Theodolite is the most precise instrument used for measuring horizontal and vertical angles.
Horizontal and vertical distances can also be calculated indirectly.
(a) Transit Theodolite (or) Transit:
The Theodolite in which line of sight can be reversed by revolving the telescope through 180° in the vertical plane. Transit Theodolite is most commonly used.
(b) Non Transit Theodolite:
Either plain Theodolite or Y-Theodolite. This can not be used for most of the works.

Essential parts of a transit Theodolite:

a) Telescope: Mounted on a spindle known as horizontal axis or trunion axis. Internal focusing telescope is widely used.

b) Vertical Circle: It is circular graduated arc attached to the trunion axis of the telescope. Controlling by a vertical circle clamp and its corresponding slow motion or tangent screw.

c) Index frame or T-frame or Vernier frame: Two verniers are fitted to this to read the vertical circle. Clip screw is used for slight adjustment. Altitude bubble is placed on top of index frame.

d) Levelling head: It consists of two parallel triangular plates known tribrach plates.

e) Lower plate or scale plate: Size of a Theodolite is represented by the size of scale plate. i.e., 10cm Theodolite etc.

f) A-frame
g) Upper plate or vernier plate.
h) Plate levels
i) Tripod
j) Plumb bob
k) Compass

Note: Tangent Screw is operated for final adjustment of reading or bisection when both clamp screws tightened.

Some important Definitions and Terms:
(a) Centering: The process of setting up the instrument exactly over the station mark. Plumb bob is made use of.

(b) Vertical axis: Axis about which the instrument rotates in the horizontal plane. Also known as Azimuth axis.

(c) Horizontal axis (or) Trunion axis: Axis about which the telescope and vertical circle rotate in vertical plane.

(d) Line of sight (or) line of collimation: The line passing through the intersection of horizontal and vertical cross hairs and optical centre of object glass and its continution.

(e) Transiting: The process of turning the
telescope in vertical plane through 180°
about the trunion axis. It is also known as plunging or reversing.

(f) Axis of level tube (or) Bubble line:
A straight line tangential to the longitudinal curve of the level tube at its centre. It is horizontal when the bubble is central.

(g) Swinging the telescope: Process of turning the telescope in horizontal plane.

(h) Face left observation (FL): The observation of the angles (horizontal or Vertical), if the circle is to the left of the observer / bubble up.

(i) Face right observation (FR): If the face of vertical circle is to the right of the observer/bubble down.

(j)Telescope normal (or Direct): When the face of the vertical circle is to the left and the "bubble (of telescope) up"

(k) Telescope inverted or reversed: When the face of the vertical circle is and the "bubble down".

(l) Changing face: Operation of bringing the face of the telescope from left to right and vice versa. It is done by transitting.

(m) Double sighting or Double centering: Measurement of horizontal angle or vertical angle twice; once with the telescope in normal condition and once with the telescope in inverted condition.

Water Distribution System

Water distribution system of any city consists of pipes, valves, hydrants, meters, pumps and service reservoirs.
Pipes are further divided into mains, sub mains, branches and laterals.
Valves are used for controlling flow.
Hydrants are used for releasing water during fire breakouts.
Meters are used for measuring discharges.
Pumps are used for lifting water.
Service reservoirs are used to store treated water and mentening pressures.
Pressure required for single storey, two storey and three storey buildings are 7m, 12m and 17m respectively. Fire hydrant pressure should be maintained more than 1kg/

Size of pipe used is generally 10cm.

Distribution system involves 40 to 70% of the total cost of water supply scheme.

Gupta & Gupta in pdf format

Civil Engineering: Through Objective Type Questions
By: SP Gupta & SS Gupta
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The load calculation for a column depends on the type of load.


Self weight of the column x Number of floors
Self weight of beams per running meter
Load of walls per running meter
Total Load of slab (Dead load + Live load + Self weight)
The columns are also subjected to bending moments which have to be considered in the final design. The best way to design a good structure is to use advanced structural design software like ETABS or STAAD Pro. These tools are leagues ahead of manual methodology for structural design, and highly recommended.
In professional practice, there are some basic assumptions we use for structural loading calculations.


