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Basic Surveying

Basic Surveying. CE 263. Introduction to Surveying. Definition : Surveying is the science and art of determining the relative positions of points above, on, or beneath the earth’s surface and locating the points in the field. The work of the surveyor consists of 5 phases:.

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Basic Surveying

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  1. Basic Surveying CE 263

  2. Introduction to Surveying • Definition: Surveying is the science and art of determining the relative positions of points above, on, or beneath the earth’s surface and locating the points in the field.

  3. The work of the surveyor consists of 5 phases: • Decision Making – selecting method, equipment and final point locations. • Fieldwork & Data Collection – making measurements and recording data in the field. • Computing & Data Processing – preparing calculations based upon the recorded data to determine locationsin a useable form. • Mapping or Data Representation – plotting data to produce a map, plat, or chart in the proper form. • Stakeout – locating and establishing monuments or stakes in the proper locations in the field.

  4. 2 Categories of Surveying: • Plane Surveying – surveying with the reference base for fieldwork and computations are assumed to be a flat horizontal surface. • Generally within a 12 mile radius the pull of gravity is very nearly parallel to that at any other point within the radius and thus horizontal lines can be considered straight. • Geodetic Surveying – surveying technique to determine relative positions of widely spaced points, lengths, and directions which require the consideration of the size and shape of the earth. (Takes the earth’s curvature into account.)

  5. 7 Types of Surveys: • Photogrammetry– mapping utilizing data obtained by camera or other sensors carried in airplanes or satellites. • Boundary Surveying – establishing property corners, boundaries, and areas of land parcels. • Control Surveying – establish a network of horizontal and vertical monuments that serve as a reference framework for other survey projects. • Engineering Surveying – providing points and elevations for the building Civil Engineering projects.

  6. 7 Types of Surveys: • Topographic Surveying – collecting data and preparing maps showing the locations of natural man-made features and elevations of points o the ground for multiple uses. • Route Surveys – topographic and other surveys for long – narrow projects associated with Civil Engineering projects. • Highways, railroads, pipelines, and transmission lines. • Hydrographic Surveying – mapping of shorelines and the bottom of bodies of water. • Also known as bathymetric surveying.

  7. Brief History of Surveying: • Surveying had it’s beginning in Egypt about 1400 BC • Land along the Nile River was divided for taxation. Divisions were washed away by annual floods. • “ROPE-STRETCHERS” Egyptian surveyors were created to relocate the land divisions (measurements were made with ropes having knots at unit distances). • Extensive use of surveying in building of Egyptian monuments • Greeks: expanded Egyptian work and developed Geometry. • Developed one of the earliest surveying instruments – Diopter (a form of level).

  8. Brief History of Surveying: • Romans: developed surveying into a science to create the Roman roads, aqueducts, and land division systems. • Surveyors held great power, had schools and a professional organization • Developed several instruments: • Groma – cross instrument used to determine lines and right angles • Libella – “A” frame with a plumb bob used for leveling • Chorobates – 20’ straight edge with oil in notch for leveling • Middle Ages: land division of Romans continued in Europe. • Quadrans – square brass frame capable of turning angles up to 90° and has a graduated scale developed by an Italian named Von Piso.

  9. Brief History of Surveying: • 18th & 19th Century in the New World: the need for mapping and marking land claims caused extensive surveying, especially by the English. • 1785: United Stated began extensive surveys of public lands into one mile square sections • 30 states surveyed under the U.S. Public Land System (also called the Rectangular System) • 1807: United States Geological Survey founded to establish an accurate control network and mapping • Famous American Surveyors: George Washington, Thomas Jefferson, George Rogers Clark, Abe Lincoln and many more.

