Altimeters

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Abstract Alimeters are instruments that measure altitude or elevation objects above or below a given level. There are three types of alimeters: pressure altimeters that make use of properties of atmosphere, radio and radar altimeters that are based on electromagnetic wave propagation, and optical altimeters that use optical properties of light and lasers. All these basic altimeters find extensive applications in industry, aviation, military, navigational aids, land surveying, remote sensing, recreations, and sports. Modern barometric altimeters are manufactured mostly as integrated circuit (IC) pressure transducers. Therefore primary signal processing such as linearization, error corrections, and gain adjustment are made within the chip. Altimeters based on electromagnetic principles transmit electromagnetic energy and detects of the reflected energy from an object. An example of these altimeters is the single‐frequency radar system that broadcasts a pulsed tone signal directly downward the object and processes the returned signals with elaborate electronic circuits for high sensitivity and resolution. Altimeters based on microwave energy transmission can be used for other purposes such as imaging, scanning, mapping, oceanographic studies, and weather forecasting. Laser altimeters operate similar to the radar altimeters by processing time differences between the transmitted and received signals. Typical examples of such altimeters are the LIDAR (light detection and ranging) and the SLA (shuttle laser altimeter) and RASCAL ( ra ster sc aning a irborne l aser). A popular system that can be used as altimeter is the Global Positioning System (GPS), which constitutes 24 satellites orbiting around Earth. Each satellite transmits electromagnetic energy carrying unique codes and information. Information picked up receivers is used to determine positions of objects in three dimensions.