Surveying Unit 1 - Chain Surveying .pptx

Chain Surveying

1. SEMESTER:III Department: Civil Engineering Course Code: 19CECN1303 Course Name: Surveying By S. Krishnakumar, Assistant Professor

2. Course Outcomes The course is intended to: Calculate the areas and included angles based on the concepts of Chain, Compass and Plane table surveying Determine the reduced levels various points and areas & Volumes of the earth surface. Compute the heights and distances of various objects using Theodolite Determine the elevation and distances using tacheometric principles Compute the various elements of curves for setting out. 19CECN1303 - Surveying

3. General Objective of course To understand the basic concept of surveying Apply the surveying concept and equipments in real life You should be able to use a set of tools to solve the problems in an optimal way You should be able to understand the pitfalls (sources of error) to avoid them 19CECN1303 - Surveying

4. CO1 - Calculate the areas and included angles based on the concepts of Chain, Compass and Plane table surveying LO1: Explain the principles and types of surveying SO1: Define Surveying w.r.t the relative positions SO2: List Principles of Surveying SO3: Explain the Importance of Working from whole to part in surveying SO4: List the types of Surveying SO5: Compare the types of surveying 19CECN1303 - Surveying

5. 19CECN1303 - Surveying Any near by landmarks??

6. SO1: Define Surveying w.r.t the relative positions Definition of surveying B. C. Punmia Surveying may be defined as the art and science of determining the relative position, in three dimensions, of natural and man-made features on or beneath the surface of the Earth by measurements of horizontal and vertical distances, angles and directions. These features may then be represented in analog form as a contoured map, plan or chart, or in digital form as a three dimensional mathematical model stored in the computer. 19CECN1303 - Surveying Duggal

7. Discussion about Importance of surveying Objectives of surveying Types of surveying Classifications of surveying Principles of surveying Surveying measurements 19CECN1303 - Surveying

8. Objects of survey Plan: When the area is surveyed is small and the scale to which its result plotted is large, then it is known as plan. Scale : 1:100,1:200,1:500 ,etc. E.g.: a plan of a building 19CECN1303 - Surveying

9. Map: When the area surveyed is large and the scale to which its result plotted is small, then it is known as Map Scale : 1:10000,1:100000,etc E.g. : Map of India Objects of survey 19CECN1303 - Surveying

10. 1.2 Types of Surveying There are two types of surveying: Plane surveying Geodetic surveying 19CECN1303 - Surveying

11. Plane surveying The surveying in which earth surface is assumed as a plane and the curvature of the earth is ignored is known as plane surveying . As the plane survey extends only over small areas, the line connecting 2 points is considered as a straight line and the angle b/t any 2 lines is considered as plane angle . 19CECN1303 - Surveying

12. Geodetic surveying The surface of the earth is not plane but spheroidal. Therefore, the line connecting any two points on the earth’s surface is not a straight line but a curve . The surveying in which curvature of the earth is taken into account for all measurements is known as geodetic survey. It possess a high degree of accuracy . It is also called trignometrical surveying. 19CECN1303 - Surveying

13. Classifications of surveys 1. Based upon the nature of the field 2. Based upon the method 3. Based upon the instruments used 4. Based upon the objective of survey 19CECN1303 - Surveying

14. 1.Based on the nature/ place of survey Land survey –city survey,engg survey, topographic ,cadastral survey Hydrographic survey Under – ground survey Aerial survey 19CECN1303 - Surveying

15. 2.Based on the method Triangulation survey Traverse survey Closed Open traverse traverse 19CECN1303 - Surveying

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18. 3. Based on the instruments used Chain survey Compass survey Plane table survey Theodolite survey Tacheometric survey Total Station GPS 19CECN1303 - Surveying

19. Instruments… Levelling Staff Digital level Tilting Level Telescope is fixed cannot be tilted or moved Dumpy Level Telescope can be tilted slightly about its horizontal axis with the help of tilting screw. The line of collimation is made horizontal for each observation with the help of tilting screw Instrument can be levelled automatically within a certain tilt range 19CECN1303 - Surveying

20. Levelling staff 19CECN1303 - Surveying

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22. 4. Based on the purpose/objects of survey Engineering survey Defence survey Geological survey Mine survey Geographical survey Archeological survey Route survey 19CECN1303 - Surveying

23. Application of surveying in civil Engineering The planning and design of all Civil Engineering projects such as construction of highways, bridges, tunnels, dams etc are based upon surveying measurements. Project of any magnitude is constructed along the lines and points established by surveying. Thus, surveying is a basic requirement for all Civil Engineering projects. Other principal works in which surveying is primarily utilized are •  to fix the national and state boundaries; •  to chart coastlines, navigable streams and lakes; •  to establish control points •  to execute hydrographic and oceanographic charting and mapping; and •  to prepare topographic map of land surface of the earth. 19CECN1303 - Surveying

