Surveying, permanent adjustment in transit theodolite. step by step animated.

1. TWO PEG TEST and SPIRE TEST
KARTHIK N M
Asst Prof
Dept of CIVIL ENGG
CMRIT, Bangalore

2. TWO PEG TEST

3. • Desired relation:
The Line of collimation of telescope should be parallel to the
axis of the bubble tube.
• Necessity:
Once the desired relation is accomplished LOS will be
horizontal when bubble is in the centre.

4. TEST: Method 1
100 to 120m
Ø
A B
ha
hb
hb’ha’
Ø
h=ha-hb
h’=ha’-hb’
H=h+h’
2
A=H+hb’

5. Method 2
100m
Ø
A B
ha
hb
hb’
ha’
Ø
h=ha-hb
h’=ha’-hb’
Tan Ø=h-h’
AB
Ø
As the inst is in mid way difference between 2 points
will give correct difference in elevation. Even if LOS is
inclined
Xa= H-H’
AB
X DA Xb= H-H’
AB
X (DA+AB)
CD
20m

6. SPIRE TEST

7. • Desired relation:
Horizontal axis should be perpendicular to vertical axis.
• Object:
The object of the adjustment is to make the horizontal axis is
perpendicular to vertical axis so that horizontal axis is
perfectly horizontal when the instrument is levelled.
• Necessity:
If adjustment of LOS is done the LOS will move in a plane
when telescope is plunged, this ensures that this plane will be
a vertical plane.

8. TEST
A
B

9. A
B
CD