Absolute call height of any given object above sea level. In Russia and in some other European countries the zero mark of the Kronstadt tide gage is taken for the initial point of calculation of average values. In relation to it the average long-term value of level of Baltic from which heights on the land are counted is calculated.
It is required to you
- - physical map of the area;
- - GPS navigator;
- - level;
- - lath.
Instruction
1. Consider the physical map. The land on it is painted in different colors - green, light brown, red-brown. In its lower part there is a scale of heights, too multi-colored. On the card you can notice also the closed lines with figures - horizontals. They are drawn in brown or black color.
2. Find a point necessary to you. It is possible to identify it by the name of the next large object or on coordinates. Look in what color the site of the card on which point necessary to you is located is painted. Find the same color on a scale of heights. In the same place you will find numerical designation of height corresponding to this shade.
3. It is possible to determine height above sea level and by horizontals. The top part of the figures written on them is directed towards increase in a relief. Calculate a relief step. It is the difference between the next horizontals, in this case - between what there is the necessary point.
4. Put indicators of horizontals and halve. If the point is not strictly in the middle, determine its absolute height by interpolation. On interpolation in geodesy the creation of intermediate horizontals is applied. It is possible to make it by means of a palette.
5. It is possible to determine the absolute height of the area in several ways. The GPS navigator gives its quite exact value, and it is rather simple to look at the screen. However it is possible to carry out also leveling of a surface on the known mark applied on the geodetic sign. It represents a metal pipe or a core on which end the horizontal plate is welded on. The sign is buried to the earth on this plate.
6. Find the geodetic sign using the map. Its height is defined and plotted. From this platform carry out leveling up or vny to a required point. If the point is above the platform, put an optical or digital level on it. The digital device allows to define at once and distance between points, and a corner between an initial horizontal and a required point.
7. Imagine a triangle at which the hypotenuse and one of corners are known. According to the theorem of sine calculate a leg which will represent distance from a required point to its projection to the known horizontal. Having added the size of this leg to a geodetic mark, you also receive the absolute height of a point necessary to you.