24. Principle of surveying Working from whole to part: to localize the errors and to control the accumulation of errors. Establish primary control points with high precision Establish secondary and tertiary control points within the system boundary and form triangle/rectangle may be with less precision. This will help in localizing the error and to control the propagation of error. 19CECN1303 - Surveying

25. Working from whole to part 19CECN1303 - Surveying

26. Working from whole to part This is being achieved by establishing a hierarchy of networks of control points . The less precise networks are established within the higher precise network and thus restrict the errors. To minimize the error limit, highest precise network (primary network) figure 1.1 of control points are established using the most accurate / precise instruments for collection of data and rigorous methods of analysis are employed to find network parameters. This also involves most skilled manpower and costly resources which are rare and cost intensive. 19CECN1303 - Surveying

27. Working from whole to part 19CECN1303 - Surveying

28. The purpose of working from whole to part is To localize the errors and To control the accumulation of errors. 19CECN1303 - Surveying

29. Fixing new points by at least ‘2’ independent process The reference of any point, say X, has to kept with respect to, at least, two permanent objects or well defined points, say Y and Z. Generally, this has been achieved by taking measurement of two parameters. The location of a point, say X can be done as shown in the figure below. (a) Distances YX and ZX ( Figure 1.2 ) 19CECN1303 - Surveying

30. (b) Perpendicular distance OX and distance OY or OZ ( Figure 1.3 ) 19CECN1303 - Surveying

31. (c) Distance YX or ZX and angle YZX or ZYX ( Figure 1.4(a) )and ( Figure 1.4(b) ) 19CECN1303 - Surveying

32. (d) Angles YZX and ZYX. ( Figure 1.5 ) The point of intersection of the two measured parameters defines the position of the point. 19CECN1303 - Surveying

33. Measurements of distances Direct method –tapes ,chains Computative method – tachometry, triangulation, etc 19CECN1303 - Surveying

34. Instruments used in chain surveying Instruments for Measuring Horizontal Distance 1) Chain or tape 2) Arrows Instruments for Marking Stations on the Ground 3) Ranging rods 4) Cross staff 5) Offset rods 6) Pegs 7) Plumb bob 8)Field book 19CECN1303 - Surveying

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36. DESCRIPTION a) Chain: The chain is composed of 100 or 150 pieces of galvanized mild steel wire , 4mm in diameter called links . The ends of each link are bent into a loop and connected together by means of three oval rings. The ends of the chain are provided with handles for dragging the chain on the ground, each wire with a swivel joint so that the chain can be turned without twisting. The length of the chain is measured from the outside of one handle to the outside of another handle. Tallies are fixed at every five-meter length and brass rings are provided at every meter length except where tallies are attached 19CECN1303 - Surveying

37. Types of chain Following are the various types of chain in common use: 1) Metric chains 2) Gunter’s chain or surveyors chain 3) Engineers chain 4) Revenue chain 5) Steel band or Band chain 19CECN1303 - Surveying

38. Merits and demerits of a chain It is often preferred for rough use and for ordinary works It can be read easily Due to its heavy weight , the chain is often subjected to sagging which leads accuracy of measurements 19CECN1303 - Surveying

39. 2. Arrows: Arrows are made of good quality hardened steel wire of 4 mm diameter. The arrows are made 400 mm in length, are pointed at one and the other end is bent into a loop or circle 19CECN1303 - Surveying

40. 3. Ranging rods: Ranging rods are used for marking the positions of stations and for ranging the survey lines . The length of the ranging rod is either 2m or 3m long with a heavy iron point 150 mm long at the lower end. Ranging rods are divided into equal parts 0.2m long and they are painted alternately black and white or red and white or red, white and black. 19CECN1303 - Surveying

41. 4. Cross staff: The simplest instrument used for setting out a right angle. The common forms of cross staff are: Open cross staff, French cross staff, Adjustable cross staff 19CECN1303 - Surveying

42. 5. OFFSET ROD: The offset rod is used for measuring the off set of short lengths. It is similar to a ranging rod and is usually of 3m lengths . 19CECN1303 - Surveying

43. 6. PEGS : These are rods made from hard timber and tapered at one end, generally 25mm or 30mm square and 150mm long wooden pegs are used to mark the position of the station on. 7 . PLUMB BOB: While chaining along sloping ground, a plumb bob is required to transfer the points to the ground. 19CECN1303 - Surveying

