Height above mean sea level is a measure of a location's vertical distance (height, elevation or altitude) in reference to a vertical datum based on a historic mean sea level. In geodesy, it is formalized as orthometric height. The zero level varies in different countries due to different reference points and historic measurement periods. Climate change and other forces can cause sea levels and elevations to vary over time.
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👉 Height above sea level in the context of Ionosphere
The ionosphere (/aɪˈɒnəˌsfɪər/) is the ionized part of the upper atmosphere of Earth, from about 48 km (30 mi) to 965 km (600 mi) above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on Earth. Travel through this layer also impacts GPS signals, resulting in effects such as deflection in their path and delay in the arrival of the signal.
In this Dossier
- ⭐ Core Definition: Height above sea level
- 👉 Height above sea level in the context of Ionosphere
- Height above sea level in the context of Altitude
- Height above sea level in the context of Orthometric height
- Height above sea level in the context of Mount Nebo
- Height above sea level in the context of Cairn Gorm
Height above sea level in the context of Altitude
Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference 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.
Height above sea level in the context of Orthometric height
The orthometric height (symbol H) is the vertical distance along the plumb line from a point of interest to a reference surface known as the geoid, the vertical datum that approximates mean sea level. Orthometric height is one of the scientific formalizations of a layman's "height above sea level", along with other types of heights in Geodesy.
In the US, the current NAVD88 datum is tied to a defined elevation at one point rather than to any location's exact mean sea level. Orthometric heights are usually used in the US for engineering work, although dynamic height may be chosen for large-scale hydrological purposes. Heights for measured points are shown on National Geodetic Survey data sheets, data that was gathered over many decades by precise spirit leveling over thousands of miles.
Height above sea level in the context of Mount Nebo
Mount Nebo (Arabic: جَبَل نِيبُو, romanized: Jabal Nībū; Hebrew: הַר נְבוֹ, romanized: Har Nəḇō) is an elevated ridge located in Jordan, approximately 700 metres (2,300 ft) above sea level. Part of the Abarim mountain range, Mount Nebo is mentioned in the Bible as the place where Moses was granted a view of the Promised Land before his death. The view from the summit provides a panorama of the West Bank across the Jordan River valley. The city of Jericho is usually visible from the summit, as is Jerusalem on a very clear day. The biblical town of Nebo, now known as Khirbet al-Mukhayyat, is located 3.5 km (2.1 mi) away.
Height above sea level in the context of Cairn Gorm
Cairn Gorm (Scottish Gaelic: An Càrn Gorm) is a mountain in the Scottish Highlands. It is part of the Cairngorms range and wider Grampian Mountains. With a summit elevation of 1,245 m (4,085 ft) above sea level, Cairn Gorm is classed as a Munro and is the sixth-highest mountain in the British Isles. The high, broad domed summit overlooking Strathspey is one of the most readily identifiable mountains from the nearby town and regional centre of Aviemore. Although it shares its name with the Cairngorm mountains, Ben Macdui is the highest mountain in the range.
The highest official wind speed in the UK was in 1986 when a 173 mph (278 km/h) gust was recorded at Cairn Gorm.