Survey.

The simplest and most commonly used method of measuring the distance between two points on the ground is called chain surveying. Angles in surveying are measured with special instruments called transit (теодолит). In its simplest form the transit is a telescope mounted above a horizontal circular scale. Route survey is a survey necessary for the location and construction of transportation or communication lines such as highways railroads, canals, transmission lines and pipe-lines. The preliminary work consists of a topographic survey. City surveying is the term frequently applied to the operation of laying out lots and to the municipal surveys made in connection with the construction of streets, water supply systems and sewers. The maps and data produced by surveyors are used by civil engineers in many ways. Before construction begins the exact position of the various parts of the dam, or the track of the railway or road, are fixed on the ground by using normal surveying methods. In choosing the site for a dam, for instance, an engineer can study on a map the courses of all the rivers and streams in the area. By reading the contours he can calculate the amount of water which can be stored by building a dam of a given height in a certain place. In the same way the results of a soil survey clearly marked on a map will give the engineer vital information about the foundations. When deciding the route of a railway or road, the gradients, radii of curves, heights of embankments and depth of cutting can be calculated from data supplied by the surveyor.

Terrestrial photo grammar or photographic surveying from ground stations had been found to be a useful addition to other methods in mapping of mountainous areas.

Дата добавления: 2015-07-25