B.sc. agri i foswce unit 2 leveling

leveling

1. Leveling Course: B.Sc. Agricultural Subject : Fundamental of Soil, Water and Conservation engineering Unit: 2

2. Definitions used in levelling Level surface:-It is the surface parallel to the mean spheroidal surface of the earth Level line:-Line lying on level surface. Horizontal plane:-Horizontal plane through a point is a plane tangential to level surface. Horizontal line:-It is a straight line tangential to level line.

3. Datum:-“It is an arbitrary level surface from which elevation of points may be referred”. In India mean sea level is considered as datum of zero elevation it is situated at Karachi. Mean sea level is the average height of sea for all stages of tides it is derived by averaging the hourly tide height over a period of 19 years. Elevation or Reduced level:-It is height or depth of any point above or below any datum. It is denoted as R.L.

4. Bench Mark (B.M.):-It is a fixed reference point of known elevation with respect to datum. Line of collimation:-It is a line joining the intersection of cross hairs of diaphragm to the optical centre of object glass and its continuation. It is also known as line of sight. Height of instrument:-It is the elevation of line of collimation with respect to datum Back sight:-It is a staff reading taken at a known elevation. It is the first staff reading taken after setup of instrument.

5. Fore sight( F.S.):-It is the last staff reading taken denoting the shifting of the instrument. Intermediate sight.(I.S.):-It is staff reading taken on a point whose elevation is to be determined. All staff reading between B.S. and F.S. are Intermediate sight. Change Point:-It is a point on which both fore and back sight are taken.

6. Leveling may be the art of determining the relative heights or elevations of points are objects on the earth’s surface. It deals with measurements in a vertical plane. Leveling

7. The height of instrument (H. L): It is the elevation (or the R.L.) of the plane of collimation (or plane of sight) when the instrument is correctly leveled. It is also called the height of plane of the collimation. To determine elevation of points instruments are required, viz. A level Leveling staff or rod. The level Level consists of essentially Leveling head The limb Telescope bubble tube

8. Dumpy level y level / wye level Tilting level/Coke’s reversible level Automatic level Types of level

9. Dumpy level The Dumpy level is a simple, compact and stable instrument. The telescope is rigidly fixed to its supports. Hence it cannot be rotated about horizontal axis. 1

10. Wye level The essential difference between wye level and other levels is that in wye level the telescope is carried by two vertical wye supports. The telescope can be rotated, moved or even raised in wyes. 2

11. Tilting level It is also known as I.O.P. Level (Indian office Pattern). In this level the telescope tilts about its horizontal axis hence it is called tilting level 3

12. Automatic level It is also known as self aligning level. It is a recent development. The fundamental difference between auto level and other levels is that the levelling is not manually but it is levelled automatically. It is achieved by inclination compensating device. 5 4

13. Levelling Staffs Levelling staffs are scales on which these distances are measured. Levelling staffs are of two types A. Self reading staff B. Target staff

14. A. Self reading staff The self reading staff can be read directly by the level man looking through the telescope. Common types of self reading staffs Ordinary staff Folding Staff

15. A vernier is provided on target to give precise reading. In target staff level man directs the staff man to move the target up and down until it bisects by the line of sight. The staff man observe the staff reading B. Target staff For very precise works and sight target staff are used. A movable target is provided in this staff. 6

16. Bench Marks Bench mark is a point of known elevation There are 4 kinds of bench marks 1. GTS (Great trigonometrically survey bench mark) 2. Permanent bench mark 3. Arbitrary bench mark 4. Temporary bench mark

17. 1. GTS Bench mark They are the bench marks established with very high degree of precision at regular intervals by the survey Department of India all over the country Their position and R.Ls values above mean seal level at Karachi are given in catalogue formed by the department. Mean sea level 7

18. 2. Permanent Bench mark Permanent benchmarks are fixed in between GTS benchmarks by govt. agencies such as railways, PWD, etc. This bench marks are written on permanent objects such as milestones, culverts, bridges etc. their value are clearly written and their position are recorded for future reference 8

19. 3. Arbitrary bench marks:- These are reference points whose R.L.s are arbitrarily assumed. They are used in small works such bench mark may be assumed as 100 or 50 m

20. 4. Temporary bench marks:- They are the reference points established during the leveling operations when there is a break in work, or at the end of day’s work the value of reduced levels are marked on some permanent objects such as stones, trees etc.

