The article will discuss what height is - absolute and relative. Height is a term used in geography. An example will show the differences between these two concepts. After reading the article, you will have a stable concept of two types of heights in geography, and it will be easier to navigate the terrain and solve practical problems.
What is height and why is it used in geography?
Any geographical object located on the surface of the Earth has a certain set of coordinates (latitude and longitude), as well as altitude characteristics. The relief of our planet is heterogeneous, somewhere high mountains dominate, somewhere deep down go bottomless hollows and gorges. The concept of height was invented by people in order to most accurately describe certain features of the relief of the earth's surface.
In addition, the concept of height is used on topographic and high-altitude maps. The signed height allows you to display a three-dimensional relief on a flat surface of the map. As a rule, all heights are measured in meters - a standardized unit from the international system. Heights can take both positive and negative values. On the earth's surface, the range of heights ranges from -400 meters (the hollow of the Dead Sea) to 8848 meters (the highest peak in the world is Mount Everest). In order to better understand how the heights differ, it is necessary to introduce the concept of absolute and relative height.
Absolute height
The concept of absolute height is identical to the concept of height above sea level, or height above sea level. So, the absolute height of one or another point of the earth's surface represents the excess of this point over the average annual sea level in a particular system of sea heights. In Russia, all absolute heights are measured relative to the zero mark in Kronstadt, which is located at the very edge of the water in this northwestern city.
In other countries, there are other zero levels, but the essence of the concept of absolute height does not change from this. Absolute altitude is measured in meters above sea level. It can take both positive and negative values. In the figure above, the absolute height of the hill is indicated by a blue arrow. There is no strict correlation of concepts and values of absolute and relative height. The absolute height can be greater, less, or equal to relative.
Relative height
Relative height, by definition, is the excess of any two points on the earth’s surface relative to each other. It should be noted right away that, in contrast to the absolute height, the relative one always takes strictly positive values, since it numerically equals the difference of points with higher and lower absolute heights.
If you refer, for example, to the figure above, you can see that the absolute height of the hill is 5 meters, while the relative height of the same hill is already 6 meters. How did it happen? Everything is quite simple and follows from the concept of relative height. So, the authors of this figure decided to measure the relative excess of a hill (a positive landform with a positive elevation) over the basin (a negative landform with negative absolute heights). To do this, they subtracted from the absolute height of the highest point (hill, 5 m) the absolute height of the lowest point, above which they sought to exceed the hill (-1 m). According to the rule of addition and subtraction, 5 - (-1) = 6. Precisely 6 meters is the excess of the hill above the basin, and this value is equal to the absolute height.
Strictly speaking, a hill can have an infinitely large number of relative heights, it all depends on what we will measure it with respect to. As an example, we find the relative height of the highest hill (on the right) from the hill below, it is shown on the left. From the difference in the absolute heights of these positive landforms (5 meters for high and 2.5 meters for low hills), we obtain that the relative height of the largest hill from the low hill is 5-2.5 = 2.5 meters. By analogy with this example, you can find the relative heights of anything. Now you can answer the question of how to determine the absolute and relative heights.
How are relative heights measured?
Now you understand how the absolute height differs from the relative in geography. To determine the relative heights, it is convenient to use a special device - a rail. To do this, at the starting point, relative to which the excess is sought, a rail is placed. Conventionally, this point is taken as a height with a mark of 0. Next, as shown in the figure above, you need to move up a hill or mountain until you reach the height of the staff and its highest point is below the level of your legs.
Then it is necessary to fix the point on the hill, which corresponds to the position of the highest point of the staff standing at level zero, and shift the staff to this point. Thus, at the second point, the relative height will be equal to 1 height of the staff. The operation must be done until you reach the highest point on the hill. In this case, the relative height will be equal to the sum of all the heights of the rearranged rail.
Instead of a rail, you can use any object whose height is known in advance. If there is absolutely nothing at hand, the relative height can be measured by your own height by doing the manipulations described above. In addition, the relative height can easily be measured as the difference in absolute heights, if they are known in advance.
How are absolute heights measured?
Absolute height cannot be measured in this way in the field. Of course, it would have been possible, however, this would require the presence in the immediate vicinity of the sea surface. To find the absolute height, you need to use a terrain map or satellite positioning devices, in which it is possible to automatically determine the height.
Now you have a steady idea of how the absolute height and relative height differ. Good luck in solving practical geographical problems and in everyday orientation in the environment!