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A vertical angle is an angle formed by two connected lines in the
vertical plane, that is, between a low point and two higher points.
A vertical angle BAC can be formed, for example, by the line of
sight AB from station A on a river bank to a higher water-pump

installation, and the line of sight AC from station A to a much higher
water-storage tank.
Whenever a line is not horizontal, it has a slope. The slope can be

uphill or downhill. Its steepness depends on the difference in height
between its points. The slope of the ground affects the measurement of
distances.
The slope of a line is called the gradient. It may be defined as:

 The change in vertical distance or elevation over a given
horizontal distance, or the change in horizontal distance over a given
vertical distance;

 The vertical angle, made by the sloping line and a horizontal
line.
Modern Vertical angle and slope measurement methods are as

follows:
Accurac
Section 1 Method 2 Remarks Equipment
y

Quick and rough

estimate for rather Home-
Clinometer,
4.1*,4.2* Low steep slopes. made
models 1 & 2
Hand-held clinometer
instrument.

Is fixed in ground. Home-
Clinometer, Low to
4.3* Direct reading in made
model 3 medium
percent. clinometer

Is fixed in ground.
Home-
Clinometer, Low to Small, easy to make.
4.4* made
model 4 medium Direct reading in
clinometer
percent.

Low Quick and rough
(about estimate. Lyra-
4.5** Clisimeter
10 Direct reading in clisimeter

percent) percent.

Optical
4.6** Optical Medium Quick, rather good
clinometer
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