linear measurement introduction(part1) Arc.pptx

introduction to surveying and linear measurement

1. Distance measurement Definitions Surveying may be simply defined as the art of making measurements. Surveying involves the measurements of Distances, angles and elevations. It also involves staking out the lines and grades needed for the construction of buildings, roads, dams, and other engineering structures . In addition to the field measurements, surveying includes the computation of areas , volumes , and the preparation of necessary maps and diagrams. 10/14/2024 1 prepared by Mulugeta Y.

2. Cont… More precisely, Surveying can be defined as the art and Science of determining the relative positions of various points on, above or below the surface of the earth . When we say the relative positions of points it means that determining the relative positions of points in reference to another point or reference point/station. For example, Adama City is found at about 100 kilometers East of Addis Ababa . In this example, it is obvious that the (relative position) location of Adama city is described in reference to Addis Ababa and that of Adama University is in reference to Adama City.   10/14/2024 2 prepared by Mulugeta Y.

3. Importance of Surveying Surveying plays an essential role in the planning, design, layout and construction of our physical environment and infrastructure. Roads, Bridges, Buildings, water supply sewerage, drainage systems and many other essential public works, projects could never be built without surveying technology. in construction and land-use projects 10/14/2024 3 prepared by Mulugeta Y.

4. Cont… surveying process starts with the reconnaissance survey establish the best sites for survey stations Collect the necessary data produce plans used for planning Engineering projects, marking boundary corners or lines, computations of areas & volumes After finalizing the design or detail drawing, setting out will be done. 10/14/2024 4 prepared by Mulugeta Y.

5. Types of surveying / Primary Division of Surveying Surveying is thus primarily divided in two types: Plane surveying Geodetic Surveying 10/14/2024 5 prepared by Mulugeta Y.

6. Classification of Surveying based on purpose/ Applications/method Control Surveying Cadastral Surveying Topographic Surveying Construction Surveying Route survey . Photorgrametric Surveying Hydrographic surveys Cartographic surveying City surveys Mine Surveys, Geological surveys, satellite surveys, Astronomic 10/14/2024 6 prepared by Mulugeta Y.

7. 10/14/2024 7 prepared by Mulugeta Y.

8. Classification of Survey based on Instruments used Chain Surveying : is the simplest type of surveying in which only linear measurements are taken with a chain or tape Compass surveying : In this type of surveying, the horizontal angles are measured with the help of a magnetic compass, in addition to the line or measurements with a chain or a tape. Leveling : this is a type of survey in which a leveling Instrument is used for determination of relative elevations (levels) of various points on, above or below the surface of the earth 10/14/2024 8 prepared by Mulugeta Y.

9. Units of measurements Basic metric units of Length:- the is unit of measurement for length is the meter and is subdivided into millimeter (mm), centimeter (cm), decimeter (dm) meter (m)& kilometer. 1cm = 10mm 1m = 10dm 1dm = 10cm 1km = 1000m Basic metric units of Area:- when the unit of length is multiplied by the unit of length, the result is the unit of area which is expressed by m 2 . 1cm 2 = 100mm 2 1m 2 = 100dm 2 1dm 2 = 100cm 2 1km 2 = 10 6 m 2 Basic metric units of Volume :- when a unit of length (m) is multiplied by the unit of area, we get the unit of volume which is given by m 3 . 1cm 3 = 10mm 3 1m 3 = 10dm 3 1dm 3 = 10 mm 3 1km 3 = 10 6 m 3 10/14/2024 9 prepared by Mulugeta Y.

10. Plane Angular Measure Radian system: 1 full circle = 2π rad. Sexagesimal System: 1 full Circle = 360 ,1 = 60’, 1’ = 60’’ Centisimal System: 1 full Circle = 400 , 1 g = 100 g , 1 g = 10 mg The relationship b/n these systems is given as follows: 1 full circle = 2 π rad = 360 = 400 10/14/2024 10 prepared by Mulugeta Y.

11. Conversion Example: 1. convert 37 57’15’’ in to grad and rad Solution A. 360 = 400 37 57’15’’ x 400 = 42.171 g 37 57’15’’ = ? 360 B. 360 = 2πrd 37 57’15’’ x 2πrad = 0.662rad . 37 57’15’’ = ? 360 2.Convert 50 g in to degree and rad A. 360 = 400 g 50 g x360 = 45 ? = 50 g 400 g B. 400 g = 2πrad 50 g x 2πrad = 0.785rad 50 g = ? 400 g 10/14/2024 11 prepared by Mulugeta Y.

12. Basic Measurements in Surveying Horizontal distance Vertical Distance Horizontal Angles and Vertical Angles. 10/14/2024 12 prepared by Mulugeta Y.

13. Horizontal Distance distance between two points as the distance measured between the points which are in a horizontal plane, the plane which is perpendicular to the vertical direction at a point or direction of gravity at the points or the horizontal projection of the slope distance between points which are on a slopping Ground. 10/14/2024 13 prepared by Mulugeta Y.

14. Con… Horizontal distance is the distance measured between points which are in a horizontal plane or the horizontal projection of the slope distance between points on a sloping ground. The most common methods for measuring horizontal distances include: pacing, stadia, taping, and electronic distance measurement (EDM). 10/14/2024 14 prepared by Mulugeta Y.

15. Tape Measurement Types of Tapes The most common surveying tapes are made of a steel ribbon of constant cross-section bearing graduations at regular intervals. Others are made of a steel alloy or of a metallic or non metallic cloth . There is great diversity of tapes with respect to lengths and widths and manner of graduation 10/14/2024 15 prepared by Mulugeta Y.