  10. Brief History of Surveying: • 20th Century and Beyond: As technology advanced, population increased, and land value caused development of licensure for surveyors in all states. • Educational requirements for licensure began in the early 1990’s • Capable of electronic distance measurement, positioning using global positioning systems, construction machine control, and lidar (scanning) mapping • Involvement in rebuilding of the infrastructure and geographic information systems (GIS) • Shortage of licensed professionals is projected well into the 21st century

  11. Measurement of Distance • Linear measurement is the basis of all surveying and even though angles may be read precisely, the length of at least one line in a tract must be measured to supplement the angles in locating points. Methods of measuring a horizontal distance: • Rough Measuring: Pacing, Odometer readings, Tacheometry(stadia), Taping, EDM, and GPS • Only the last three meet survey accuracy requirements • Distance from stadia: (High wire-Low wire) * 100 = Distance (ft) • More accurate measuring: taping, EDM (1966), GPS • EDM and GPS are most common in today’s surveys • In pacing, one establishes the # of paces/100’ by counting the # of paces over a pre-measured 300’ line

  12. Measurement of Distance • Taping: applying the known length of a graduated tape directly to a line a number of times. 2 Problems exist in Taping: • Measuring the distance between two existing points • Laying out a known distance with only the starting point in place

  13. Measurement of Distance 6 Steps of Taping • Lining in – shortest distance between two points is a straight line. • Applying tension – rear chain is anchor and head chain applies required tension. • Plumbing – horizontal distance requires tape to be horizontal. • Marking tape lengths – each application of the tape requires marking using chaining pins to obtain total length. • Reading the tape – the graduated tape must be read correctly. • Recording the distance – the total length must be reported and recorded correctly.

  14. Types of Chains and Tapes • Before the ability to make steel rods and bands, sticks were cut into lengths of 16.5’ (Rod) and they were laid end to end to measure. • Gunter’s Chain • 66’ long with 100 link w/each link being 7.92 inches or 66 feet long • Developed by Edmund Gunter in 1600’s in England and made with individual wires with a loop at each end connected • Chain had between 600-800 wearing surfaces which with hard use would wear and cause chain to elongate • Measurements were recorded in chains and links • 7ch 94.5lk = 7.945 ch = 7.945 X 66’/ch = 524.37’ • 1 chain = 4 rods; 80 chains = 1 mile

  15. Types of Chains and Tapes • Engineer’s Chain • Same construction as Gunter’s Chain, but each link is 1.0’ long and was used for engineering projects • Surveyor’s and Engineer’s Tapes • Made of ¼” to 3/8” wide steel tapes in 100’; 200’; 300’ lengths • Multiple types of marking and graduation: • Available in chains, feet, and metric • Graduated: • Throughout – feet and tenths marked the entire length • Extra foot – feet marked the length of the tape with additional foot at the 0 end graduated in tenths and hundreds of the foot

  16. Types of Chains and Tapes • Invar Tapes • Made of special nickel steel to reduce length variations due to temperature changes • The tapes are extremely brittle and expensive • Used most of the time for standard comparison of tapes • Cloth, Fiberglass, and PVC Tapes: • Lower accuracy and stored on reels. Used for measurement of 0.1’ accuracy requirements Accessories • Chaining Pins – set of 11, used to mark the tape lengths • Hand Level – used to determine required plumbing height • Plumb Bob – used to transfer the mark from the tape to ground • Tension Handle – used to maintain correct tension on tape

  17. Taping (Field Process) • The line to be taped should be marked at both ends • Keeps measurement on line • Rear chain person should keep the head chain person on line • 1’ of line error/100’ = 0.01’ error in length • Applying Tension • Rear chainman is anchor and should hold 100’ mark over point • Tension is applied by head chain person – normally 12 to 30 pounds of pull • Tapes are standardized at 12 lbs., but greater is utilized to compensate for sag

  18. Taping (Field Process) • Plumbing • One end of tape is raised to maintain a horizontal measuring plane. ONLY one end is elevated • This allows measurements to be made on uneven ground • If a high spot exists in center, “break” tape by measuring to the top and then move forward to complete the distance

  19. Slope Measurements: • Generally, measurements are made horizontally, but on even, often man-made slopes the distance can be measured directly on the slope, but the vertical or zenith angle must be obtained. • Horizontal Distance = sin Zenith Angle X Slope Distance • Horizontal Distance = cos Vertical Angle X Slope Distance

