II/IV B.Tech (Regular/Supply) Degree Examination (Nov-2017) I SEM SURVEYING - I (14CE303) (CIVIL ENGINEERING) Scheme of Evaluation

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1 II/IV B.Tech (Regular/Supply) Degree Examination (Nov-2017) I SEM SURVEYING - I (14CE303) (CIVIL ENGINEERING) Scheme of Evaluation Prepared by Head of the Department Y. Ravi Dr. Ch. Naga Satish Kumar Assistant Professor, Department of Civil Engineering, Bapatla Engineering College. Cell No: & Head of the Department Dr. Ch. Naga Satish Kumar Subject Coordinator Y. Ravi

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4 II/IV B.Tech (Regular/supply) Examination (Nov-2017) First Sem Surveying I (14CE303) Civil Engineering (Scheme of Evaluation) 1. Answer all questions [(12 x 1 = 12M ) Total = 12 M] a. Define the terms accuracy and precision. Accuracy denotes the closeness of a measurement to it s true value Precision of a measurement denotes it s closeness to another measurement of the same quantity. b. What are the duties of a surveyor? i) Field work ii) Office work iii) Care and adjustments of instruments c. The Fore bearing of a line AB is 155 o 25 20". Identify the back bearing of the line AB in quadrant system? Q.B of AB = N 24 o 30 40" W d. Write the errors due to incorrect chain. i) Error due to absolute length ii) Error due to slope e. What is local attraction? Local attraction is the attraction of the magnetic needle to a local magnetic field other than earth s magnetic field f. Define plunging of the telescope. It is the process of rotating the telescope over the horizontal axis through 180 o in the vertical plane. g. State the various rules used to balance traverse. i) Arbitrary method ii) Bowditch rule iii) Transit rule iv) Axis method h. What do you mean by datum surface? Datum or Datum surface is a level surface which is taken as a reference line surface for the determination of elevations of various points. The datum most commonly used is the mean sea level (M.S.L)

5 i. What is the necessity of keeping level midway between back sight and fore sight readings? To balancing the sights. j. Define contour gradient. An imaginary line lying throughout the ground surface and having a constant inclination to the horizontal is called as contour gradient. k. Write any two uses of contour maps. *** For writing any following two give one mark Determination of the character (or Nature) of the terra Selection of a suitable site Determination of sections Intervisibility between two points Location of Determination of catchment area Estimation of reservoir capacity l. Define declination and dip. Declination: The horizontal angle which the magnetic meridian makes with the true meridian is called the magnetic declination. Dip: The vertical angle between longitudinal axis of a freely suspended magnetic needle and the horizontal is called dip. UNIT -I 2. (a) Explain the classification of surveying based on instruments. (7M) For explaining the each one 1M (7x1 =7 M) Classification of surveying based on instruments: Chain surveying is a type of survey in which the surveyor takes measurements in the field and then completes plot calculations and other processes in the office. Chain surveying is best used for smaller planes with few details. Compass surveying is a type of surveying in which the directions of surveying lines are determined with a magnetic compass, and the length of the surveying lines are measured with a tape or chain or laser range finder. The compass is generally used to run a traverse line.

6 Theodolite surveying used for measuring both horizontal and vertical angles, as used in triangulation networks, and geo-location work. It is a tool used in the land surveying and engineering industry, but theodolites have been adapted for other specialized purposes as well. Plane Table Surveying is a graphical method of survey in which the field observations and plotting are done simultaneously. It is simple and cheaper than theodolite survey. It is most suitable for small scale maps. Tachometry (from Greek, quick measure), is a system of rapid surveying, by which the positions, both horizontal and vertical, of points on the earth surface relatively to one another are determined without using a chain or tape or a separate leveling instrument. Photogrammetric Surveying specialize in the science of obtaining reliable spatial information from photographic images. Photogrammetrists analyze aerial and terrestrial photographs to obtain information about physical objects and the environment. EDM survey is a survey done on the principle of optics. A total station or TST (total station theodolite) is an electronic/optical instrument used in modern surveying and building construction. The total station is an electronic theodolite (transit) integrated with an electronic distance meter (EDM) to read slope distances from the instrument to a particular point. 2. (b) The area of the plan of an old survey plotted to a scale of 10 m to 1 cm now measures as cm 2 as found by a planimeter. The plan is found to have shrunk so that a line originally 10 cm long now measures 9.7 cm only. Find (i) The shrunk scale, (ii) True area of the survey(5m) Shinkage factor = shrunk length/actual length = 9.7/10 1 M = 0.97 Shrunk R.F = (1/1000)* 0.97 = 1/ M Shurnk Scale, 1 cm = m True area = Measured area/ (S.F) 2 = 100.2/(0.97) 2 = cm 2 2 M = x (10 m) 2 = m 2

