Introduction: Surveying

Introduction: Surveying | Civil Engineering SSC JE (Technical) - Civil Engineering (CE) PDF Download

Introduction - SURVEYING

Surveying is the process of determining relative positions of different objects on the surface of the earth by measuring horizontal distances between them and preparing a map to any suitable scale. Measurements are taken in a horizontal plane.

The primary aims of field surveying are:

• to measure the horizontal distance between points
• to measure the vertical elevation between points
• to find out relative direction of lines by measuring horizontal angles with reference to any arbitrary direction
• to find out absolute direction by measuring horizontal angles with reference to a fixed direction

Question for Introduction: Surveying
Try yourself:
Which of the following is NOT a primary aim of field surveying?

Reconnaissance:

•This is an exhaustive preliminary survey of the land to be surveyed. It may be either ground reconnaissance or aerial reconnaissance survey.
• Reconnaissance is made on arrival to site during which an overall picture or view of the area is obtained. The most suitable position of stations is selected, the purpose of the survey and the accuracy required will be drawn, and finally, the method of observation will be established.

Objectives of reconnaissance:
1. To ascertain the possibility of building or constructing route or track through the area.
2. To choose the best one or more routes and record on a map
3. To estimate probable cost and draft a report.

Principle of working from whole to part:
-It is a fundamental rule to always work from the whole to the part. This implies a      precise control surveying as the first consideration followed by subsidiary detail     surveying.

-This surveying principle involves laying down an overall system of stations whose positions are fixed to a fairly high degree of accuracy as control, and then the survey of details between the control points may be added on the frame by less elaborate methods.
-Once the overall size has been determined, the smaller areas can be surveyed in the knowledge that they must (and will if care is taken) put into the confines of the main overall frame.
-Errors which may inevitably arise are then contained within the framework of the control points and can be adjusted to it.

The surveying may primarily be divided into two divisions :
1. Plane surveying
2. Geodetic surveying
1. Plane surveying : The surveys in which earth surface is assumed as a plane and the curvature of the earth is ignored, are known as plane surveys.

2. Geodetic surveying : The surveys in which curvature of the earth is taken into account and higher degree of accuracy in linear as well as angular observations is achieved, are known as Geodetic surveying.

Classification based on Instrument used :
(1) Chain surveying
(2) Compass surveying
(3) Plane table surveying
(4) Theodolite surveying
(5) Tacheometric surveying
(6) Triangulation surveying
(7) Aerial surveying
(8) Photogrammetric surveying

MAP : The representation of the earth surface on a small scale, is called a map.

Question for Introduction: Surveying
Try yourself:
What is the objective of reconnaissance in surveying?

Units of Measurement, : There are two kinds of measurements used in plane surveying:
1. Linear measurement i.e. horizontal or vertical distances.
2. Angular measure i.e. horizontal or vertical angles.
-Scales on the maps are represented by the following two methods:
(i) Numerical scales
(ii) Graphical scales
(a) Engineer’s scale
(b) Fractional scale

(a) Engineer’s scale : The scale on which one cm on the plan represents some whole number of metres in the ground, is known as Engineer’s scale, e.g., 1 cm = 5 m, 1 cm = 10 m etc.

(b) Fractional scale : The scale on which an unit of length on the plan represents some number of the same unit of length on the ground is known as frictional scale, e.g , 1:500. 1:1000, 1:5000 etc.
Scales

Scale is the fixed ratio that every distance on the plan bears with corresponding distance on the ground.

Representative Fraction (RF)

Classification of Scales : The scales drawn on the maps or plans, may be classified as:
(i) Plain scale
(ii) Diagonal scale
(iii) Scale of chords
(iv) Vernier scale
-Plain Scale : A plane scale is one on which it is possible to measure only two dimensions, i.e. metres and decimetre, kilometres and hectametres, miles and furlongs etc.

Plain scales as Recommended by IS 1481-1959
Full size – 1 : 1
50 cm to a metre – 1 : 2
40 cm to a metre – 1 : 2.5
20 cm to a metre – 1 : 5
10 cm to a metre – 1 : 10 
-A useful map scale should be sufficiently long and should not be less than 19 cm and more than 32 cm.

(i) Diagonal scales : On a diagonal scale, it is possible to measure three dimensions such as kilometres, hectametres and decametres; or yards, feet and inches etc.

(ii) Vernier scales : It consists of two approximating scales, one of them is fixed and is called the primary scale, the other is movable and is called the vernier.

Least count of a vernier is equal to the difference between the smallest division on the vernier scale.
-Least count (L-C) =
-1 hectares = 10, 000 m2
-If 1 cm = 50 m, then R.F.

Error Due to Use of the Wrong Scale

1. Correct Length

2. Correct Length

Error Due to Incorrect Length of Chain or Type

(a) True length of the line, (l)

Here, L = Designated length of tape/chain
L’ = Actual but wrong length of the chain or tape
l’ = Wrong measured length of the line
l = Actual true length of the line

Case (a): In case of Area

where, A = True area
A’ = Wrong measured area

Case (b): In case of volume

where, V = True volume
V' = Wrong measured volume

The document Introduction: Surveying | Civil Engineering SSC JE (Technical) - Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Civil Engineering SSC JE (Technical).
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FAQs on Introduction: Surveying - Civil Engineering SSC JE (Technical) - Civil Engineering (CE)

 1. What is surveying?
Ans. Surveying is the technique of determining the relative position of points on the earth's surface. It involves measuring distances, angles, and elevations to create maps and plans for construction or land use.
 2. What is reconnaissance in surveying?
Ans. Reconnaissance is the initial stage of surveying that involves gathering information about the area to be surveyed. This includes studying maps, aerial photographs, and existing survey records. It helps to identify potential problems and plan the survey accordingly.
 3. What are the different types of surveying techniques?
Ans. There are different types of surveying techniques such as plane surveying, geodetic surveying, topographic surveying, construction surveying, and hydrographic surveying. Each technique is used for a specific purpose and involves different tools and methods.
 4. What are the tools used in surveying?
Ans. The tools used in surveying include measuring tapes, theodolites, total stations, GPS receivers, and levels. These tools help to measure distances, angles, and elevations accurately.
 5. Why is surveying important in civil engineering?
Ans. Surveying is a critical part of civil engineering as it helps in designing, planning, and constructing various structures such as buildings, roads, bridges, and dams. It ensures that the construction is done in the right place, at the right level, and with the correct dimensions. Accurate surveying is crucial for ensuring the safety and integrity of the structure.

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