  20. Stationing: • Starting point is 0+00 and each 100’ is one station 700’ from starting point is Station 7+00 • If distance is 857.23’ from starting point, it is expressed as Station 8+57.23

  21. Taping Error: • Instrumental Error – a tape may have different length due to defect in manufacture or repair or as the result of kinks • Natural Error – length of tape varies from normal due to temperature, wind and weight of tape (sag) • Personal Error – tape person may be careless in setting pins, reading the tape, or manipulating the equipment • Instrumental and natural error can be corrected mathematically, but personal error can only be corrected by remeasure. • When a tape is obtained, it should either be standardized or checked against a standard. • Tapes standardized at National Bureau of Standards in Maryland • Standardized at 68 degrees F and 12 lbs. tension fully supported.

  22. Tape Error Correction: • Measuring between two existing points: • If a tape is long, the distance will be short, thus any correction must be added • If tape is short, the distance will be long, thus any correction must be subtracted • If you are setting or establishing a point, the above rule is reversed. Generally can correct for tape length, temperature, tension, and sag, but tension and sag are negated by increasing tension to approximately 25 – 30 lbs.

  23. Error in Taping: • Tape Length: Correction per foot = Error in 100’/100’ • If tape was assumed to be 100.00’ but when standardized was found to be 100.02’ after distance measured at 565.75’ • then: Correction =(100.02-100.00)/100.00 = 0.0002’ error/ft • 565.75’ X .0002’/’ = 0.11’ correction and based upon rule, must be added, thus true distance = 565.86’ • If tape had been 99.98’ then correction would be subtracted and true distance would be 565.64’

  24. Error in Taping: • Temperature – Tapes in U.S. are standardized at 68F; the temperature difference above or below that will change the length of the tape • Tapes have a relatively constant coefficient of expansion of 0.0000065 per unit length per F • CT = 0.0000065(Temp (F)-68) Length • Example: Assume a distance was measured when temperature was 30°F using a 100’ tape was 872.54’ (68 – 30) X 0.00000645 X 872.54’ = 0.21’ error tape is short, thus distance is long, error must be subtracted and thus 872.54’ – 0.21’ = 872.33’ (note: temperature difference is absolute difference)

  25. Surveying Metric Conversion • 1 Survey Foot = 1200 / 3937 meters • 1 Meter = 3937 / 1200 Survey Feet

  26. Transit • Transit is the most universal of surveying instruments – primary use is for measurement or layout of horizontal and vertical angles – also used to determine vertical and horizontal distance by stadia, prolonging straight lines, and low-order leveling. 3 Components of the Transit • Alidade – Upper part • Horizontal limb – Middle part • Leveling-head assembly – Lower part

  27. Transit • Alidade (upper part) • Circular cover plate w/2 level vials and is connected to a solid conical shaft called the inner spindle. • Contains the vernier for the horizontal circle • Also contains frames that support the telescope called STANDARDS • Contains the vertical circle and its verniers, the compass box, the telescope and its level vial

  28. Transit • Horizontal Limb (middle part) • This is rigidly connected to a hollow conical shaft called the outer spindle (which holds the inner spindle) • Also has the upper clamp, which allows the alidade to be clamped tight • Also contains the horizontal circle

  29. Transit • Leveling-Head Assembly (lower part) • 4 – leveling screws • Bottom plate that screws into tripod • Shifting device that allows transit to move ¼ to 3/8” • ½ ball that allows transit to tilt when being leveled • The SPIDER – 4-arm piece which holds the outer spindle • Lower clamp – allows rotation of outer spindle

  30. Telescope: Similar to that of dumpy level, but shorter Parts – objective, internal focusing lens, focusing wheel, X-hairs, & eyepiece Scales: horizontal plate or circle is usually graduated into 30’ or 20’ spaces with graduations from 0 to 360 in both directions Circles are graduated automatically by machine and then scanned to ensure accuracy They are correct to with in 2” of arc

