- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2700) Unit Title: SURVEYING _____________________________________________________________________________ (CLF2702) Topic: Surveying Equipment Time Year(s) 3 Hours 1 / 2 / 3 / 4 _____________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will will be able to: Learning Outcome #: (O-3) - Set up and level an instrument and read a rod, ruler, or tape. (O-5) - Be able to demonstrate proper use of a hand level or clinometer. Special Materials and Equipment: Steel tape, chaining pins, range poles, plumb bob, odometer, tripod level, hand level (clinometer). References: Bowers, W., Jones, B. A., Jr., & Olver, E. F. (1973). Engineering Applications in Agriculture. Champaign, IL: Stipes Publishing Co. Kissam, Phillip. (1978). Surveying Practice (3rd ed.). New York: McGraw-Hill. Phipps, Lloyd J., & Reynolds, Carl L. (1990). MECHANICS IN AGRICULTURE (4th ed.). Danville, IL: Interstate Publishers. Evaluation: Quiz/test by instructor. Exercise to measure a field or building length accurately with a steel tape. Exercise to measure a field area using an odometer. Exercise to properly set up a tripod level. Exercise to read a level rod. Exercise to set contour lines on a hillside or to measure the slope of a hill. TOPIC PRESENTATION: Surveying Equipment A. Steel Tape 1. 100 foot long steel tape (sometimes called a "chain") is most commonly used to measure horizontal distances. a. Has an accuracy of 0.05 feet when used properly 2. Metallic cloth tapes or cloth tapes are also used however, they are generally not as durable or as accurate as steel tapes. 3. Tapes are graduated (marked) in feet and 10ths and 100ths of a foot along their length. 4. Care of the Steel Tape a. Prevent the formation of loops in the tape. If tension (pull) is applied to a looped tape, it can break or permanently kink. b. Loops can be prevented by always keeping a bit of pull on the tape such that no slack develops. c. For measurements of less than the full tape (100 feet), keep the tape on the reel. d. When using the full length of the tape off the reel, move it by dragging from one end only. e. When a tape is wet, clean and oil it as soon as possible. 5. Use of the Steel Tape a. Measuring the distance between two points (Point A to Point B) 1) Points A and B should be identified with a range pole or other such fixed marker (benchmark, corner of a building, etc.). 2) The head tapeman unreels the tape by walking toward point B while the rear tapeman holds the 100 foot end of the tape as near as possible over point A. 3) If the head tapeman reaches the end of the tape, the tape should be removed from the reel and a handle or thong attached to the end of the tape. 4) If the head tapeman reaches the end point of the tape before reaching point B, the head tapeman should stop and be "lined in." 5) The "lining in" process is directed by the rear tapeman to assure measurement along the line to be measured. 6) Using hand or verbal signals, the rear tapeman directs the head tapeman to near alignment with point B (which is still in the distance). At this time, the rear tapeman calls out "tape." The head tapeman then stoops, kneels to the left side of the tape and is more accurately "lined in" by the rear tapeman. 7) When the tape is on line, the rear tapeman kneels across the tape so that he can sight directly across it (at the "100 foot" reading) to point A. 8) The head tapeman should apply tension to the tape (usually 10 or 20 pounds of pull when using a spring gage). When the rear tapeman is centered over Point A (or a chain pin from a previous 100 foot measurement), he will call out "mark" or "right here" at which time the head tapeman will set a pin at the "0" mark of the tape. 9) When the head tapeman reaches point B before the end of the 100 foot tape, he stops and the rear tapeman comes up to the last pin that was set before Point B. The tapemen adjust the tape so that an even foot mark is opposite the rear tapeman's pin. 10) The tape is adjusted such that Point B is within the 0 to 1 foot section of the tape and an exact foot mark is held over the last pin before pin B. The head tapeman pulls tension on the tape and reads the tape to 10ths or 100ths as desired. 11) The number read by the head tapeman is subtracted from the foot reading being held by the rear tapeman. If the rear tapeman is aligning the 28 foot line over the last pin and the head tapeman reads 0.44 feet, then a subtraction gives the last distance as 28.00 - 0.44 = 27.56 feet. B. Chaining Pins 1. These are steel wire pins about 12 inches long, sharpened on one end and looped at the other end. 2. They are used to mark off exact measurement points along a measured line. C. Range Poles 1. They are normally about 8 foot long and painted alternately red and white for visibility. 