Control surveying

Surveying

1. UNIT I 1 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

2. CONTROL SURVEYING Fixing the point with respect to horizontal and vertical control. Using surveying instruments. Methods Horizontal control Vertical control 2 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

3. CONTROL SURVEYING Horizontal control 3 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

4. CONTROL SURVEYING Vertical control 4 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

5. CONTROL SURVEYING Horizontal control and its methods employed: Reference mark on known plan position Large structure primary and secondary control points are used Primary control points are used in triangulation Secondary control points are reference to primary control stations. 5 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

6. CONTROL SURVEYING Reference grid: Used for accurate setting out of works of large magnitude Types: Survey grid Site grid Structural grid Secondary grid 6 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

7. CONTROL SURVEYING Survey grid: Drawn on survey plan from the original traverse Original traverse from the control points on the grid Site grid: Used by the designer Design points are related to site grid Site grid should be actually the survey grid 7 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

8. CONTROL SURVEYING Structural grid: Used at when the structural components are large numbers. Used for accuracy It is set out from the site grid points Secondary grid: Used for internal details of the building Other grids are not shown 8 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

9. CONTROL SURVEYING Vertical control and methods: Determine elevation with respect to sea level Used to BM for other survey and high accuracy Also used for boundary survey, route survey, construction and topographic surveys Need at lest two BM and more may be required at depending upon the needs and complexity of the project Also used for construction of water, sewer system, highways, bridges, drains and other infrastructures 9 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

10. CONTROL SURVEYING cont..... Can be done in alone but after often done in conjunction with a horizontal control survey Its used in NOAA ( national oceanic and atmospheric administration) 10 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

11. CONTROL SURVEYING Equipments: Boning rods and travellers (T shape) Sight rails (drilling to ground) Slope rails or batter boards (slope area) Profile boards (board cuts at edges) 11 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

12. CONTROL SURVEYING Triangulation: The system consists of inter connected triangles in which the length of one line called base line Angle of the triangles are measured very precisely Knowing the length of one side and three angles The length of other two sides are computed Disadvantages: Accumulate errors and azimuth 12 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

13. CONTROL SURVEYING Classification of Triangulation system: First order or primary triangulation (total whole country) Second order or secondary triangulation (in between frame work) Third order or tertiary triangulation (within frame work) 13 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

14. CONTROL SURVEYING 14 S.N PARAMETERS 1 st ORDER 2 nd ORDER 3 rd ORDER 1 Average triangle closure Less than 1 second 3 sec 6 sec 2 Maximum triangle closure Not more than 3 seconds 8 sec 12 sec 3 Length of base line 5 to 15 kilometers 1.5 to 5 km 0.5 to 3 km 4 Length of the sides of triangles 30 to 150 kilometers 8 to 65 km 1.5 to 10 km 5 Actual error of base 1 in 300,000 1 in 150,000 1 in 75,0000 6 Probable error of base 1 in 1,000,000 1 in 500,000 1 in 250,000 7 Discrepancy between two measures of a section 10 mm kilometers 20 mm kilometers 25 mm kilometers 8 Probable error or computed distance 1 in 60,000 to 1 in 250,000 1 in 20,000 to 1 in 50,000 1 in 5,000 to 1 in 20,000 9 Probable error in astronomic azimuth 0.5 seconds - 5 sec. CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

15. CONTROL SURVEYING Common figure of system: Single chain triangulations – not accurate Double chain triangulation – used to cover grater area Central point figures – flat countries ( pentagon and hexagon) Quadrilateral – hilly countries (four side) 15 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

16. CONTROL SURVEYING Routine of triangulation survey: Reconnaissance survey Measurement of base line Measurement of horizontal angle Erection of signals and towers computing 16 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

17. CONTROL SURVEYING 1.Reconnaissance survey: Detailed survey Location of the site Characteristics of the contours Selection of triangulation system 17 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

18. CONTROL SURVEYING Factors governing the selection of triangulation station: Easily accessible No obstacles Material available at nearer area Transportation facility Important factors: Determination of distance b/n 2 points or stations Determination of elevation Profile of the intervening (obstacle) ground 18 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

