Topcon DL-103 Series, Instruction Manual

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18
Measuring a Horizontal Angle
This instrument has a horizontal circle which can be used to measure
horizontal angles. The horizontal circle is graduated in 1
°
(1g) divisions
and is numbered every 10
°
(10g), with the scale calibrated from 0
°
to
350
°
(0 to 390g). The angular value increases as the instrument is
revolved clockwise.
1
First, set up and level the instrument over the starting point, point C.
Then sight through the telescope on the backsight, point A. Align the
rod on point A precisely to the vertical cross-hair using the horizontal
tangent screw. Rotate the horizontal circle ring until zero is set on the
scale.
2
Next, sight through the telescope on the rod held on point B and pre-
cisely align with the horizontal tangent screw. The angular reading
will be the horizontal angle between points A and B from point C, the
angle ACB.
Horizontal circle
Point A
Point B
Point C
Horizontal angle: 30
°
or 33g
Degree type
Point A
Point B
10
0
350 40 30 20
Point A Point B
10
0 40 30
20 3 9 0
Grade type