CiIvil Surveying - Fundamentals and Chain Surveying
INTRODUCTION AND CHAIN SURVEYING
1. Define Surveying. What are the fundamental principles of surveying?
Surveying is an art of determining the relative positions of various points on, above or below the surface of the earth by means of direct or indirect measurement of distance, direction and elevation.
The principles of surveying are:
(i). Working from whole to part.
(ii). To locate a new station by at least two measurements (angular, linear) from fixed reference points.
2. What is the object or purpose of surveying?
The primary object of surveying is to prepare a plan or map to show the relative position of the objects on the surface of the earth. It is also used to determine the areas, volumes and other related quantities.
3. Name the different ways of classification of surveys.
(i). Plane surveying
(ii). Geodetic surveying. b. Secondary classification
(i). Based on instruments used (ii). Based on methods.
(iii). Based on object
(iv). Based on nature of the field
4. Differentiate between plane and geodetic surveying.
The curvature of the earth is neglected.
A line joining any two points is considered straight.
The triangle formed by any three points is considered as plane triangle.
It is done on a area less than 250 Km 2
The curvature of the earth is taken.
A line joining any two points is considered as curved line.
The triangle formed by any three points is considered as spherical triangle.
It is done on a area greater than 250 Km 2
5. Classify surveying based on the equipments.
1 Chain surveying
2 Compass surveying
3 Plane table surveying
4 Theodolite surveying
5 Tacheometric surveying
6 Photogram metric surveying
7 Aerial surveying
6 Explain the constructions of a diagonal scale.
For a given short length ( PQ=PR), draw a right angle triangle. Its base( PR) and height (PQ) are equal. A short length is divided into a number of parts by using the principle of similar triangles in which like sides are proportional.
1-1 represents 1/ 10 PQ
9-9 represents 9/ 10 PQ
7. Define chain surveying. What is the fundamental principle of chain surveying?
Chain surveying is the type of surveying in which only linear measurements are made in the field.
The main principle of chain surveying or chain triangulation is to provide a framework consist of number of well-conditioned triangles or nearly equilateral triangles. It is used to find the area of the field.
8. What is a well-conditioned triangle? What is its specific advantage?
A triangle is said to be well- conditioned or well proportioned when it contains no angle smaller than 300 and no angle greater than 1200 .
The main principle of chain surveying is chain triangulation. It consists of frame work of triangles. To plot the network of triangles accurately, the triangles must be nearly equal to equilateral or well-conditioned. The distortion due to errors in measurement and plotting should be minimum.
9. What are the operations involved in chain survey?
(i). Ranging: The process of locating intermediate points on a straight line between two end points in a straight line.
(ii). Chaining: The process of measuring the distance with a chain or tape.
(iii). Offsetting: The process of measuring the lateral distance of the object from the survey line to the left or right according to their positions.
10. What are the instruments required for a chain survey?
Chain or tape, Arrows, Pegs, Ranging rods, Offset rods, Laths or whites, Plumb bob, Cross staff and Mallet.
11. Write the different types of Chain.
(i). Metric chain
(ii). Non-Metric chain
(a).Gunter’s chain or Surveyor’s chain
(b). Engineer’s chain
(c). Revenue chain
(d). Steel band.
1. Differentiate between Gunter’s chain and Engineer’s Chain
Gunter’s chain or Surveyor’s chain
It is 66 feet long and divided in to 100 links. 1link = 0.66 feet
Measurements are in miles and furlongs.
It is 100 feet long and divided in to 100 links. 1link = 1 feet
Measurements are in feet and decimals
13. Define: (a).Main stations.
Main station is a prominent point on the chain line and can be either at the beginning of the chain line or at the end or along the boundary.
(b). Subsidiary stations:
The stations located on the main survey lines are known as Subsidiary
(c). Tie stations:
These are also subsidiary stations taken on the main survey lines to locate the details of the object.
14. Distinguish between a check line and a tie line.
Check lines or Proof lines are the lines which are run in the field to check the accuracy of the work
The length of the check line measured in the field must agree with its length of the plan.
The main object of running a tie line is to take the details of the objects.
Tie line is a line which joints subsidiary stations or tie stations on the main line.
15. What are the instruments used for setting out right angles to a chain line?
(i). Cross staff.
a. Open cross staff
b. French cross staff
c. Adjustable cross staff (ii). Optical square.
(iii). Prism square (iv). Site square.
16. What are offsets? Classify them.
An offset is the lateral distance of an object or ground feature measured from a survey line. The two types of offsets are,
(i). Perpendicular offset: The angle of offset from a point on a chain line is 900.
Oblique offset: When the angle of offset is other than 900 .
17. What is the use of a line Ranger?
The line Ranger is a small reflecting instrument used for fixing intermediate points on the chain lines. Without going to either end, we can fix the intermediate points.
18. What are the stages of fieldwork in chain surveying? Or What are the steps involved in chain survey?
1. Reconnaissance: It is the preliminary inspection of the area to be surveyed.
2. Marking and fixing Survey lines.
3. Running survey lines.
4. Taking Offsets.
19. What are the different tape corrections?
1. Correction for absolute length or standardisation.
2. Correction for temperature.
3. Correction for pull or tension.
4. Correction for sag. (- ve)
5. Correction for slope. (- ve)
20. What are the errors in chaining?
(i). Compensating Errors: Which are liable to occur in either direction and tend to compensate.
(ii). Cumulative Errors: Which occur in the same direction and tend to add or subtract. It may be positive (measured lengths more than the actual length) or negative (measured lengths less than the actual length).
21. What are the different sources of errors in chain surveying?
(i). Instrumental errors: incorrect length of the chain (Cumulative Errors).
(ii). Personal error: Bad ranging (Cumulative Errors). Careless holding (Compensating Errors). Bad straightening (Cumulative Errors). Non- horizontality (Cumulative Errors). Sag in chain (Cumulative Errors). Miscounting and misreading and booking.
(ii). Natural Errors: Variation in temperature. (Cumulative Errors).
22. Enumerate the instruments used for measurement of lengths of survey lines.
(i). Chain or tape. (ii). Passometer. (iii). Pedometer (iv). Odometer