  31. Verniers • Least count = Lowest # of reading possible – determines accuracy • Least Count = (Value of smallest division on scale)/(# of divisions on vernier)

  32. Verniers • 3 Types of Verniers • Direct or single vernier – reads only in one direction & must be set with graduations ahead of zero • Double vernier – can be read clockwise or counterclockwise–only ½ is used at a time • Folded vernier – avoids a ling vernier plate • ½ of the graduations are placed on each side of the index mark • Use is not justified because it is likely to cause errors

  33. Verniers • The vernier is always read in the same direction from zero as the numbering of the circle, i.e. the direction of the increasing angles • Typical mistakes in reading verniers result from • Not using magnifying glass • Reading in the wrong direction from zero, or on the wrong side of a double vernier • Failing to determine the least count correctly • Omitting 10’, 15’, 20’, 30’ when the index is beyond those marks

  34. Properties of the Transit • Designed to have proper balance between: • Magnification and resolution of the telescope • Least count of the vernier and sensitivity of the plate and telescope bubbles • Average length of sight of 300’ assumed in design • Specifications of typical 1’ gun: • Magnification – 18 to 28X • Field of view - 1 to 130’ • Minimum focus – 5’ to 7’ • X-hairs usually are + with stadia lines above and below • The transit is a repeating instrument because angles are measured by repetition and the total is added on the plate • Advantages of this: • Better accuracy obtained through averaging • Disclosure of errors by comparing values of the single and multiple readings

  35. Handling the Transit • Hints on handling and setting-up the transit • Pick up transit by leveling head and standards • When carrying the transit, have telescope locked in position perpendicular to the leveling head with objective lens down • When setting-up, keep tripod head level and bring plumb bob to within ¼” of point to be set over, then loosen leveling screws enough to enable you to movetransit on plate, then move transit until it is over the point

  36. Operation of Transit A B C • 9 Steps • Set up over point B and level it. Loosen both motions • Set up the plates to read 0 and tighten the upper clamp. (Upper and lower plates are locked together) • Bring Vernier to exactly 0 using upper tangent screw and magnifying glass. • Sight on point A and set vertical X-hair in center of point, by rotating transit • Tighten the lower clamp and entire transit is locked in • Set X-hair exactly on BS point A using the lower tangent screws. At this point the vernier is on 000’ and the X-hairs are on BS

  37. Operation of Transit A B C • Loosen the upper clamp, turn instrument to right until you are near pt. C. Tighten the upper clamp • Set vertical X-hair exactly on pt. C using the upper tangent screw. • Read  on vernier • If repeating , loosen lower motion and again BS on A (using only lower motion), and then loosen upper motion to allow  to accumulate. • If an instrument is in adjustment, leveled, exactly centered, and operated by an experienced observer under suitable conditions, there are only 2 sources for error. • Pointing the telescope • Reading the plates

  38. Transit Field Notes • Use longest side for backsite

  39. TOTAL STATIONS

  40. TOTAL STATION SET UP • WHEN TOTAL STATION IS MOVED OR TRANSPORTED, IT MUST BE IN THE CASE!!!!!!!! • ESTABLISH TRIPOD OVER THE POINT. • OPEN THE CASE AND REMOVE TOTAL STATION, PLACING IT ON THE HEAD OF THE TRIPOD AND ATTACH SECURELY WITH CENTER SCREW. • CLOSE THE CASE. • GRASP TWO TRIPOD LEGS AND LOOK THROUGH THE OPTICAL PLUMB, ADJUST THE LEGS SO THAT BULLSEYE IS OVER THE POINT (KEEP THE TRIPOD HEAD AS LEVEL AS POSSIBLE). • UTILIZING THE TRIPOD LEG ADJUSTMENTS, LEVEL THE TOTAL STATION USING THE FISH-EYE BUBBLE. • LOOSEN THE CENTER SCREW TO ADJUST THE TOTAL STATION EXACTLY OVER THE POINT IF NEEDED. • COMPLETE LEVELING THE TOTAL STATION USING THE LEVEL VIAL. • CHECK TO MAKE SURE YOU ARE STILL ON THE POINT.