2. Range poles are used to mark the two end points of a line to be measured. D. Plumb Bob 1. This is a conical piece of metal hung from a string. 2. It is used to assist in measuring true horizontal distance on uneven terrain. This is done by hanging the plumb bob string over the tape (after the tape has been stretched to be level horizontally) and allowing the plumb bob tip to touch the ground to mark the point of measurement or reference. E. Odometer 1. This is a wheel-like device (normally the diameter of a child's bicycle wheel) with a push handle and a revolution counter which is used to measure horizontal distance. 2. On smooth, horizontal surfaces, this device can measure horizontal distances to within 1%. a. It is not normally recommended for use for accurate measurement on rough ground or across heavy vegetation. 3. The odometer measures distance by counting the number of revolutions of a wheel of known circumference. a. The horizontal distance measured in feet is equal to 3.1417 times the number of revolutions of the wheel when traversing the line to be measured multiplied by the diameter of the wheel in feet. 4. Using the Odometer to Measure Distances a. Set the odometer at the starting point of the line to be measured in such a way that the counter is just beyond the point where it makes the first count. b. Set the odometer back to a zero count reading. If the counter cannot be zeroed, record the reading on the counter. c. Begin to roll the odometer along the line to be measured at a normal walking pace. d. Stop at the end of the line to be measured and record the counter reading. e. If started from a counter reading of zero, the final reading will be the net count number and will be used to compute the measured distance. Otherwise, subtract the final reading from the initial counter reading and this number will be the net counter number to compute the measured distance. If the odometer has a conversion scale, use this to convert the net count number to the distance measured. Otherwise, multiply the net count number times 3.1417 times the diameter of the odometer wheel in feet to obtain the distance measured in feet. F. Tripod Level 1. This is a high-powered telescopic sight with a sensitive spirit level attached to it; it is adjusted so that when the bubble is centered, the line of sight is level. 2. Uses of a Tripod Level a. Differential leveling b. Profile leveling 3. Components of a Tripod Level a. Telescope b. Three or four leveling screws c. Leveling plate and head for fastening the level firmly to the tripod d. Tripod 4. Setup of the Tripod Level a. Spread the legs of the tripod three to four feet apart and push them individually and firmly into the ground. b. Adjust the tripod such that the leveling head (head plate) is approximately level and the telescope is near eye height. Tighten the thumb nuts on the legs to provide rigidity. c. Mount the level to the headplate by screwing it down. d. Loosen the telescope clamp and swing the telescope barrel directly over two of the leveling screws. e. Adjust these leveling screws by tightening one and loosening another simultaneously in order to center the bubble in the bubble tube. 1) This is best accomplished by moving the thumbs together to move the bubble one way and by moving the thumbs away from one another to move the bubble the other way. The bubble will follow the direction of movement of the left thumb. f. Turn the telescope over the other pair of leveling screws and repeat the process in order to level the bubble. g. Since the process of leveling over one set of leveling screws will affect the level over other screws, the process must be repeated several times over each combination of leveling screws. When level, the bubble will stay level or nearly level throughout a complete 360§ rotation of the telescope. h. Look through the telescope and focus the cross hairs by adjusting the eye piece with a rotary sliding motion. i. Focus on the level rod by turning the objective focus knob. j. Check the bubble tube immediately before and after each rod reading. Make any necessary adjustment before the reading is considered correct. k. Stand in one position as much as possible when making readings. Stand between the legs of the tripod rather than straddling them; avoid kicking or bumping into the tripod legs. G. Leveling Rod 1. This is a wooden rod graduated upward from zero at the bottom. It is the tool used to measure distance from the reference plane (at the bottom of the level rod) to the line-of-sight through the level. a. The rod is graduated to feet, 10ths of a foot, and 100ths of a foot. b. The level rod may or may not have a target for use in making readings. 