The height chart below shows conversions from cm to feet and inches, rounded to a maximum of 2 decimal places. Alternatively, we have a range of individual calculators for height measurements that include, amongst others, cm to inches and inches to cm. If you have any suggestions or queries about this conversion tool, please contact me.
Warning: It is necessary to enable JavaScript for full calculator functionality. Sonars can be active or passive. Active sonars emit sound pulses and listen for their echoes. Passive sonars listen for the sounds made by vessels and their equipment and analyze them. They can be used to locate targets in the water. An ultrasonic rangefinder is a distance measuring device using the same principle as a sonar, only in the air. It detects a distance to an object by emitting an ultrasonic pulse, receiving a bouncing signal, and measuring the time it takes for the sound pulse to return to the rangefinder receiver.
They can measure the distance from several millimeters to several dozen meters. A stadimeter is an optical distance measuring instrument similar to a sextant used for estimating a range to an object of known height. It measures the angle between the top and the bottom of the object while it is observed from the stadimeter. A camera autofocus AF optical system is used not only to focus on an automatically or manually selected point or object but also as a distance-measuring device with the distance displayed in a focusing distance window.
Binoculars with a reticle and telescopic sights measure distances using a technique called stadiametric rangefinding. They use the same principle as a stadimeter described above. To measure the angle to a distant object of known height, they have a reticle with marks of a known angular spacing to estimate an angle to an object of know height, for example, a person or a tank.
Optical rangefinders use comparing two images obtained from two different optical systems spaced on different devices from several centimeters rangefinder cameras to several meters navy rangefinders. An operator rotates the optical prisms to achieve image coincidence and reads the distance from a dial.
A laser rangefinder is an optoelectronic device for measuring a distance from an observer to an object. It measures the time of a laser ray travel from the observer to the object and back after reflection from the object. Handheld laser rangefinders can measure distances up to 25 km. Lasers with optical telescopes were used to measure the distance between Earth and the Moon.
This technique is also used in laser altimeters. A lidar is a tool used for surveying. It measures a distance to an object by illuminating it with a laser beam and measuring the time it takes for the beam to go to the object and back to the sensor.
Lidars are used for making maps and to control autonomous cars. Like in laser rangefinders, radar altimeters and rangefinders transmit a short pulse and measure the transit time for it to hit the target object or surface, reflect from it and return back. These devices can also measure speed. Radio navigation systems use radio frequencies to determine the position of a vessel or an aircraft on the Earth.
This includes, of course, measuring the distance from a receiver to the ground station transmitter. The radio navigation systems also measure angular directions and velocity by means of measuring the Doppler shift of radio waves.
GPS technology made the majority of such systems obsolete. DME is a radio navigation equipment used by civil aircraft to measure the distance slant range between an aircraft and a DME ground station. The measurement is achieved by timing the propagation delay of radio signals between an aircraft and the ground station.
An airborne interrogator sends a signal to the ground station, which replies with its signal. This signal is received by the airborne interrogator and the distance is calculated from a known time delay and the speed of light.
DME ground equipment is usually combined with the Very high frequency omni-directional range VOR equipment, which is used by aircraft to determine its position.
Inertial navigation systems use analog or digital computers, accelerometers linear acceleration sensors , and gyroscopes angular velocity sensors to continuously determine the position, orientation, and direction of movement and speed of a ship, a submarine, an aircraft, a missile, or spacecraft without the need to use external references. Of course, such systems can also measure distance. These systems are called inertial because they work by measuring and integrating inertial forces, which are forces arising due to acceleration of the reference frame, for example, of a spacecraft.
Older inertial navigations systems used gyrostabilized platforms with many precision mechanical moving parts that could wear out and were vulnerable to gimbal lock. Newer systems do not use mechanical moving parts and their sensors are rigidly fixed to the structure of the moving object. Instead of mechanical rotating gyroscopes, ring laser gyroscopes are used. Unlike navigational systems based on radio waves from ground stations or satellites, the inertial navigation systems are immune to jamming and deception.
For example, in — GPS devices started going weird near the Kremlin showing users that they were at the center of Vnukovo airport, about 20 miles southwest of the Kremlin. Most probably this has happened because the government wanted to remove drones from the area. After all, many of them are preprogrammed to stop operating near major airports. If smartphones and drones were equipped with inertial navigation systems instead of satellite receivers, the smartphones would show the correct location and the drones would fly.
More about drones, their sensors, and navigation. In , the author of this article, for the first time in his life, observed a complete blockage of satellite navigation signals near the Livadia Palace in Crimea Russia during President Putin's visit there. A satellite navigation system uses satellites to provide positioning of a moving vehicle fitted with a receiver. Like all other navigation systems, satellite navigation systems can measure distance with great precision.
The coverage of these systems can be regional or global, the latter can be achieved by using a satellite constellation of 18—30 satellites on medium Earth orbit 19, to 23, km. Like all radio navigation systems, satellite navigation is also vulnerable and even a small pocket device can easily block very small signals from satellites.
Try doing a search , or posting to the forum. You may also be looking for a date difference or molecular weight. You can also contact us directly if you find any missing units or errors. A centimetre American spelling centimeter, symbol cm is a unit of length that is equal to one hundreth of a metre, the current SI base unit of length.
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