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LECTURE №3

MEASUREMENTS AND COMPUTATIONS

3.1 Introduction
Making measurements and subsequent computations and analyses using them
are fundamental tasks of surveyors. The process requires a combination of human
skill and mechanical equipment applied with the utmost judgment. No matter how
carefully made, however, measurements are never exact and will always contain
errors.
Surveyors, whose work must be performed to exacting standards, should
therefore thoroughly understand the different kinds of errors, their sources and
expected magnitudes under varying conditions, and their manner of propagation.
Only then can they select instruments and procedures necessary to reduce error
sizes to within tolerable limits.

3.2 Types of Measurements in Surveying
There are five basic kinds of measurements in plane surveying:
 Horizontal angles
 Horizontal distance
 Vertical angles
 Vertical distance
 Slope distance
By using combinations of these basic measurements it is possible to compute
relation positions between any points.
Measurement of distances and angles it is the essence surveying.
Angle is simply figure formed by the intersection of two lines or figures
generated by the rotation of a line about a point form an initial position to a
terminal position. The point of rotation is called the vertex of the angle.
There are several systems of angle measurement. The most common ones are
sexagesimal system and centesimal system
This system uses degrees, minutes and seconds. In this system, a complete
rotation of a line (circle) is divided in to 360 degrees of arc. One degree is divided
in to 60 minutes and 1 minute is further divided in to 60 seconds of arc. The
0
symbols for degree, minutes and seconds are , ’ and ’’ respectively.
0
E.g. 35 17’46’’
0
90 , 00’ 00’’

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