What Is an Altimeter?
An altimeter is an instrument used to measure altitude.
There are three methods for measuring altitude. Among them, the barometric altimeter, which measures altitude based on atmospheric pressure, is predominantly used. Even in small aircraft and training planes, only barometric altimeters are installed.
As atmospheric pressure fluctuates with time and location, it is necessary to calibrate the altimeter using the latest information. Caution is needed in areas where atmospheric pressure drops, such as mountainous regions.
The remaining two types of altimeters are the radio altimeter and GPS. The radio altimeter relies on a transmitting antenna and a receiving antenna attached to the underside of the aircraft. Radio waves are sent from the aircraft to the ground, bouncing back to the receiving antenna.
Uses of Altimeter
Altimeters are used to measure the altitude of aircraft and spacecraft. Pilots of aircraft need to constantly be aware of their current altitude, making altimeters highly valuable.
While the barometric altimeter is always in use, the radio altimeter cannot be used when the distance from the ground is too great. Therefore, it is frequently employed during takeoff and landing or when flying at low altitudes, especially in poor visibility conditions.
Aircraft are generally considered to fly well at altitudes around 10,000 meters. This figure varies depending on weather conditions and factors like engine combustion and air resistance. Altimeters play a significant role in maintaining an altitude of around 10,000 meters.
Principles of Altimeter
The altimeters used in aircraft are the radio altimeter and barometric altimeter. The radio altimeter uses radio waves to measure the time it takes for reflections from a target, displaying the distance. The barometric altimeter measures atmospheric pressure, converting it into altitude for display.
For mountaineering altimeters, the barometric altimeter is commonly used. When combined with a compass and a map, it helps determine the current location, aiding in pacing during mountain climbs. The altimeter also serves as a barometer, reading changes in atmospheric pressure to confirm weather patterns.
If the atmospheric pressure rises from the evening to the next morning, the weather is expected to improve, while a descent in pressure indicates worsening weather conditions.
Structure of Altimeter
Altimeters can be classified into analog and digital types.
1. Analog Type
It measures altitude using an aneroid barometer that senses pressure. It is simple in functionality, user-friendly, and easy to maintain. There are solar-powered altimeters available, eliminating the need for battery replacement. However, caution is required as the needle may move with slight vibrations.
2. Digital Type
It offers higher accuracy compared to analog types, suitable for quickly obtaining detailed numerical values. It utilizes the piezoresistive effect, where electrical resistance changes with pressure, and is therefore called a piezoresistive altimeter. Digital altimeters often include weather and temperature prediction features, providing comprehensive preparedness. However, most digital altimeters are battery-powered, requiring attention to battery levels.
Types of Altimeter
For mountaineering altimeters, there are primarily three types: handheld, wristwatch, and app-based.
1. Handheld
Various types can be used as a compass or map. They are compact, ensuring ample space in your belongings, and size considerations are minimal. Altimeters that can be taped to the car interior are particularly suitable for driving. Adjustable altimeters with screws allow for accurate altitude measurements.
2. Wristwatch
Always worn, reducing the risk of loss, and there is no need to retrieve it from a bag. Many wristwatch altimeters are waterproof. Recently, altimeters with solar charging functions and those capable of measuring heart rates have also been introduced.
3. App-based
Apps with altimeter functionalities have been developed. This means that carrying only a smartphone enables you to accomplish almost everything. However, attention is required for battery levels and sufficient storage.
How to choose an Altimeter
Altimeters come with various features depending on the intended use. For mountaineering, waterproof and compass features are crucial. Additionally, having temperature, GPS, and solar charging functions adds an extra layer of assurance.