16. Con… steel alloy tapes, known as Invar or Lovar , have a coefficient of thermal expansion about one thirtieth that of steel and are used when the taping specification prescribe a high order of accuracy. 10/14/2024 16 prepared by Mulugeta Y.

17. Instruments & Taping Accessories 1 . TAPE:- a tape is an instrument, mostly graduated in meter, decimeter and centimeter, used for measuring accurate lengths. Measuring tapes can be classified depending up on the material in their man facture. Eg . Linen tape, steel tape, invar tape, synthetic tape… 2. ARROWS (Chain pins) :- they are used to mark the position of the ends of the tape on the ground. 3. PEGS :- Wooden pegs are used to mark the position of the survey station or the end points of the survey line. 4. RANGING RODS : - the process of locating a number of points on a long survey is called ranging. Ranging rods are used to locate intermediate points such that these points lie on the straight line joining the end stations. 10/14/2024 17 prepared by Mulugeta Y.

18. Cont… 5. PLUMB BOBS :- They are made up of metal used for fixing range poles vertically, centering surveying instruments, and transferring pts from tape to ground station while measuring distance over sloping ground. 6. OPTICAL SQUARE : - it is a useful instrument often used in combination with tape surveys for producing rectangular angles (100gon or 90 ). 10/14/2024 18 prepared by Mulugeta Y.

19. Taping Accessories 10/14/2024 19 prepared by Mulugeta Y.

20. C0nt… Pegs Arrow Ranging rod or poles Tripod Plumb bob Optical Square 10/14/2024 20 prepared by Mulugeta Y.

21. Horizontal Distance over Level Ground / Taping on level ground/ 1. Lining In. The line to be measured should be marked at both ends and   2. Applying Tension . The rear end of a tape is held over the first point, while the forward end is lined in.   3. Plumbing . Weeds, brush, obstacles and surface irregularities may make it undesirable to lay a tape on the ground. Instead, the tape is held above ground in a horizontal position. 4. Marking Tape Lengths. When the tape has been lined in properly, tension has been applied and the rear field assistant is over the point, 'mark' is called out.   5. Reading the Tape and Recording the Distance. Accurate field work may be cancelled by careless recording.   10/14/2024 21 prepared by Mulugeta Y.

22. The simplest taping operation is measuring over level ground where the tape can be stretched out while fully supported by the ground, as shown in figure 10/14/2024 22 prepared by Mulugeta Y.

23. b. Taping Horizontal Distance over sloping Ground Consider two point A and B which are several tape lengths apart along a slope. The horizontal distance between the two points can be measured by supporting the tape at the two ends only, as shown in figure below, using the method called tapping break . 10/14/2024 23 prepared by Mulugeta Y.

24. Taping Slope Distance Where d is the horizontal distance, s is the slope distance, and is h the difference in height between the two end points . . S h d 10/14/2024 24 prepared by Mulugeta Y.

25. C0nt… Note that the accuracy of the computed horizontal distance d depends on the accuracy of measured slope distances & on the accuracy of the height difference h. 10/14/2024 25 prepared by Mulugeta Y.

26. Horizontal measurement on uneven ground 10/14/2024 26 prepared by Mulugeta Y.

27. Errors in Linear measurements and their corrections Errors of measurements are of three kinds: 1. MISTKES - mistakes are errors that arise from inattention, inexperience, carelessness and poor judgment or confusion in the mind of the observer. 2. SYSTEMATIC ERRORS - they always follow some definite mathematical or physical law, and a correction can be determined and applied. Eg . The error in the length of the steel tape due to change in temperature is a systematic error. RANDOM (ACCIDENTAL) ERRORS:- are those which remain after mistakes and systematic errors have been eliminated and are caused by a combination of errors. represent the limit of precision in the determination of a value, i.e., due to lack of perfection in the human eye. E.g. In measuring a distance with a scale tape marked in centimeters, one has to estimate a distance of 5mm as 6mm or 4mm because the eye cannot judge the exact division . 10/14/2024 27 prepared by Mulugeta Y.

28. COMMON ERRORS IN TAPING AND THEIR CORRECTION 1 1. Incorrect length of tape. 2. Temperature other than standard. 3. Inconsistent pull. 4. Sag. 5. Poor alignment. 6. Tape not horizontal. 7. Improper plumbing. 8. Faulty marking. 9. Incorrect reading or interpolation. 10/14/2024 28 prepared by Mulugeta Y.

29. Tape correction formulas 10/14/2024 29 prepared by Mulugeta Y.

30. Optical Methods In the case of horizontal line of sight, the horizontal distance between the instrument at A and the staff at B is computed by D= KS,where , K=100, S=staff intercept. 10/14/2024 30 prepared by Mulugeta Y.

31. Electronic Distance Measurement Electronic distance measurement (EDM), introduced in the 1950s The EDM equipments which are commonly used are mainly electronic or microwave systems and electro-optical instruments. EDM instruments are manufactured for use with theodolites and as integral or modular components of total station instruments. 10/14/2024 31 prepared by Mulugeta Y.

32. Cont… Current EDM instruments use infrared light or laser light. Microwave systems (now largely outdated) use a receiver/transmitter at both ends of the measured line, whereas infrared and laser systems utilize a transmitter at one end of the measured line and a reflecting prism at the other end. 10/14/2024 32 prepared by Mulugeta Y.