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to remove parallax – усувати паралакс;
collimation error – колімаційна помилка;
it is required to check – необхідно перевірити;
within acceptable limits – в допустимих межах.

Task 2. Read and translate the following text.

Text 1 Levelling

Levelling and surveying methods are widely used for different

kinds of measurements. Accurate levelling is a particularly important
part of site establishment, installation and quality assurance.
Levelling is one of the types of geodetic measurements used to

create a geodetic elevation reference grid and to conduct topographic
surveying, as well as to plan, construct, and maintain engineering
structures, railroads, highways, and so on. The results of leveling are
used in research on the figure of the Earth, variations in the levels of

seas and oceans, and vertical movements of the Earth’s crust. Several
types of leveling are distinguished, based on the method used:
geometric, trigonometric, barometric, mechanical, and hydrostatic.

Levelling is extremely important for engineering surveying,
which involves the measurement of three quantities: heights, angles
and distances.
Levelling is widely known as the process of measuring heights. It

is possible when levelling to measure heights with an accuracy of
millimeters. Heights can also be measured using such instruments as:
total stations, handheld lasers and GPS devices. However, levelling

offers an inexpensive, simple and accurate method for measuring
heights, and it is widely used in construction sites.
Heights are defined using horizontal and vertical lines. For site

work, any horizontal line can be chosen as a datum for heights and for
levelling. The height of a point is measured along the vertical above or
below the chosen datum. The height of a point relative to a datum is

known as its reduced level (RL).
On most construction sites there is a permanent datum. The
horizontal line or surface passing through this, with its height,
becomes the levelling datum. The height of the datum can be

arbitrary, a value often used for this is 100.000m. This is chosen to
avoid any negative heights occurring.
Any reference point on site which has had a height assigned to it

is known as a bench mark. For most surveys and construction work,
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