Distance Measurement

1
Distance Measurement

• Chapter 3 McCormacs 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 1/4s, 1/16s
• Chain 66 feet -gt 80 chains/mile
• 100 links -gt 0.66 ft/link 7.92
• 20 Ch, 16Lk 20.16 Ch 1330.6 feet
• Rod 16.5 feet -gt 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 1/100ths forward from 0
RC at 71, FC at 0.54, record 71 0.54 71.54
Cut Chain 1/100ths 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