Text 2

1. Read and translate the text:

Alexander Ross Clarke

A.R.Clarke (1828 – 1914) was an English geodesist whose calculations of the size and shape of the Earth were the first to approximate accepted modern values with respect to both polar flattening and equatorial radius. The figures from his second determination (1866) became a standard reference for U.S. geodesy, even after the acceptance of other figures by the International Union of Geodesy and Geophysics in 1924.

Appointed to the Royal Engineers (1847), Clarke remained with the British ordnance survey at Southampton from 1850 to 1881. He was responsible for the principal triangulation (long-distance trigonometric surveying) of the British Isles and published the results of the first geodetic survey of Great Britain in 1861. Entrusted with comparing the standards of length for measuring an international arc of triangulation from Ireland to Russia, he published his results in 1866. His Geodesy (1880) has remained one of the best textbooks on the subject.

2. Find information about other Russian and foreign geodesists. Get ready to tell this information in the classroom. Use in your speech different general formulas such as:

They say…

First of all…

To begin with…

In my opinion…

To my mind…

As to me…

Talking of…

Apparently…

Obviously…

Evidently…

Generally speaking…

Practically speaking…

In fact …

As far as I know…

As far as I remember…

The matter is that …

I want to press the point…

On the one hand…

On the other hand…

Above all…

All in all…

Summing it up …

Text 3

1. Read and translate the text:

Methods of Geodesy

Until the advent of satellites, all geodesic work was based on land surveys made by methods employing a geodesic coordinate system.

Triangulation in navigation, surveying, and civil engineering, is a technique for precise determination of distances and angles for location of a ship’s or aircraft’s position, and in such attempts as road building, tunnel alignment, and other construction. It is based on the laws of plane trigonometry, that if one side and two angles are known, the other two sides and angle can be readily calculated. One side of the selected triangle is measured. This is the baseline. The two adjacent angles are measured by means of a surveying device known as a theodolite, and the entire triangle is established. By constructing a series of such triangles, each adjacent to at least one other, values can be obtained for distances and angles not otherwise measurable. Triangulation points are usually placed on the tops of the hills because the neighbouring points must be clearly visible.

Triangulation was used by the ancient Egyptians, Greeks, and other peoples at a very early date, with crude sighting devices that were improved into the diopter (an early theodolite) in the 1^st century AD by Hero of Alexandria.

Trilateration is a method of surveying in which the lengths of the sides of a triangle are measured, usually by electronic means, and from this information, angles are computed. By constructing a series of triangles, adjacent to one another, a surveyor can obtain other distances and angles. Formerly, trilateration was little used in comparison to triangulation, because of the difficulty of the computations involved. But the development of electronic distance-measuring devices has made trilateration a common and preferred system.

2. Answer the questions:

1. What was all geodesic work based until the advent of satellites on?

2. What are the main geodetic methods used nowadays?

3. What is the main principle of triangulation?

4. When and where was triangulation introduced?

5. Where are usually triangulation points placed on? Why?

6. What is the main idea of trilateration?

7. How can a surveyor obtain distances and angles using this method?

3. Complete the sentences:

1. Triangulation is a technique for...

2. Triangulation is based on the laws of plane trigonometry, that if...

3. Triangulation points are usually placed on the …

4. Triangulation was used by …

5. Trilateration is a method of ...

6. A surveyor can obtain other distances and angles by …

7. Trilateration was little used in comparison to triangulation, because …

8. … has made trilateration a common system.