Self weight of Concrete is around 2400 kg per cubic meter, which is equivalent to 240 kN. Self weight of Steel is around 8000 kg per cubic meter. Even if we assume a large column size of 230 mm x 600 mm with 1% steel and 3 meters standard height, the self weight of column is around 1000 kg per floor, which is equivalent to 10 kN. So, in my calculations, I assume self weight of column to be between 10 to 15 kN per floor.


Similar calculations as above. I assume each meter of beam has dimensions of 230 mm x 450 mm excluding slab thickness. So, the self weight can be around 2.5 kN per running meter.


Density of bricks varies between 1500 to 2000 kg per cubic meter. For a 6″ thick wall of 3 meter height and a length of 1 meter, we can calculate the load per running meter to be equal to 0.150 x 1 x 3 x 2000 = 900 kg which is equivalent to 9 kN/meter. You can calculate load per running meter for any brick type using this technique.
For autoclaved, aerated concrete blocks like Aerocon or Siporex, the weight per cubic meter is between 550 to 700 kg per cubic meter. By using these blocks for construction, the wall loads per running meter can be as low as 4 kN/meter, which can result in a significant reduction in the cost of construction.


Assume the slab has a thickness of 125 mm. Now each square meter of slab would have a self weight of 0.125 x 1 x 2400 = 300 kg which is equivalent to 3 kN. Now, assume Finishing load to be 1 kN per meter and superimposed live load to be 2 kN per meter. So, we can calculate slab load to be around 6 to 7 kN per square meter.


In the end, after calculating the entire load on a column, please do not forget to add in the factor of safety. For IS 456:2000, the factor of safety is 1.5.

Simple Derivation of W=D²L/162, the Formula to Calculate Weight of Steel bars

Diameter and length of steel bars are structural requirements of a building, and they are decided based on design procedures given by IS(Indian Standard) codes. Steel bars are sold in the market in price per weight. So we need to calculate the weight of steel required to estimate cost of construction.
The formula D²L/162 is very common and used frequently to calculate the weight of steel bars. In this post, the simple derivation behind this formula is discussed. I hope you will enjoy it.

The formula to calculate the weight of steel is:

W = Weight of steel in Kg
D = Diameter of steel bars in millimeters (mm)
L= Length of steel bars in meter (m)

Derivation of the Formula:

We know that,
Volume= Cross-sectional area x Length 
Weight = Volume × Unit weight
W = A x L x ρ
A = Area = πD²/4
π (pi) = 3.14
D = Diameter of steel bar
L = Length of steel bar
ρ (Rho) = Density of steel bar = 7850 kg/m³
W = 3.14 x D²/4  x L x 7850 kg
Where D and L are in m

We generally express diameter in millimeter (mm) and length in meter (m) unit. So to make the formula more handy let's take diameter as D mm.
D mm = D/1000 m
Putting D mm value in the expansion of W,
W = 3.141 x (D/1000)²/4 x L x 7850 kg
Or, W = D²L/162 kg
D in mm
& L in m
A model paper for SSC JE is shared in this post. Click on the download link given below and get the pdf. If you are appearing for SSC JE exam, then give it a try.

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A Precise Note On Open Channel Flow

Fluid Mechanics is a very important subject in Civil Engineering, both from application and exam point of view. It has a significant weightage in almost all competitive exams. Though this subject is common to other branches also, chapter wishes weightage varies from branch to branch. For our branch Open Channel Flow (OCF) is the most important one and enjoys most portion of weightage alone. 
So we thought a really short and precise note on this chapter may be helpful for our readers, and here in this post we are going to share it in pdf format. Must download and give it a try. If you found it useful then share with friends.


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Theodolite is the most precise instrument used for measuring horizontal and vertical angles. Horizontal and vertical distances can also be...