Falling of the river call the difference of heights between two of its points between which distance is known to the researcher. It can be defined both for all river, and for its certain site. It is necessary to know this parameter for construction of dams and locks, for drawing up maps of any given area and also to calculate a river bias. It is possible to calculate full or its partial falling.
It is required to you
- - topographic map;
- - level;
- - 2 laths 1 m long;
- - 2 laths 0.5 m long;
- - 1 lath 2 m long;
- - pencil and paper.
Instruction
1. Determine full falling of the river by the topographic map. Find on it marks of absolute height of a source and the mouth. The source always is above the mouth even if it is about the flat quiet river. On the topographic map the horizontals corresponding to the absolute height of this site are always designated. On horizontals marks are put down. It is possible to determine the direction of a bias by them, the bottom of figure is directed towards decrease in the area. If the source or the mouth of the river are not on the line of a horizontal, take an approximate mark. In geodesy and cartography the interpolation "approximately" when the average mark between those that are put down on horizontals undertakes is sometimes applied. Such way quite suits for a school task. Take away the absolute height of the mouth from the absolute height of a source. It will also be full falling of the river.
2. For definition of falling on the certain site find the large-scale map. Find on it the point, top on a current, with which it is necessary to begin measurement. Define the lower point where the measurement will come to an end. Find these points on the area.
3. Measurements require a level. The professional laser, digital or optical tool is optional to such experiment. The simplest device which the mankind used throughout many centuries can be made. Take 2 laths with a section of 5х2 cm. One of them, 0.5 m long, fastens strictly perpendicular to the end another. The design in the form of letter T has to be formed. At the same time the general height equals strictly 1 m. By means of a nail or a screw attach thread with a plumb to the middle of a half-meter lath. Its length not less half a meter. From a nail down a long lath draw a straight line for exact establishment of a vertical on a plumb. It is useful to hammer also in the lower point of this line a small nail for exact aiming into a plumb edge. Make all faces of laths flat. 2 such levels are necessary.
4. Make a lath with divisions. They have to correspond on length of the required measurement accuracy. Vykraste a lath on divisions in the alternating strips of red and white color. It will facilitate work on the area.
5. In the top basic point put the end of a lath in water that it reached a bottom. It is necessary to do it in shallow water that water level was accurately visible against the background of a lath. The first level has to be pritselen on a horizontal level accurately in that point of a lath where the water surface concerns it. At the same time it is established strictly vertically on a plumb. The participant of an experiment changes a lath for the second level and establishes it below on a current, aiming the top level at the basis of the first device. After that it remains on the place, and that who has the first level goes down below on a current and aims at the basis of the second. So, alternating, researchers carry out leveling to the lower point of measurement specified on the card. At the same time it is necessary to keep count of the established levels.
6. If in a final point of measurement it is impossible to establish a level on all height, then the lath is put to the penultimate device and aiming is made in one of divisions that is considered at final settlements. As height of each level is equal to exactly 1 m, the difference of heights in meters turns out equal to the whole quantity of levels plus or minus of the amendment on penultimate laths. It is also falling of the river on this site.