19. WHAT IS THIS ? 19 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

20. CONTROL SURVEYING Signals and Towers: Towers: A tower is a structure erected over a station for the support of the instrument and observing party and is provided when the station or the signal or both are to be elevated. Inner tower - support the instrument only Outer tower- support the observer and signal 20 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

21. CONTROL SURVEYING Towers: Independent to each other-masonry , timber and steel For small height masonry suitable otherwise uneconomical Timber are commonly used-50m height Steel towers are easily erected and dismantled also light weight (BILBY tower 30 to 40m ht-3hours-5men-3tonnes) 21 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

22. CONTROL SURVEYING Signals : A signal is a devices erected to define the exact position of an observed station. Classification : Day light or non luminous (opaque) signal Sun or luminous signal Night signal 22 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

23. CONTROL SURVEYING Requirements of Signals : It should be conspicuous- clear visible against any background Accurate cantered over the station mark It should be suitable for accurate bisection It should be free from phase or exhibit little phase 23 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

24. CONTROL SURVEYING Day light or non luminous (opaque) signal: Consist of various type-Direct sight less then 30km Pole signals used for 6km Signal should be dark colour for visibility against the sky and should painted white. Flag at top the signal Diameter of the signal pole in cm = 1.3D to 1.9D (D in km) Height of signal pole in cm = 13.3D (D in km) 24 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

25. CONTROL SURVEYING Sun or luminous signal: Sun signals are those in which the sun’s rays are reflected to the observing theodolite , either directly as from a beacon or indirectly from a signal target. Used to when the length of sight exceed 30km Instruments used: Heliotrope – consist of plane mirror- Direct reflected rays Heliograph – cantered over the station mark. 25 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

26. CONTROL SURVEYING Night signal: Used in triangulation system at night time. Various forms of oil lamps with reflector or optical collimators for line of sight less than 80km Acetylence lamp designed by captain G.T.Mccaw line of sight up to 80km 26 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

27. CONTROL SURVEYING Phase of signals: Phase signal is the error of bisection which arises from the fact that under lateral illumination the signal is partly in light and partly in shade. Observer sees only the illumination portion and bisects. Two conditions When the observation is made on the bright portion – ref fig A When the observation is made on the bright line – ref fig B 27 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

28. CONTROL SURVEYING Base line measurement: It is most important part of triangulation operations and need to great accuracy Selection of site for base line Fairly level, slope should be uniform and gentle Free from obstruction Base should be inter visible at ground level Firm and smooth, water gaps should be few The site should be extension to primary triangulation 28 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

29. CONTROL SURVEYING Standard of lengths: Marked on meters by metals but small changes in accuracy Great britian – yard of bronze The united states – meter to feet India – old 10 feet bar A = 9.9999566 British feet 29 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

30. CONTROL SURVEYING Base measuring apparatus: Rigid bars (before tape) Contact apparatus (continue end) Optical apparatus (microscope) Compensating base bar (maintain length by 2 metals) Bimetallic non-compensating base bars (using thermometer) Monometallic base bar ( using ice) Flexible apparatus 30 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

31. CONTROL SURVEYING The Colby apparatus: Designed by Maj -Gen Eliminate the effect of change of temperature Linear expansion 3:5 ratio Steel and brass metals are using Brass is coated with a special preparation for steel Compound bar and sprite level are fixed at middle Consist of micro wires (cross wires) 5 frame works (10 ft x 5 + 6 in x 5) = 52ft 6in This work is continued till the end of the base is reached. 31 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

32. CONTROL SURVEYING Flexible apparatus: Long length, time saving, no losses, accuracy, using rough ground also, water gap areas, less expansive, speed of measurements and more check bases . Steel and inverted tape Steel and brass wires Steel tape Thermal expansion nearly 0.00000645/ºF Not accurate at day time, accurate at cloudy and night time 32 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

33. CONTROL SURVEYING Inver tape and wires: Steel alloy containing about 36% nickel The co-efficient of thermal expansion is 0.0000005/ºF Length is changed slowly so never used standard Equipment for base line measurement: Three standardised tapes Straining device, marking tripod or sticks Six thermometers Accurate spring balance 33 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