2. A self-reading rod is commonly used and does not have a target. The readings can be taken directly from the person looking through the level telescope. 3. Reading the Level Rod a. Whole feet are delineated by the longest pointed markings on the rod that point at large red numbers. b. The 10ths and 100ths are indicated by smaller divisions between the foot markings. c. Each 10th of a foot division is delineated by a shorter pointed marking as well as by a black number. The exact reading is read at the flat edge of the sharp point. d. Each 100th of a foot division is delineated by alternating black and white markings between the 10th markings. The 100th values are read at the edge of the black or white line, i.e., each marking is 1/100th of a foot wide. Note to Instructor: Consult previously cited references or any basic surveying textbook for diagrams of a level rod. 4. Using the Level Rod with the Level a. The person handling the level rod is known as the rodman, whereas the person using the level is the instrument man. b. The rodman must hold the rod in an exact vertical position or the rod will give an incorrect distance from line-of-sight to the point being measured. c. The rod should be held lightly, with the fingers on the edge of the rod. Holding the elbows firmly against the ribs will help to stabilize the rod. H. Hand Level or Clinometer 1. This is a hand-held device used to make less accurate surveying measurements and estimates. 2. Its components are: a. A sighting tube with a horizontal cross hair to mark the line-of- sight b. A bubble tube c. A small mirror to show a reflection of the bubble through the eyepiece d. Note: When the reflection of the bubble is centered on the horizontal cross hair, the line of sight is horizontal. 3. Uses of a Hand Level or Clinometer a. Used with a level rod to measure slopes b. Used with a board that is marked for locating contour lines 4. Use of a Hand Level with a Level Rod to Measure Slopes a. The level person stands halfway down the slope to be measured. b. The rodman stands approximately 50 feet upslope from the level person with the level rod in the appropriate position. c. The level person sights through the hand level, achieves a horizontal line-of-sight on the level rod and records the reading on the level rod (see procedures in paragraph G-3 above). d. With the level person remaining in the same location, the rodman moves exactly 100 feet down the slope and sets the level rod. e. The level person turns around and repeats step c. above. f. The slope (in percent) is equal to the numerical difference in the two readings. For example: 1) The upslope reading on the level rod is 3.7 feet. 2) The downslope reading on the level rod is 9.9 feet. 3) The distance between the measured points is 100 feet. 4) The slope is 9.9 - 3.7 = 6.2%. 5. Use of the Hand Level to Locate Contour Lines a. A contour line is a line of equal elevation (height) on the earth's surface. More commonly, a contour line is thought of as a line of equal elevation around a hillside. Cattle trails that appear to go horizontally around a hill can be thought of as crude representations of contour lines. b. Locating contour lines can be useful in laying out terraces, guides for tillage operations in contour farming, or laying out the centerline for a roadway around a hillside. c. Procedure: 1) Initially, the level person determines his or her eye height by sighting on a mark on the level rod, a mark on a board, or a feature or mark on the rodman. 2) The initial point on the contour line is selected and the level person stands at this location. 3) The rodman moves 50 to 100 feet along the approximate contour line. 4) The rodman is directed up or down the slope by the level person sighting through the hand level at the chosen mark (on the level rod, board, or rodman). 5) When the cross hairs are aligned with the mark and the bubble, the level person is on the contour line and should drive a stake at this location. 6) The rodman should remain by the stake just driven and the level person should move ahead on the approximate contour line to approximately 50 to 100 feet beyond the rodman. 7) The level person then sights back to the rodman and moves himself up or down the slope until the cross hairs again line up with the chosen mark on the rodman. At this point, the level person is on the contour line and should drive in a stake. 8) The rodman then leapfrogs past the level person as before and the procedure is repeated until the entire contour line has been located. 7/12/91 JR/tf #%&C