7 (OR) 3. (a) Describe the sources and types of errors in surveying. (6M) For explain sources of errors (3x1 = 3M) For explain types of errors (3x1 = 3M) Sources of errors Instrumental errors Result from any imperfection in the construction or adjustment of instruments and from the movement of individual parts. Personal errors Arise principally from limitations of human senses of sight and touch. Natural errors are caused by variations in wind, temperature, humidity, atmospheric pressure, atmospheric refraction, gravity, magnetic declination, etc. Types of errors Blunders A blunder (or gross error) is a significant, unpredictable mistake caused by human error that often leads to large discrepancies. Blunders are typically the result of carelessness, miscommunication, fatigue, or poor judgment. Systematic Errors Systematic errors are caused by the surveying equipment, observation methods, and certain environmental factors. Under the same measurement conditions, these errors will have the same magnitude and direction (positive or negative). Because systematic errors are repetitive and tend to accumulate in a series of measurements, they are also referred to as cumulative errors. Random (or accidental) errors Are not directly related to the conditions or circumstances of the observation. For a single measurement or a series of measurements, it is the error remaining after all possible systematic errors and blunders have been eliminated. As the name implies, random errors are unpredictable and are often caused by factors beyond the control of the surveyor. Their occurrence, magnitude, and direction (positive or negative) cannot be predicted. Errors of this type are compensating and tend to at least partially cancel themselves mathematically. Because the magnitude is also a matter of chance they will remain, to some degree, in every measurement. 3. (b) Measurements of a line were taken ten times with a steel tape and found as under: , , , , , , , , and m. Determine the standard deviation, standard error of the mean, most probable value, 50% error, maximum error and 99.7%, error. (6M)

8 S. No (1) Measured length (2) Residual (ν) (3) = 2 - Mean value ν 2 (4) X X M Most probable value = Standard deviation (σ) = ν2 n 1 = m 0.5 M = M = m m Standard error of the mean (σ m ) = ν2 n(n 1) = (10 1) 1 M = m m 50 % error = ± σ = ±0.6745* M = ± m m 99.7 % error = ± 3.0σ = ±3* M = ±0.111 m

9 Ranging: UNIT -II 4. (a) Differentiate between ranging and taping. Describe how you would range a survey line between two points which are not intervsible. (6M) When a survey line is longer than a chain length, it is necessary to align intermediate points on chain line so that the measurements are along the line. The process of locating intermediate points on survey line is known as ranging. Taping: Chaining or Taping carries same meaning, The process of taking tape or chain for taking a linear measurement is called taping. Indirect ranging: When the end points are not intervisible, indirect ranging is required. Such a condition occurs where there is high intervening ground between the end points. Indirect ranging is also required when the distance b/w the end points is very long and the ends are not intervisible Procedure: Let A and B be the two end stations of a line with a rising ground between them and M and N the two intermediate points to be established on the chain line (As Shown in Fig). Two surveyors station themselves at M 1 and N 1 such that the person at M 1 can see both ranging rods at N 1 and B, and the person at N 1 can see both ranging rods at M 1 and A. Now the person at N 1 directs the person at M 1 to move to M 2 so as to be in the line with A. Then the person at M 2 directs the person at N 1 to move to N 2 so as to be in the line with B. By successively directing each other, the two persons proceed to the line AB and finally come M at N exactly in the line AB. M and N are the required intermediate points between A and B. 2 M

