The document describes the main components of a transit theodolite. It lists 12 key components: 1) trivet, 2) foot screws, 3) tri branch, 4) leveling head, 5) spindles, 6) lower plate, 7) upper plate, 8) A frame, 9) T frame, 10) altitude bubble, 11) compass, and 12) tripod. The lower plate measures horizontal angles with graduations from 0 to 360 degrees. The upper plate has two verniers used to read fractions of degrees on the lower plate. The tripod supports the theodolite during field use.
4. INTRODUCTION
Theodolite is a basic surveying
instrument which is use for measuring
vertical and horizontal angle.
Theodolite is more precise than
magnetic compass.
Magnetic compass measures the angle
up to as accuracy of 30’. However a
vernier theodolite measures the angles
up to and accuracy of 10’’, 20”
5.
6. Definition
A transit theodolite is one in which the
telescope can be revolved through a
complete revolution about its
horizontal axis in a vertical plane.
7. Main Components of Transit Theodolite
1. Trivet
2. Foot Screws
3. Tri Branch
4. Leveling Head
5. Spindles
6. Lower Plate
7. Upper plate
8. A Frame
9. T Frame
10. Altitude Bubble
11. Compass
12. Tripod
8. 1. Trivet
It is a circular plate having a
central, threaded hole for
fixing the theodolite on
tripod stand.
It is also called the base line.
9. 2. Foot Screws
Lower part – The Trivet
Upper Part – It is passes
through the threaded hole in
the tribrach plate.
Foot screws is used for
leveling the instrument.
10. 3.Tri Branch
The upper parallel triangular plate carrying three foot
screws at its ends is called the Tri branch.
4.Levelling Head.
It is consists of two parallel plates separated by the 3
leveling screws.
11. It gives support the upper
part of the instrumental and
attaches it to the tripod
12. 5. Spindles & Clamp
1. Inner spindle
2. Outer Spindles
The inner axis is solid and conical and the outer spindle
is hollow.
13. 6. Lower Plate
an annular horizontal plate with the graduations provided
all around, from 0 to 360°, in a clockwise direction. The
graduations are in degree divided in to 3 parts so that each
division equals to 20 min.
Horizontal angles are measured with this plate.
The size of the theodolite is defined by the diameter of
horizontal circle.
14. 7. Upper plate
Horizontal plate of smaller diameter provided with two
venires. on diametrically opposite parts of its
circumference.
They are used to read fractions of the horizontal circle
plate graduations.
The venires are graduated in 20 min and each minute is
divided in 3 to 5 parts making least count 20” or 10”.
15. 8.‘A’ Frame or Standard
Two frames are provided on the
upper plate to support the
telescope, the vertical circle and
vertical vernier scale.
These frame are known as
standard or A-frame.
16. 9. T Frame or Index bar
It consists of a vertical leg known as clipping arm and a
horizontal bar called the index arm engraved with
venires C and D at its ends..
It is used as seat for altitude bubble and also provides
vernier reading for vertical angle measurement
17. 10. Altitude Bubble
A sensitive level tube called altitude bubble, is attached to
the top of the T- frame.
This bubble is brought to the center by the clip screw.
A mirror is provided on the top of bubble.
18. 11. Compass
Sometimes a circular box compass is mounted on the
vernier scale between the standards.
It is provided for taking the magnetic bearing(W.C.B) of
line
19. 12. Tripod
The theodolite is mounted on a
strong tripod when being used in the
field.
The legs of the tripod are solid or
framed. At the lower ends of the
legs, pointed steel shoes are
provided to get them pushed into
ground.
The tripod head has male screws on
which the trivet of the leveling head
is screwed.