44. Principle of chain surveying The principle of chain surveying is to divide the area into a number of triangles of suitable sides . A network of triangles is preferred here as triangle is the simple plane geometrical figure which can be plotted with the lengths of its sides alone. In this case, there is no need for measuring angles 19CECN1303 - Surveying

45. Suitability of chain surveying It is suitable when the ground is fairly level and open with simple details. When large scale plans are needed , this type suitable It is suitable when the area to be surveyed is comparatively small in extent It is suitable for ordinary works as its length alerts due to continued uses Sagging of chain due to its heavy weight reduces the accuracy of measurements It can be read easily and repaired in the field itself It is suitable for rough usage 19CECN1303 - Surveying

46. Unsuitability of chain survey It is unsuitable for large areas crowded with many details It is unsuitable for wooded areas and undulating areas 19CECN1303 - Surveying

47. Technical terms Main station : It is point in chain survey where the two sides of a traverse or triangle meet (A,B,C etc ) Subsidiary station: It is a station on the survey line joining two main stations ( a,b,c , etc ) Main survey line A line joining two main stations is called main survey line ( AB,BC,etc ). B A b c C D E G d F a well 19CECN1303 - Surveying

48. Tie line The line joining two subsidiary stations is known as tie line (ac,cd,etc) and it is otherwise called subsidiary line Base line It is the longest main survey line and passing through the centre of the area . Check line This line is very much essential to check the accuracy of the field work .(ad) Technical terms 19CECN1303 - Surveying

49. Offset The perpendicular (or) the oblique distance of the object from the survey line is called an offset . Technical terms 19CECN1303 - Surveying

50. Taping: Corrections Erroneous Tape Length Slope Tension Temperature Sag Once a line is being measured, it is necessary to convert the measured length into a horizontal length. Series corrections have to be applied. Five possible corrections have to be considered. These are 19CECN1303 - Surveying

51. Taping: Corrections For synthetic tapes, only Erroneous Tape Length and slope corrections will be applied The best accuracy that can be achieved is the order of 1:1000 When using steel tapes, if only Erroneous Tape Length and slope corrections are considered, the best possible accuracy that can be obtained in the range 1:5000 If tension and temperature are added into consideration, accuracy can be increased to better than 1:10000 ~ 1: 20000 Sag only applies if tape is supported only at ends 19CECN1303 - Surveying

52. Erroneous Tape Length tape has a nominal length under certain conditions, a tape stretches with time. standardisation needs to be carried out frequently by using reference tape or baseline. standardisation length (actual tape length) nominal length (assumed tape length) 19CECN1303 - Surveying

53. For a 30m Nominal Length Tape Tape used When comparing to a standard tape, the tape used indeed has a length For every 30m measurement, the small elongated amount should be added for correction. 30 m + ∆ l 19CECN1303 - Surveying

54. Slope Correction All plan distances are always quoted as horizontal distances L, therefore any distance not measured on the horizontal will need to be corrected for slope. Slope correction must ALWAYS be considered, and either eliminated in the field or mathematically compensated. Angle may be measured by Theodolites 19CECN1303 - Surveying

55. Tension Correction A tape is a given length when pulled with a certain tension. If the tension changes then so does the tape length. Standardisation tension Modulus of Elasticity of tape material For steel, E = 200,000 N/mm 2 Cross section Area Tension applied 19CECN1303 - Surveying

56. Temperature Correction Most materials expand and contract with temperature change, and this effects taped distances. If a tape has stretched due to heat it will read shorter than it would at its normal (or standard) temperature. Length error due to Temperature change Measured length Coefficient of linear expansion Temperature change 19CECN1303 - Surveying

57. Sag Correction If the tape cannot be supported for its length then it will hang freely under the influence of gravity. The shape of the tape will take is known as ( sag ) and can be determined mathematically. Tension applied to the ends Angle of slope Weight of tape per unit length 19CECN1303 - Surveying

58. Combined Errors Actual length is: Steel Taping: Examples 19CECN1303 - Surveying

59. horizontal length AB = 29.872-0.0050+0.0139-0.0022-0.0611+0.0052 = 29.823m 19CECN1303 - Surveying

60. A steel tape of nominal length 30 m was used to measure a line AB by suspending it between supports. The following measurements were recorded Line Length Measured Slope Angle Mean Temp. Tension AB 29.872 m 3 o 40’ 5 o C 120 N The standardisation length of the tape against a reference tape was known to be 30.014 m at 20 o C and 50 N . If the tape weighs 0.17 N/m and has a cross sectional area of 2 mm 2 , calculate the horizontal length of AB. 19CECN1303 - Surveying