10 4. (b) Briefly discuss the methods of overcoming difficulties of obstacles in chaining. (6M) While chaining a survey line, sometimes various obstacles are encountered in the filed. The obstacles are of various types Chaining round the obstacle possible Ex: A building, Small pond, a small bend in the river etc. Chaining round the obstacle not possible Ex: A long river across the survey line, Canal Chaining round the obstacle possible : (For explaining any two of the following figures with steps) 2 x 1.5 = 3 M CB = DE CB 2 =DB 2 -CD 2 CB 2 =DB 2 -CD 2 CB = DE CB = DE n

11 Chaining round the obstacle not possible : (For explaining any two of the following figures with steps) 2 x 1.5 = 3 M AB = DE AB = (AE x CA)/ (ED AC) AB = GF AB = AD 2 / CD AB = AC

12 (OR) 5. (a) Explain the procedure to correct the traverse which is affected by local attraction. (6M) First method: In this method, the bearings of the lines are calculated on the basis of the bearing of that line which has a difference of in its fore and back bearings. It is. The amount and direction of error due to local attraction at each of the affected station is found. If, however, there is no such line in which the two bearings differ by 180 0, the corrections should be made from the mean value of the bearing of that line in which there is least discrepancy between the back sight and fore sight readings. If the bearings are expressed in quadrantal system, the corrections must be applied in proper direction. In 1 st and 3 rd quadrants, the numerical value of bearings increase in clockwise direction while they increase in anti clockwise direction in 2 nd and 4 th quadrants. Positive corrections are applied clockwise and negative corrections counter clockwise. Second method: This is more a general method and is based on the fact that though the bearings measured at a station may be incorrect due to local attraction, the included angles calculated from the bearings will be correct since the amount of error is the same for all the bearings measured at the station. The included angles between the lines are calculated at all the stations. If the traverse is a close one, the sum of the internal included angles must be right angles. If there is any discrepancy in this, observational and instrumental errors also exist. Such error is distributed equally to all the angles. Proceeding now with the line, the bearings of which differ by 180 0, the bearings of all other lines are calculated. Special case: Special case f local attraction may arise when we find no line which has a difference of in its fore and back bearings. In that case select the line in which the difference in its fore and back bearings is closest to The mean value of the bearing of that line is found by applying half the correction to both the fore and back bearings of that line, thus obtaining the modified fore and back bearings of that line differing exactly by corrected bearings of other lines are found.. Proceeding with the modified bearings of that line, 2.5 M 2.5 M 1 M

13 5. (b) The following bearings were observed while traversing with a compass and tape. Check bearings for local attraction. Correct the bearings by the method of included angles. (6M) Line F.B B.B 0.5 M 1 M

14 Interior angles 1.5 M 0.5 M 2.5 M

15 UNIT -III 6. (a) Explain the permanent adjustments of theodolite. (6M) Permanent adjustments: (For Each one 1.2 M ) ( 5*1.2 =6 M) The permanent adjustments in case of a transit theodolites are :- i) Adjustment of Horizontal Plate Levels. ii) iii) iv) The axis of the plate levels must be perpendicular to the vertical axis. Collimation Adjustment. The line of collimation should coincide with the axis of the telescope and the axis of the objective slide and should be at right angles to the horizontal axis. Horizontal axis adjustment. The horizontal axis must be perpendicular to the vertical axis. Adjustment of Telescope Level or the Altitude Level Plate Levels. The axis of line of collimation. the telescope levels or the altitude level must be parallel to the v) Vertical Circle Index Adjustment. The vertical circle vernier must read zero when the line of collimation is horizontal. 6. (b) State what errors are eliminated by repetition method. how will you set out a horizontal angle by method of repetition? (6M) Advantages: (Errors eliminated by this method) Errors due to eccentricity of verniers and centres are eliminated. Errors due to inaccurate bisection of the signal are eliminated. Other errors are also minimized as the sum is divided by the number of repetitions. 1 M

