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Task 2. Read and translate the following text.

Text 1. Errors and their sources

When properly defined, "error" pertains only to measurement –
that is, to estimating anything where exactness is not possible. It isn’t
applied to counts, where exactness is possible. Errors are unavoidable
even for the most thoroughly trained and motivated measurer. They

occur to some extent in virtually every measurement because of
imperfections of instruments and people, as well as influences of the
natural environment.

There are four general types of errors in surveying: natural,
instrumental, personal and calculation errors.
Natural errors. Measurements are usually made in an

environment that is essentially uncontrollable (outdoors). Effects on
instruments and processes from such factors as temperature,
atmospheric pressure, atmospheric refraction, humidity, solar and

other heat, wind, gravity, and Earth’s curvature must be measured, and
readings must be corrected for these variables if accurate results are to
be expected.
Instrumental errors. All measurements employ instruments,

from the simple plumb line to the most sophisticated electronic
apparatus. Some error is always present in the measurements due to
imperfection in manufacture, adjustment or basic characteristics of the

instrument.
Personal errors. Since humans are directly involved with all
measurements, and since humans are imperfect, errors are inevitable
in measurements. Automation and electronics have reduced personal

errors in measurements, but not eliminated them. People still perform
centering and alignment judgments, for example, even when readings
are digital.

Calculation errors. Unless sufficient digits are recorded and
carried through all computation steps, and unless conversion factors
and constants contain sufficient digits, round-off errors occur.

Significant figures in measurements directly affect the significant
figures in computed results.
Personal errors are nearly all random in nature. People cannot

perceive anything with exactness. In surveying, this refers to the
alignment of cross-hairs on targets, centering of instruments over
ground points, reading rods and scales, centering level bubbles, etc.

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