21. TYPES OF LEVELING EQUIPMENT Hand Levels Abney Levels Automatic Levels Laser Levels Dumpy Levels

22. HAND LEVELS A hand held instrument. Low precision work or for checking purposes. ABNEY LEVELS A type of hand level. Includes a clinometers for measuring vertical angles. AUTOMATIC LEVELS Incorporate a self leveling feature. Popular for general use. Easy to set up and use. Rough leveling is done by adjusting the leveling screws, then the self-leveling feature takes over to completely level the telescope. 9

23. LASER LEVELS Used in construction surveys to create a visible line of known orientation and elevation from which measurements for line and grade can be made. Give accurate readings at distances of 1000 ft. Can provide control elevations over a 1,000,000 square foot area from a single setup. DUMPY LEVELS Standard equipment before automatic levels were available. The telescopic sight must be completely leveled manually by adjusting the leveling screws. 10

24. Level Instrument Automated Levels Easy to use (not power!) Needs experience Robust even in hostile environment Digital Levels Push-button technique No reading errors, special staff Readings are stored and analyzed digitally 11

25. Automated Levels (Compensator) Pendulum Bull Eye Tribrach 12

26. Digital Levels Uses Barcode staffs Internal storage of data Download to the computer Automated height computation + adjustment No feeling for quality anymore You frequently need power plugs 13 14

27. Tripod Wooden design or aluminum 15

28. Staff/Pole Wood, aluminum INVAR type for high precision leveling 16

29. Change Plate For long survey lines Allows change of instruments Best is a metal change plate Screws e.g. at fences Sharp stones or nails 17

30. Bubble Keep the pole upright Any tilt will disturb your readings 18 19

31. Survey Markers Gives you a fixed point Should be of good quality Should be long-term Preferable in bedrock, settled buildings, or bridges Do not use fences or walls 20

32. 1. Classification of leveling 1. Simple levelling 2. Differential leveling 3. Fly levelling 4. Check levelling 5. Profile levelling 6. Cross levelling 7. Reciprocal levelling 8. Precise levelling 9.Trignometric levelling 10. Barometric levelling 11. Hypersometric levelling

33. 1. Simple leveling:- It is the simplest method used, when it is required to find the difference in elevation between 2 points. 21

34. 2. Different leveling: It is the operation of leveling to determine the elevations of points. Some distance a part or to establish bench marks. This method is used to find the difference in the elevation between points if they are too far apart or the difference in elevation between them is too much . 22

35. 3. Fly leveling:- Fly leveling is just like differential leveling carried out to check the accuracy of leveling work. In fly leveling only B.S. and F.S. are taken. 23

36. 4. Check leveling: It is the operation of running levels for the purpose of checking the series of levels, which have been previously fixed. At the end of each day’s work, a line of level is run, returning to the starting point of that day with a view to check the work done on that day. This kind of leveling is carried out to check the accuracy of work. It is done at the end of the days work in the form of fly leveling to connect the finishing point and starting point.

37. 5. Profile leveling or L-Section : It is the operation in which the object is to determine the elevation of points at known distance apart along a given line, and thus to obtain the accurate out line of the surface of the ground. It is called the longitudinal leveling or sectioning. This method is used for taking levels along the centre line of any alignment like road, railway canal etc. The object is to determine the undulations of the ground surface along the alignment

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39. 6. Cross sectioning: It is the operation of leveling to determine the surface undulation or outline of the ground transverse to the given line and on either side of it. This operation is carried out perpendicular to alignment at an interval of 10, 20 ,30, 40 m. The idea is to make an estimate of earthwork.

40. 7. Precise leveling:- It is used for establishing bench marks for future public use. It is carried out with high degree of accuracy using advanced instruments 8. Trigonometric leveling: It is then process of leveling in which the elevations of points are computed from the vertical, angles and horizontal distance measured in the field. In this method vertical distances between points are computed by observing horizontal distances and vertical angle between points.

41. 9. Barometric leveling: It is the method of leveling in which the altitudes of points are determined by means of a barometer, which measures atmospheric pressure. In this method the altitude difference is determined by means of a barometer.

42. 11. Reciprocal leveling: It is then method of leveling in which the difference in elevation between two points, accurately determined by two sets of observation when it is not possible to set up the level midway between the two points. This method is adopted to accurately determine the difference of level between two points which are far a part. It is also used when it is not possible to setup level in midway between two points

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44. Text book and web sources www.agriinfo.in ecourses.iasri.res.in Soil erosion and Conservation by R. P. Tripathi and H. P. Singh

45. Thanks