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Kinds of Horizontal Angles
The kinds of horizontal angles most commonly measured in surveying are:
 Interior angles;
 Angles to the right;
 Deflection angles.
Interior Angles
They are measured on the inside of a closed polygon. Normally the angle at the
apex with in a polygon is measured. Then a check can be made on their value
because the sum of all angles equals (n-2)180. Polygons (closed traverse)
commonly used for boundary surveys.

Fig. 2.3 Interior angles of a polygon

Note: Exterior angles are located outside a closed polygon and they provide a
0
check, i.e. the sum of interior and exterior angles at any station must total 360 .

Angles To The Right
Angles may be determined by clockwise measurement from the preceding to
the following line. Such angles are called angles to the right or azimuths from the
back line.

Fig. 2.4 Angles to the right

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