The "altimeter" is used to measure the height of various locations on Earth. The tool used to determine the elevation of a location is essentially a barometer. This equipment is known as a "altimeter," and it is used in airplanes by skydivers, mountaineers, and others.
The elevation of a place is also called its "height above sea level." Scientists use the term "elevation" when referring to the surface profile of a region. They use the term "slope" when discussing the angle of a hill or mountain side.
Elevation is usually measured in meters (feet) or kilometers (miles). But some places are measured in feet, miles, or both. For example, some airports have their own altitude measuring systems based on either meter or mile scales.
Some cities have buildings that show the elevation on floor tiles. These are called "ceilings" or "roofs" and they often include a map showing which floors are which height. People can look up this chart to see where they are going.
Elevations are usually given for towns and cities, but some maps also include data for counties, states, and countries. Countries with high mountains often survey their borders using these measurements. From time to time, people make maps of areas that lack an official system for measuring elevation.
The height of the barometer liquid (mercury) at sea level is 76 cm. At the North Pole, where there are no tides or other significant surface water movements, the altitude of a station is simply the height of its surroundings as measured from the floor of its base camp.
In general, altimeters work by measuring the pressure difference between two points separated by a fixed distance. Since air is a fluid, it can be thought of as flowing from areas of high pressure to low pressure. If there's no wind, then the pressure will be the same everywhere, but if there is a wind blowing, then there will be more pressure on one side of the instrument than the other. The amount by which the pressures differ is what determines the height above sea level.
An altimeter is a device that measures height, or the distance from one location to another above sea level. Altimeters are critical navigation equipment for airplane and spacecraft pilots who want to know how high they are above the Earth's surface. They provide information about where airports are located, which can help pilots avoid terrain problems during flight.
The elevation of most cities in the United States is taken from government sources such as the National Geodetic Survey. These elevations use technology to measure the altitude of points on land and ocean with great precision. The elevation is measured in terms of the distance above mean sea level (MSL).
For most locations, the elevation is available for download from various websites maintained by governments and universities. These include the U.S. Geological Survey, which is part of the Department of Interior, the National Aeronautics and Space Administration (NASA), and the European Space Agency (ESA). Other countries with large urban populations that maintain these databases include Canada, China, India, Indonesia, Israel, Japan, Malaysia, Mexico, New Zealand, Russia, Singapore, South Korea, and Thailand.
In addition to measuring altitude, many aircraft also carry GPS receivers. The FAA requires all aircraft over 15,000 feet MSL to have electronic flight bags (EFBs) that contain certain essential navigational tools.
Surveyors use an instrument called a barometer to determine the air pressure at a specific location. So, since we know the standard pressure at mean sea level, we can readily calculate the mountain's height by subtracting the two pressures. If the barometer indicates that there is more pressure over land than under water, then the hill or mountain is high enough to cause this condition; if not, then it is not.
The barometer works on the same basic principle as a blood pressure monitor. Both measure the pressure inside and outside a body cavity. The amount of pressure difference between these two places is called the blood pressure. Just as doctors use the blood pressure to diagnose illness, so too do they use maps to diagnose error in land surveying practices. If you find that a lot of surveyors are reporting hills as mountains or valleys as holes in the ground, then there is probably a problem with the data being entered into official government records.
Blood pressure monitors use either an oscillometric method or a manual method to take readings. With the oscillometric method, the size of an oscillating weight is varied to press against the skin of your arm to cause your arterial blood pressure to show up on the monitor's graph screen. This method is fairly accurate if you keep your arm still while lying down.
Elevation normally refers to the height of a point on the earth's surface, rather than the height of a point in the air. An altitude is a measurement of an object's height, which is frequently used to refer to your height above the earth (such as in an airplane or a satellite).
Elevation and altitude have similar meanings, but they are not identical. Altitude is usually measured in meters or feet, while elevation is usually measured in meters or feet above some reference point such as sea level or ground zero.
An example will help clarify the difference: If you were to stand at the base of Mount Washington in New Hampshire, you would be standing at an elevation of 940 meters (3143 feet). The top of the mountain is 1420 meters (4680 feet) away from its base! You can see that elevation describes a distance on the ground, whereas altitude describes a distance in the air.
Elevation and altitude are both important concepts in geography. They are often used interchangeably, but there is a difference between them. Elevation is used to describe a geographical feature's height above a reference point, while altitude is used to describe your actual height above the surface of the earth.