Horizontal origin
Different sea areas have different sea levels. For example, the sea level on the Pacific side of the Panama Canal is 20 cm higher than the sea level on the Atlantic side.
Mainland China: The average sea level of the Yellow Sea calculated from the long-term observation data of the Qingdao Port tide gauge station is used as the base level (zero-elevation level).
Taiwan, China: Set the "Taiwan Horizontal Origin" on the east bank of Keelung Port as the measurement reference point.
Japan: Taking the average sea surface of Tokyo Bay as the benchmark, the actual measurement datum point is located at the "Japanese horizontal origin" of the Land Survey Department/Front Court of the Congressional Headquarters of the Old Staff Headquarters, Chiyoda Ward, Tokyo.
United Kingdom: The average sea surface "OrdnanceDatumNewlyn" in Newlyn, Cornwall, on the southwest coast of England from May 1915 to April 1921.
Netherlands: Amsterdam's average sea surface "NormaalAmsterdamsPeil".
Special altitude
The highest elevation on the surface of the earth: Mount Everest (8848.86 meters)
The lowest elevation on the surface of the earth: Dead Sea (-416 meters) )
The lowest place on earth: Mariana Trench (-11034 meters)
The lowest altitude country: Netherlands (average altitude of -11 meters)
The highest altitude country in the world: Lesotho (located in southern Africa is a small country with beautiful mountains and rivers and unique scenery) (average altitude above 1000 meters)
High altitude areas
The surface of the earth (or The higher altitude area in the atmosphere is called high altitude area. High altitude is sometimes defined as 2400 meters (8000 feet) above sea level.
At high altitudes, atmospheric pressure is lower than sea level. This is due to two competing physical effects: gravity, which makes the air as close to the ground as possible; the heat of the air makes the molecules rebound and expand each other.
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