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Distance Measurement

Distance Measurement. Chapter 3 – McCormac’s 5 th. Historical Measurement. Early Survey Crews Crew Chief Crew of 2 or 3 Brush Hogs Support Equipment Compass Chain – see page 42. Units of Measure. Mile = 5280 feet Divide into 1/4’s, 1/16’s Chain: 66 feet -> 80 chains/mile

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Distance Measurement

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  1. Distance Measurement Chapter 3 – McCormac’s 5th

  2. Historical Measurement • Early Survey Crews • Crew Chief • Crew of 2 or 3 • Brush Hogs • Support • Equipment • Compass • Chain – see page 42

  3. Units of Measure • Mile = 5280 feet • Divide into 1/4’s, 1/16’s • Chain: 66 feet -> 80 chains/mile • 100 links -> 0.66 ft/link = 7.92” • 20 Ch, 16Lk = 20.16 Ch = 1330.6 feet • Rod: 16.5 feet -> 4 rods/Ch, 320 rods/mi • Engineers Chain – 100 feet • Note Units – 10th, 100th of feet

  4. Methods of Measurement • Indirect • Subtense Bars – pages 39-40 • Stadia – Chapter 14 • EDM – Chapter 5 • Direct • Pacing • Odometers/Wheels • Taping or Chaining

  5. Pacing (1/50) • Try for natural pace • Measure a known distance • Pace a number of times, Average • Determine: • Length of Pace – nearest 0.1’ • Number of Paces in 100’

  6. Pacing Example • Measured length = 215.0’ • Pace 4 times – 74, 74, 75, 74 paces • Average no. of paces = 74.25 • Length of pace = 215’/74.25 paces= 2.9’/pace • Paces per 100’ = 100’/2.9’/pace= 34.5 paces

  7. Taping or Chaining • Equipment Needed • Tape • Steel • Fiberglass • Cloth • Tensiometer • Plumb bob • Hand level • Range Poles

  8. Chaining Process • Slope Chaining • Measure along slope • Convert to horizontal • Plumb Chaining • Measure with chain horizontal • Downhill, when possible • “Breaking” chain • Forward Chainer (FC) reads 1/100ths • Rear Chainer (RC) reads feet

  9. Add vs. Cut Chains Add Chain – 1/100th’s forward from 0 RC at 71, FC at 0.54, record 71 + 0.54 = 71.54’ Cut Chain – 1/100th’s back from 0 RC at 72, FC at 0.46, record 72 - 0.46 = 71.54’

  10. Chaining Process • Establish Line • Level chain • Tension • RC – sets full foot, calls “Mark” • FC – sets 1/100ths, calls “Mark” • RC calls feet – “86” • FC – calls portion – “Point 23” • RC repeats – “86.23”

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