16 Procedure: Angle AOB is to be measured by repetition process. Vernier A is set to 0 o and vernier B to 180 o The upper clamp is tightly fixed, and the lower one is loosened. By turning the telescope, the ranging rod at A is perfectly bisected with the help of lower clamp screw and lower tangent screw. Here the initial reading of the vernier A is 0 o. The upper clamp is loosened and the telescope is turned clockwise to perfectly bisect the ranging rod at B. The upper clamp is clamped. Suppose the reading on veriner A is 30 o The lower clamp is loosened and the telescope is turned in anticlockwise to bisect the ranging rod at A. here the initial reading is 30 o for the second observation The lower clamp is tightened. The upper one is loosened and the telescope is turned clockwise to exactly bisect the ranging rod at B. let the reading on vernier A be 60 o 5 M The initial reading for third observation is set to 60 o. Angle AOB is again measured. Let the final angle be 90 o which is the accumulated angle. Angle AOB is 30 o The face of the instrument is changed and the previous procedure is followed. The mean of the two observation gives actual angle AOB

17 (OR) 7. a) What is gales traverse table? Describe the steps necessary for complete traverse computations. (6M) Gales traverse table: Traverse computations are usually done in a tabular form, known as gales traverse table 1 M Steps in gales traverse table: Column 1: Enter the names of the stations at which the instrument is set up, say P, Q, R, etc Column 2: Enter the names of traverse sides in between an instrument station and its forward station such as PQ, QR, RS etc. 1M Column 3: Enter the observed length of the traverse sides. Column 4: Enter the angles observed at the stations. These may be included / interior angles or deflection angles. Sum of all the angles are entered in the end of this column. Check if there is any error of closure of the observed angles (The type of checking depends on the on the type of angles observed and the type of traverse). Column 5: If there is any error of closure, necessary corrections are to computed and the same is to be presented in this column. Thus, column 5 provides the correction for error of closure. 1M Column 6: After making necessary correction to the observed angles, adjusted angles are computed and thus adjusted angles are represented in column 6. Column 7 : From the known azimuth (from previous surveying or determined before the starting of traversing) of a line present in the site and/ or from known angle between the line of known azimuth and that of a traverse side, compute the WCB of the all the traverse sides using the adjusted angles of column 6. The WCB of traverse sides are represented in column 7. Column 8: Compute the consecutive coordinates of the stations in terms of departure and latitude with appropriate algebraic sign from the observed length (Column 3) and the WCB (Column 7) of the sides. The same are represented in column 8 along proper row and under proper sub-heading. Check the error of closure of the traverse. If any error is present, adjustment and balancing of traverse is to be done. The algebraic sum of the departures and latitudes are to be represented at the end of the appropriate columns. 2M

18 Column 9: The error associated with the traverse is to be distributed to all the stations in such a way that there is no error of closure. Thus, corrections are to be computed for different stations. Usually Bowditch's Analytical method is usually adopted to find the correction for each individual consecutive coordinates and the same is represented in column 9 under appropriate sub-heading. At the end of the column, sum of the corrections are also represented. It is to be checked that the total correction should be same as the amount of error but opposite in nature Column 10: The adjusted consecutive coordinates of the stations are computed making due corrections (column 9) to the consecutive coordinates (column 8). The adjusted consecutive coordinates of the stations are thus represented in column 10. 2M Column 11: From the known coordinates of at least one of the stations the Independent coordinates of all the other stations are computed and the same is represented in column b) A closed traverse were conducted round an obstacle and the following observations were made. Work out the missing quantities. Line Length (m) Azimuth AB o 30 (6M) BC o 20 CD o 30 DE? 230 o 0 EA? 150 o 10 Let l DE and l EA are the lengths of the lines DE and EA L = Cos 98 o Cos 30 o Cos 298 o 30 + l DE Cos 230 o 0 + l EA Cos 150 o 10 = 0 (1.5 M) l DE l EA = (1) (1 M) 500 Sin 98 o sin 30 o Sin 298 o 30 + l DE Sin 230 o 0 + l EA Sin 150 o 10 = 0 (1.5 M) l DE l EA = (2) (1 M) By solving equations (1) and (2) we get l DE = m (0.5 M) l EA = m (0.5 M)

