Topic 4: Distance Measurement

Question 0

Distance measurement methods

Answer 0

Pacing
Odometers & wheels
Stadia
Taping or chaining
Electronic distance measurement (EDM)
Satellite systems (GPS)

Question 1

Pacing

Answer 1

Defined as one step.
Quick method for measuring distance or check a precise measurement (steel tape) 
A stride = 2 paces
Normal steps are needed:
   - you take shorter steps uphill.
   - you take longer steps downhill
With practice accuracy ratio is: 
1/50 -> 1/200

Question 2

Odometers & Measuring Wheels

Answer 2

A device that has a counter attached to it.

Good for measuring curves.

Question 3

Taping Equipment

Answer 3

Range Poles
Chain pins (taping)
Plumb bobs
Tapes

Question 4

General Taping Procedure

Answer 4

Clear line
Lay out tape on the ground, no kinks
Apply tension
Use plumb bobs or vertical angles for uneven ground
Read tape

Question 5

Taping along sloping ground: 3 methods

Answer 5

Tape may be held horizontally using plumb bobs
Tape may be held along the slope, slope distance, and correction made to get horizontal distance.
Tape may be held along the slope, need vertical angle.

Question 6

Horizontal Taping on Slope Ground

Answer 6

Both or one person must use plumb bob.
Precision 1/2500 - 1/3000
Hold tape more than 5 feet is difficult, wind my take over.
Use hand level

Question 7

Slope Taping

Answer 7

Quicker than horizontal taping
Eliminates plumb
Usually used with smooth slopes
Necessary to determine difference in elevation between ends of the tape to get vertical angle.

Question 8

Common Taping Errors

Answer 8

Incorrect tape length-systematic error
Temperature Variation-systematic/random error
Inconsistent tension-systematic/random error
Sag-systematic/random
Tape not horizontal-systematic/random
Improper plumbing-random error

Question 9

What is the standards for a 100 foot steel tape.

Answer 9

68 degrees F
10 lb pull
Tape fully supported

Question 10

Distance calibration Base Lines

Answer 10

National Geodetic Survey
Distance between the monuments
Accuracies approaching 1/1,000,000

Question 11

Slope Correction

Answer 11

A tape length S is stretched a long a slope. It is desired to determine the horizontal distance H.

Need either the slope angle or the vertical distance.

H=Scosx
Where x = slope angle

Question 12

Slope Grade

Answer 12

Grade % = (Vertical Rise/Horizontal distance) x 100%

Question 13

Measuring vs. Laying out a Distance

Answer 13

Measuring refers to determining the distance between two fixed points.
Laying out means establishing two points at a specified distance.

The correction depends on if is measuring or laying out!!!!!