Do you know how altitude is calculated?If you're curious about these questions, let's take a look at them.
Altitude, in simple terms, is how high a place is from sea level. However, sea level is not static, it fluctuates with factors such as the Earth's rotation, tides, air pressure, etc. So, we can't use sea level directly to calculate altitude, but we need to use a stable reference plane, which is mean sea level. Mean sea level is an ideal level based on long-term observations, averaging sea level fluctuations. Different countries have different mean sea levels, such as China's Yellow Sea mean sea level, the United States' North American vertical datum, etc. These mean sea levels are used to define the elevation system of the respective country, that is, to calculate the altitude.
So, how do we measure the distance from a place to mean sea level?This involves a number of different measurement methods, such as: triangulation: this is a method of using the properties of triangles to calculate the vertical height by measuring the horizontal distance and angle on the ground. This method is suitable for areas with relatively flat terrain, but in areas with complex terrain, it will be affected by occlusion and errors.
Barometric pressure measurement: This is a method that uses the law of atmospheric pressure with altitude to measure the barometric pressure and reverse the vertical height. This method is suitable for areas with complex terrain, but it needs to consider the influence of temperature, humidity, wind speed and other factors.
Satellite surveying: This is a method that uses satellite positioning technology to calculate the three-dimensional coordinates of any point on the ground by receiving satellite signals, so as to obtain the vertical height. The advantage of this method is high accuracy and wide coverage, but it requires specialized equipment and data processing.
Gravity measurement: This is a method that uses the law of gravity field with height to measure gravity and reverse the vertical height. The advantage of this method is that it is not affected by meteorological conditions, but it needs to take into account the shape of the earth, the gravitational field, the movement of the earth's crust, and other factors.
I hope the above answers will be helpful to you.