34. CONTROL SURVEYING The field work: The setting out party Two surveyors and a number of parties The measuring party Two observers, recorder, leveller and staff man (accurate at 0.5 to 1km) Methods: 1.Wheeler’s method by wheeler’s base line apparatus 2.Jaderin’s method 34 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

35. CONTROL SURVEYING Tape corrections: Correction for absolute length Correction for temperature Correction for pull or tension Correction for sag Correction for slope Correction for alignment Reduction to sea level Correction to measurement in vertical plane 35 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

36. CONTROL SURVEYING Correction for absolute length (Ca): Ca = L.c /l Ca- correction for absolute length L-measure length of the line C-correction per tape length L-designed length of the tape Correction for temperature (Ct): Ct = α (Tm-To)L α - co efficient of thermal expansion Tm-mean temperature in the field during measurements To- mean temperature during standardisation of the tape L- measured length 36 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

37. CONTROL SURVEYING Correction for temperature (Ct): Jaderin’s method: Ct (brass) = α b (L s -L b )/ α b - α s Ct (steel) = α s (L s -L b )/ α b – α s Correction for pull or tension (C p or C t ): C p = (P-P o )L/AE P- pull applied during measurements (N) P o- standard pull (N) L-measurement length (m) A-cross section area of the tape (cm 2 ) E-young’s modulus of elasticity (N/cm 2 ) The pull applied in the field should be less than 20 times the weight of the tape. 37 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

38. CONTROL SURVEYING Correction for Sag (C s ): C s = NC s + sag correction for any fractional tape length N-number of whole length tape C s – tape correction per tape length C s = nlw 2 /24p 2 l -total length of the tape W-total weight of the tape n = number of equal span P = pull applied 38 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

39. CONTROL SURVEYING Normal tension( P n ): P n = 0.204w 1 √AE/√ ( P n - P o ) The value of P n is to be determined by trial and error method. Correction for slope or vertical alignment: AB = L = inclined length measured AB 1 = horizontal length h = difference in elevation between the ends. C v = slope correction or correction due to vertical alignment 39 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

40. CONTROL SURVEYING C v = AB- AB 1 = L- √L 2 -h 2 If the grades are uniform length L, we get total slope correction = sum of h 2 /2L If the angle ( θ ) of slope is measured insted of h, the correction is given by C v = L- Lcos θ = l(1-cos θ ) C v =2Lsin 2 θ /2 Correction for horizontal alignment Bad ranging = C h = d2/2L Deformation of the tape in horizontal plane = C h = (d 2 /2L 1 )+(d 2 /2L 1 ) Broken base = C h = (ac β 2 /( a+c )) x 4.2308x10 -8 40 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

41. CONTROL SURVEYING Reduction to mean sea level: Correction (Cmsl) = L-D = Lh /R Correction to measurement in vertical plane: S x = g x /AE ((M+0.5m(2l-x)- p o /g)) 41 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

42. CONTROL SURVEYING Measurement of horizontal angle: Two types of instruments are used in triangulation of high precision 1. Repeating theodolite (Double vertical axis, using 2 or more verniers ) 2. Direction theodolite (1 vertical axis and accuracy) (a) Wild T-3 precision theodolite (b) Wild T-4 universal theodolite 42 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

43. CONTROL SURVEYING Methods of horizontal angle: Method of repetition Reiteration or direct or method of series 43 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

44. CONTROL SURVEYING 44 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

45. CONTROL SURVEYING Methods of horizontal angle: Method of repetition Reiteration or direct or method of series Satellite station : Reduction to centre: In order to secure well conditioned triangle or better visibility objects such as church spires, steel post, flag poles, towers etc.. Sometimes selected as triangulation station, when the observations are to taken from such a station, it is impossible to set up an instrument over it. 45 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

46. CONTROL SURVEYING In such cases a subsidiary station known as satellite station or eccentric station or false station is selected as near to the main station. Observations are taken from same precision as would have been used in the measurement of angle at the true stations. 46 CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N

47. CONTROL SURVEYING 47 Gale’s Table CE6404-Surveying II/Unit 1 by, Shanmugasundaram.N