Surveying (Part-2) (General Engineering) (SSC JE)

Least count–The smallest magnitude which can be accurately measured using any measuring instrument is called as least count.
Least count = Smaller division / Total division

The part of surveying which deals with the measurement in the vertical plane is known as levelling.

Bearing–The angle of survey line from magnetic north direction or any fixed point or line is called as bearing.

Chaining–Measurement of survey lines with the help of chain or tape is termed as chaining.

GPS–Global positioning system that is widely used navigation system that provides precise location and timing related information worldwide. It consists of a network of satellites to collect information.

Kinematic chain–A combination of kinematic pair joints in such a way that one link is fixed and other link move relatively.

Number of pairs–
2P = l + 4
l = 2P – 4

where,
l = No. of link
P = No. of kinematic pair

Extension line–The line that project from an object for the express purpose of locating a dimension is known as extension line.

The effect of tachometer feedback in a control system is to reduce time constant and increases the gain of system and damping.

Pitot tube– It is used for measuring the velocity of flowing fluid.

Theodolite–For measuring horizontal and vertical angles and taking staff reading.

Clinometer–Used for vertical angle measurement.

Chain–It is used for linear measurement.

Levels–It is used for levelling.

Line ranger–It is a small reflecting instrument used for fixing intermediate points on the chain lines.

Clinometer–For vertical angle measurement.

• When checking flatness a straight edge can be used. They are bars with one edge that is extremely flat and are available in steel, cast iron or granite.
• Single ended straight edge can be used to determine flatness by applying it is different placed in different direction on the tested surface.
(ii) Straight edges types–
(a) Tool maker straight edge
(b) Wide edge straight edge
(c) Angle straight edge

Usually, the size of a theodolite is represented by the size of the scale plate or lower plate, i.e., a 10 cm theodolite or 12 cm theodolite etc.
1. Inner axis
2. Outer axis
3. Casing
4. PAD
5. Lower clamp screw
6. Tangent Screw
7. LUG on Levelling Head
8. Antagonising spring
• The theodolite is the most precise instrument designed for the measurement of horizontal and vertical angles.