19 UNIT-IV 8. a) A level set up on extended line BA in a position 70 m from A and 100 m from B reads m on a staff held at A and m on a staff held at B, the bubble having been carefully brought to the centre of its run before each reading. The R.L s of the tops of pegs A and B are m and m respectively. Find i) the collimation error and ii) the readings that would have been obtained had there been no collimation error. (6M) 2 M 1 M 2 M 1 M

20 8. b) What are different errors in leveling? How would you minimize errors? (6M) For writing any three in each case 2 M (3 x 2 = 6M) *** If they are written only headings in each case give 3 Marks 1. INSTRUMENTAL ERRORS Error in permanent adjustment of level: For any major surveying work, instrument needs to be tested and if required, gets to be adjusted. For small works, bubble of the level tube should be brought to the center before each reading and balancing of sights is to be maintained. Staff defective and/or of non-standard quality: The graduation in staff may lack standard distance and thus may cause error in reading. In an ordinary leveling, the error may be negligible but in the case of precise leveling, the graduations are to be standardized with invar tape. Error due to defective level tube: The bubble of the level tube may remain central even though the bubble axis is not horizontal due to its sluggishness or it may take considerable time to occupy central position, if it is very sensitive. Also, there may be irregularity in the curvature of the tube causing delirious effect. Error due to defective tripod: The tripod stand should be strong and stable otherwise it causes setting of the instrument unstable and considerable time is required to make it level. The nuts provided at the joints of the legs to the tripod head should be well-tightened before mounting the instrument. The tripod should be set up on a stable, firm ground. 2. PERSONAL ERRORS Due to imperfection in temporary adjustment of the instrument: These errors are caused due to careless setting up of the level, improper leveling of the instrument, lack in focus of eyepiece or/and objective and error in sighting of the staff. Careless set-up of the instrument: If the instrument is not set up firmly, it gets disturbed easily. If the ground is not firm, it may settled down and on hard ground, it may get slipped. Imperfect leveling of the instrument: Due to improper leveling of the instrument, bubble does not remain at the center when the sights are taken resulting error in reading. To avoid the error, the bubble should be brought to the Centre before each reading. Imperfect focusing: If either the eye-piece or the objective or both are not properly focused, parallax and thus error in the staff readings occur. Due to movement of eyes if there is any apparent change in the staff reading the eye-piece and objective need proper focusing.

21 Errors in sighting: This occurs when the horizontal cross-hair does not exactly coincide with the staff graduation or it is difficult to see the exact coincidence of the cross hairs and the staff graduations. The error can be minimized by keeping the sight distance small. Error due to staff held Non-vertical: If the staff is not held vertical, the staff reading obtained is greater than the correct reading. To reduce the error, the staff should be held exactly vertical or the staff man should be asked to waive the staff towards the instrument and then away from the instrument and the lowest reading should be taken. Errors in reading the staff: These errors occur if staff is read upward, instead of downwards, read against the top or bottom hair instead of the central hair, mistakes in reading the decimal part and reading the whole meter wrongly. Errors in recording: The common errors are entering a wrong reading (with digits interchanged or mistaking the numerical value of a reading called by the level man), recording in wrong column, e.g., B.S. as I.S., omitting an entry, entering the inverted staff reading without a minus sign etc. Errors in computing: adding the fore sight reading instead of subtracting it and or subtracting a back sight reading instead of adding. 3. ERRORS DUE TO NATURAL CAUSES Error due to curvature: In case of small sight distance error due to the curvature are negligible, but if the sight distances are large, the error should be estimated and accounted for, as discussed below. However, the error can be minimized through balancing of sight or reciprocal observation. Error due to refraction: It varies with temperature, terrain and other atmospheric conditions. It is usually considered to be one seventh times but in opposite nature to the error due to curvature. To minimize this error, reciprocal observation at the same instant of time is required to be adopted. Errors due to wind: Strong wind disturbs leveling of an instrument and verticality of staff. Thus, it is advisable to suspend the work in this condition. Errors due to sun: Due to bright sunshine on the objective, staff reading cannot be taken properly. To avoid such error, it is recommended to maintain a shed to the objective. Errors due to temperature: Temperature of the atmosphere disturbs setting of parts of instrument as well as causes fluctuation in the refraction of the intervening medium. These lead to error in staff reading. Disturbance caused to instrument may be minimized by placing the instrument under shed

