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Altitude
Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum (geodesy), datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometry, geographical survey, sport, or atmospheric pressure). Although the term ''altitude'' is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage. In aviation, altitude is typically measured relative to mean sea level or above ground level to ensure safe navigation and flight operations. In geometry and geographical surveys, altitude helps create accurate topographic maps and understand the terrain's elevation. For high-altitude trekking and sports, knowing and adapting to altitude is vital for performance and safety. Higher altitudes mean reduced oxygen levels, which can lead to altitude sickness if proper acclimatization measures are not taken. Vertical distance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flight Level
In aviation, a flight level (FL) is an aircraft's altitude as determined by a pressure altimeter using the International Standard Atmosphere. It is expressed in hundreds of feet or metres. The altimeter setting used is the ISA sea level pressure of 1013 hPa or 29.92 inHg. The actual surface pressure will vary from this at different locations and times. Therefore, by using a standard pressure setting, every aircraft has the same altimeter setting, and vertical clearance can be maintained during cruise flight. Background Flight levels are used to ensure safe vertical separation between aircraft. Historically, altitude has been measured using an altimeter, essentially a calibrated barometer. An altimeter measures ambient air pressure, which decreases with increasing altitude following the barometric formula. It displays the corresponding altitude. If aircraft altimeters were not calibrated consistently, then two aircraft could be flying at the same altitude even thou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth's Atmosphere
The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes), all retained by Earth's gravity. The atmosphere serves as a protective buffer between the Earth's surface and outer space, shields the surface from most meteoroids and ultraviolet solar radiation, keeps it warm and reduces diurnal temperature variation (temperature extremes between day and night) through heat retention (greenhouse effect), redistributes heat and moisture among different regions via air currents, and provides the chemical and climate conditions allowing life to exist and evolve on Earth. By mole fraction (i.e., by quantity of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other trace gases (see Composition below ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Density Altitude
The density altitude is the altitude relative to standard atmospheric conditions at which the air density would be equal to the indicated air density at the place of observation. In other words, the density altitude is the air density given as a height above mean sea level. The density altitude can also be considered to be the pressure altitude adjusted for a non-standard temperature. Both an increase in the temperature and a decrease in the atmospheric pressure, and, to a much lesser degree, an increase in the humidity, will cause an increase in the density altitude. In hot and humid conditions, the density altitude at a particular location may be significantly higher than the true altitude. In aviation, the density altitude is used to assess an aircraft's aerodynamic performance under certain weather conditions. The lift generated by the aircraft's airfoils, and the relation between its indicated airspeed (IAS) and its true airspeed (TAS), are also subject to air-density ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kármán Line
The Kármán line (or von Kármán line ) is a conventional definition of the Outer space#Boundary, edge of space; it is widely but not universally accepted. The international record-keeping body Fédération Aéronautique Internationale, FAI (Fédération aéronautique internationale) defines the Kármán line at an altitude of above above mean sea level, mean sea level. While named after Theodore von Kármán, who calculated a theoretical limit of altitude for aeroplane flight at above Earth, the later established Kármán line is more general and has no distinct physical significance, in that there is a rather gradual difference between the characteristics of the atmosphere at the line, and experts disagree on defining a distinct boundary where the atmosphere ends and space begins. It lies well above the altitude reachable by conventional airplanes or high-altitude balloons, and is approximately where satellites, even on very eccentric trajectories, will Orbital decay, dec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Standard Atmosphere
The International Standard Atmosphere (ISA) is a static atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations. It has been established to provide a common reference for temperature and pressure and consists of tables of values at various altitudes, plus some formulas by which those values were derived. The International Organization for Standardization (ISO) publishes the ISA as an international standard, ISO 2533:1975.International Organization for Standardization, Standard Atmosphere', ISO 2533:1975, 1975. Other standards organizations, such as the International Civil Aviation Organization (ICAO) and the United States Government, publish extensions or subsets of the same atmospheric model under their own standards-making authority. Description The ISA mathematical model divides the atmosphere into layers with an assumed linear distribution of absolute temperature ''T'' against ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Troposphere
The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the planetary surface of the Earth, the average height of the troposphere is in the tropics; in the middle latitudes; and in the high latitudes of the polar regions in winter; thus the average height of the troposphere is . The term ''troposphere'' derives from the Greek words ''tropos'' (rotating) and ''sphere, sphaira'' (sphere) indicating that rotational turbulence mixes the layers of air and so determines the structure and the phenomena of the troposphere. The rotational friction of the troposphere against the planetary surface affects the flow of the air, and so forms the planetary boundary layer (PBL) that varies in height from hundreds of meters up to . The measures of the PBL vary according to the latitude, the landform, and the t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pressure Altitude
Given an atmospheric pressure measurement, the pressure altitude is the imputed altitude that the International Standard Atmosphere (ISA) model predicts to have the same pressure as the observed value. The National Oceanic and Atmospheric Administration (NOAA) published the following formula for directly converting atmospheric pressure in millibars (mb) to pressure altitude in feet (ft): h = 145366.45 \left 1 - \left( \frac \right)^ \right In aviation, pressure altitude is the height above a standard datum plane (SDP), which is a theoretical level where the weight of the atmosphere is as measured by a barometer.Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B), 2016, Chapter 4, p 4-4 It indicates altitude obtained when an altimeter is set to an agreed baseline pressure under certain circumstances in which the aircraft’s altimeter would be unable to give a useful altitude readout. Examples would be landing at a high altitude or near sea level under conditions of e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Pressure
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The Standard atmosphere (unit), standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013.25 Bar (unit), millibars, 760millimetre of mercury, mm Hg, 29.9212inch of mercury, inchesHg, or 14.696pounds per square inch, psi.International Civil Aviation Organization. ''Manual of the International Standard Atmosphere, ICAO Standard Atmosphere'', Doc 7488-CD, Third Edition, 1993. . The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth; that is, the Earth's atmospheric pressure at sea level is approximately 1 atm. In most circumstances, atmospheric pressure is closely approximated by the fluid pressure, hydrostatic pressure caused by the weight of Earth's atmosphere, air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so atmospher ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mean Sea Level Pressure
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013.25 millibars, 760 mm Hg, 29.9212 inchesHg, or 14.696psi.International Civil Aviation Organization. ''Manual of the ICAO Standard Atmosphere'', Doc 7488-CD, Third Edition, 1993. . The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth; that is, the Earth's atmospheric pressure at sea level is approximately 1 atm. In most circumstances, atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so atmospheric pressure decreases with increasing elevation. Because the atmosphere is thin relative to the Earth's radius—especially the dense atmospheric layer at low altitudes� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Pressure
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013.25 millibars, 760 mm Hg, 29.9212 inchesHg, or 14.696 psi.International Civil Aviation Organization. ''Manual of the ICAO Standard Atmosphere'', Doc 7488-CD, Third Edition, 1993. . The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth; that is, the Earth's atmospheric pressure at sea level is approximately 1 atm. In most circumstances, atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so atmospheric pressure decreases with increasing elevation. Because the atmosphere is thin relative to the Earth's radius—especially the dense atmospheric layer at low altitu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