  41. TURNING ANGLES WITH TOTAL STATION • SIGHT ON THE BACKSIGHT UTILIZING THE HORIZONTAL ADJUSTMENT SCREW. • ZERO SET THE INSTRUMENT (THIS PROVIDES AN INNITIAL READING OF 0 SECONDS. • LOOSEN TANGENT SCREW AND ROTATE INSTRUMENT TO FORESIGHT. • TIGHTEN TANGENT SCREW AND BRING CROSS HAIR EXACT ON TARGET WITH ADJUSTMENT SCREW. • READ AND RECORD ANGLE AS DISPLAYED. TO CLOSE THE HORIZON: • SIGHT ON FORESIGHT POINT FROM ABOVE AND ZERO SET INSTRUMENT. • ROTATE TO FORMER BACKSIGHT AND ADJUST INSTRUMENT TO EXACT. • READ AND RECORD ANGLE AS DISPLAYED. ANGLE FROM DIRECT AND INDIRECT SHOULD EQUAL 360 DEGREES.

  42. TOTAL STATION DISTANCE MEASUREMENT • POINT THE INSTRUMENT AT A PRISM (WHICH IS VERTICAL OVER THE POINT. • PUSH THE MEASURE BUTTON AND RECORD THE DISTANCE. YOU CAN MEASURE THE HORIZONTAL DISTANCE OR THE SLOPE DISTANCE, IT IS IMPORTANT THAT YOU NOTE WHICH IS BEING COLLECTED. • IF YOU ARE MEASURING THE SLOPE DISTANCE, THE ZENITH ANGLE MUST BE RECORDED TO ALLOW THE HORIZONTAL DISTANCE TO BE COMPUTED. • IF YOU ARE COLLECTING TOPOGRAPHIC DATA WITH ELEVATIONS, IT IS IMPORTANT THAT THE HEIGHT OF THE INSTRUMENT AND THE HEIGHT OF THE PRISM BE COLLECTED AND RECORDED. THIS CAN ALSO BE SOLVED BY SETTING THE PRISM HEIGHT THE SAME AS THE INSTRUMENT HEIGHT.

  43. TOTAL STATION RULES • NEVER POINT THE INSTRUMENT AT THE SUN, THIS CAN DAMAGE THE COMPONENTS OF THE INSTRUMENT AS WELL AS CAUSE IMMEDIATE BLINDNESS. • NEVER MOVE OR TRANSPORT THE TOTAL STATION UNLESS IT IS IN THE CASE PROVIDED. • DO NOT ATTEMPT TO ROTATE THE INSTRUMENT UNLESS THE TANGENT SCREW IS LOOSE. • AVOID GETTING THE INSTRUMENT WET, IF IT DOES GET WET, WIPE IT DOWN AND ALLOW TO DRY IN A SAFE AREA BEFORE STORAGE. • BATTERIES OF THE TOTAL STATION ARE NICAD AND THUS MUST BE CHARGED REGULARLY. AT LEAST ONCE PER MONTH, THE BATTERY SHOULD BE CYCLED. • CARE SHOULD BE TAKEN AT ALL TIMES, THESE UNITS ARE EXPENSIVE ($8,000 - $45,000)

  44. Angles and Determination of Direction • Angle – difference in direction of 2 lines • Another way of explaining is the amount of rotation about a central point • 3 kinds of Horizontal angles: Exterior ( to right); Interior; Deflection • To turn an angle you need • A reference line • Direction of turning • Angular distance • Angular Units • Degrees, minutes, seconds (sexagesimal system) • Circle divided into 360 degrees • Each degree divided by 60 minutes • Each minute divided into 60 seconds • Radians • 1 radian = 1/2 of a circle = 0.1592*360 = 5717’44. 8” • Grads (Centesimal System) – now called Gon • 1/400 of a circle or 054’00” (100 gon = 90)

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