22 (OR) 9. a) What are the methods of locating contours and explain briefly. (6M) Generally there are two methods for locating contours 1. Direct methods 2. Indirect methods. 1. Direct Methods It consists in finding vertical and horizontal controls of the points which lie on the selected contour line. For vertical control levelling instrument is commonly used. A level is set on a commanding position in the area after taking fly levels from the nearby bench mark. The plane of collimation/height of instrument is found and the required staff reading for a contour line is calculated. The instrument man asks staff man to move up and down in the area till the required staff reading is found. A surveyor establishes the horizontal control of that point using his instruments. After that instrument man directs the staff man to another point where the same staff reading can be found. It is followed by establishing horizontal control. Thus several points are established on a contour line on one or two contour lines and suitably noted down. Plane table survey is ideally suited for this work. After required points are established from the instrument setting, the instrument is shifted to another point to cover more area. The level and survey instrument need not be shifted at the same time. It is better if both are nearby so as to communicate easily. For getting speed in levelling some times hand level and Abney levels are also used. This method is slow, tedious but accurate. It is suitable for small areas. 2 M 2. Indirect Methods In this method, levels are taken at some selected points and their levels are reduced. Thus in this method horizontal control is established first and then the levels of those points found. After locating the points on the plan, reduced levels are marked and contour lines are interpolated between the selected points.

23 For selecting points anyone of the following methods may be used: (a) Method of squares, (b) Method of cross-section, or (c) Radial line method. Method of Squares: In this method area is divided into a number of squares and all grid points are marked (Ref. following Fig.) Commonly used size of square varies from 5 m 5 m to 20 m 20 m. Levels of all grid points are established by levelling. Then grid square is plotted on the drawing sheet. Reduced levels of grid points marked and contour lines are drawn by interpolation 2 M Method of Cross-section: In this method cross-sectional points are taken at regular interval. By levelling the reduced level of all those points are established. The points are marked on the drawing sheets, their reduced levels (RL) are marked and contour lines interpolated. Following Figure shows a typical planning of this work. The spacing of crosssection depends upon the nature of the ground, scale of the map and the contour interval required. It varies from 20 m to 100 m. Closer intervals are required if ground level varies abruptly. The cross- sectional line need not be

24 always be at right angles to the main line. This method is ideally suited for road and railway projects. 1 M Radial Line Method: [Following Fig.]. In this method several radial lines are taken from a point in the area. The direction of each line is noted. On these lines at selected distances points are marked and levels determined. This method is ideally suited for hilly areas. In this survey theodolite with tacheometry facility is commonly used. 1 M

25 9. b) What do you understand by contour gradient? Explain its importance in route alignment for a road in hilly area. (6M) Contour gradient An imaginary line lying throughout the ground surface and having a constant inclination to the horizontal is called as contour gradient. 1 M Location of route 1 M To locate a rising gradient of 1 in 100 from the station P, a level is set up at a commanding position and back sight is taken at P. Let the back sight reading be m. The staff reading at any point X on the contour gradient can be calculated from its distance from P. For the distance XP of 20 m, the required staff reading would be 4 M (20/100) = m To locate the pint X on the ground, staff man holds the 20 m -mark of the tape, keeping the zero-mark at P, and moves till the staff reading of m is obtained. Like wise, the staff readings for other points at known distance from P, are calculated, and the points are located. ********** THE END***********

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