Text 9

1. Read and translate the text:

Surveying

Surveying is a means of relatively large-scale, accurate measurement of Earth surfaces. It includes the determination of the measurement data, the reduction and interpretation of the data to usable form, and the establishment of relative position and size according to given measurement requirements.

Surveying has two similar but opposite functions:

1. The determination of existing relative horizontal and vertical position;

2. The establishment of marks to control construction or to indicate land boundaries.

For many centuries surveying has been an essential element in the development of the human environment.

Surveying is divided into the categories of plane surveying and geodetic surveying. Plane surveying concentrates on mapping relatively small areas (smaller than 12 miles (20 km) across), where the curvature of the Earth is not a significant factor, the calculations of plane trigonometry are sufficient.

Geodetic surveying covers large areas of the globe with the attendant corrections of the curvature of the earth. Such surveying must be very accurate, and geodetic instruments are precise.

Measurements made in the direction of gravity are designated as vertical, and measurements made perpendicular to the direction of gravity are designated as horizontal.

Surveying measurements are of four types:

1. horizontal lengths of distances;

2. vertical lengths or differences in height or elevation;

3. horizontal angles measured in horizontal planes;

4. vertical angles measured in vertical planes.

Horizontal lengths are generally measured in short, straight sections that together form short arc along the Earth’s surface. With a surveyor’s level the difference in height between two points can be determined. Directions are given in azimuths or bearings.

Land-areas surveys are made to determine the relative horizontal and vertical position of topographic features and to establish reference marks to guide construction or to indicate land boundaries. Reconnaissance of the area is followed by a preliminary survey. A map and then a plan are prepared based on this kind of survey. Surveys to establish property boundaries involve a thorough knowledge of real-estate laws as well as skills in survey techniques.

Surveys of water-covered areas determine the horizontal coordinates of points on the surface of the body of water (position fixing) and the water’s depth at those points. Position fixing requires that measurements are to be made both on land and on water.

2. Answer the following questions:

1. What is surveying?

2. What does surveying include?

3. What are the functions of surveying?

4. What are the main categories of surveying?

5. What are the main types of measurements in surveying?

6. How are horizontal lengths measured?

7. What are land surveys made for?

8. What do surveys involve? Why?

9. What is the difference between vertical and horizontal measurements?

10. How can you define the difference in height between two points?

3. Decide, whether the sentences are true or false:

1. Surveying is a means of relatively small-scale, accurate measurement of Earth surfaces.

2. Surveying includes only the determination of the measurement data.

3. For many centuries surveying has been an essential element in the development of the human environment.

4. Plane surveying concentrates on mapping relatively small areas.

5. Geodetic surveying covers also small areas of the globe with the attendant corrections of the curvature of the earth.

6. There are four types of surveying measurements.

7. Horizontal lengths are generally measured in long, curved sections that together form short arc along the Earth’s surface.

8. Directions are given in azimuths or bearings.

9. Land-areas surveys are made to determine the relative horizontal and vertical position of topographic features and to establish reference marks to guide construction or to indicate land boundaries.

10. Position fixing requires that measurements are to be made only on land.