division, said in 100 meters height, and the second, smaller, said elevation changes 1 kilometer.

More modern barometric altimeters can measure altitudes up to 20 kilometers above sea level. It should be noted that this design is informally considered to be the standard in the aircraft industry. There are also one-arrow altimeters, a full rotation of 360 degrees corresponds to one kilometer of height. 

It should be noted that sometimes need manual adjustment altimeter given surface pressure on the ground, especially when they are located in mountainous areas. Because of incorrect altimeter setting happened many disasters, the risk increases with zero visibility.

In the CIS countries decided to establish the pressure on the device is the same as the pressure of the airfield, which is carried out planting, it can be considered a point of reference. Western countries as a reference point, a pressure altitude at sea level.

Another point of reference for the height is the so-called echelon line. The train is the standard pressure in 760 mm Hg. St., Which comes at a height. This is a conventional height line with constant pressure. This conventional height reference line is the standard for aviation worldwide. It should be noted that the landing of all aircraft is prohibited without clarifying the atmospheric pressure above the aerodrome. ICAO requirements state the mandatory presence on board a control altimeter, which, in addition to showing altitude, signals the aircraft respondent, all this allows air traffic controllers to determine the real altitude of the flight of the vessel.

Altimeter 34343

There are small altimeters, which use commandos and paratroopers jump. This device has a small weight and size, the body is made of impact-resistant material. These systems are installed on parachutes. Currently used and electronic devices that signal the passage of a predetermined height.

Of Radio Altimeter

A radio-type altimeter allows you to display the flight altitude by sending an electron wave in the direction of the earth, after which it is bounced off and received by the device on board the aircraft. The return time of the signal is analyzed, the height of the aircraft above the ground is determined. The main difference from the barometric altimeter is that the real altitude is determined, not the relative one. In addition, this device displays altitude with a greater degree of accuracy.

Yet in practice, the device is effective at low altitudes as high altitude requires a powerful transmitter signals and associated equipment to filter and eliminate interference.

Altimeter 44545

The system consists of a microwave transmitter and an antenna, which is located on the lower part of the aircraft fuselage. There are also reflectors and signal receivers, a processing and display system on the dashboard in the cockpit. Radiotechnical altimeters are divided into two types. The former operate at altitudes up to 1,5 kilometers in continuous mode. The latter operate in the range from 1,5 to 30 kilometers, but they operate in a pulsed mode. All altimeters are equipped with low-altitude signal systems, which sound and light indicate a decrease in altitude from a preset one.

The disadvantage of this device is that the beam from the transmitter is directed straight down. Due to this efficient of Radio Altimeter can be considered only on flat terrain and completely useless in mountainous areas. In addition, when a large roll machine tool displays inflated performance that is not true. Speaking of safety, it should be noted that such devices served the powerful short-wave pulses, which cause damage to the biosphere.


In aviation, the altitude can be measured using modern GPS receivers. This device works by sending signals to several satellites that are in permanent orbits of motion. Mathematical calculations of the device allow to accurately determine the coordinates of the aircraft and its height. The height is measured with respect to the earth model WGS84. It should be noted that the GPS device works with satellites. So with the help of communication with two satellites, you can set the exact coordinates. To determine the altitude of the flight, communication with three satellites is necessary. The operation of the altimeter GPS has much more advantages than barometric and radio engineering devices, since the determination of altitude does not depend on the pressure, terrain and aircraft heeling.

Yet there are some drawbacks to such devices. When used on high-speed fighters very rapid decline does not allow the instrument to display actual performance. In such a situation computing devices must be time to send and receive signals from the satellite, such delays can reach one second. Newer models of GPS-altimeters are able to take into account the rate of decline, making them more accurate.


For low altitudes more accurate and reliable are still barometric and radio altimeters, since they do not affect the signals reflected from the surface and interference from ground electrical systems.

Personal GPS-receivers, which are used in cars or mobile phones may be a deviation from accuracy to 10 meters, enough for effective land navigation. US military and intelligence agencies are using private and more accurate GPS channel called L1, which measures the accuracy of the height of a few centimeters.

Gamma-ray altimeter

The principle of operation of this device is based on the emission of isotopes 137Cs or 60Co, which are sent to the surface and back kicking. Such a device is used at low altitudes of several tens of meters. The main advantage is the stability of rays into which hardly affect interference. Such an altimeter was set on a spaceship "Soyuz" and the product designated as "Cactus". The system was installed on the bottom of the ship and had the appropriate labeling of radiation hazard.

As a result, it should be noted that the flight altitude is very important, since its exact definition allows to ensure flight safety. Because of this, the approach to determining the height should be comprehensive and the aircraft should have several altimeters of different designs at once. Only in this way can the accuracy of the calculation be achieved. The crew of the aircraft undergo deep training in working with instruments, which allows analyzing all the readings of the system. The failure of one of the instruments of height during the flight is equivalent to a flight incident. 

A great thing is the equipment.


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