INTRODUCTION TO DISTANCE MEASUREMENT
HORIZONTAL DISTANCE MEASUREMENT
In plane surveying, the distance between two points means the horizontal
distance.
If the points are at different elevations, then the distance is the
horizontal length between plumb lines at the points.
METHODS OF MEASURING HORIZONTAL DISTANCES
Pacing -- accuracy 1 / 100 (1.0%)
Tacheometry (stadia) -- accuracy 1 / 500 (0.2%)
Taping -- accuracy (Standard) 1 / 5,000 (0.02%)
Electronic Distance Measurement (EDM) -- accuracy 1 / 1,000,000 (0.0001%)
Definition: Applying a known length of tape to a line
HISTORICAL TAPING EQUIPMENT
Poles
constructed of wood or metal
length of one rod (16.5 ft)
Gunter's Chain
66 ft
100 links, 1 link = 0.66 ft = 7.92 in
Engineer's Chain
100 ft
100 links, 1 link = 1 ft
Wires
metal coils with tabs for measuring distances
CURRENT TAPING EQUIPMENT
Surveyor's and Engineer's Steel Tapes
Standard lengths 100, 200, 300, and 500 ft
30, 60, 100, and 150 m
Other Tapes
-
Builder's Tapes -- common construction tape measures, usually marked in
feet and inches
-
Cloth Tapes -- inexpensive linen with fine copper wires for strength, not
for precise work
-
Fiberglass Tapes -- inexpensive flexible tapes wound on a reel, used like
steel tapes
-
Invar Tapes -- made of 35% nickel/65% steel and do not expand as much as
steel with heat, but are 10X more expensive than steel tapes
-
Lovar Tapes -- has properties and cost between steel and invar tape
-
Special-Purpose Tapes
TAPING ACCESSORIES
Chaining/Taping Pins -- used to mark tape lengths, especially when it is
required to "break tape" or when measuring over 100 feet, usually painted
red and white
Hand Level -- helps to keep tape level over sloping or uneven ground
Tension Handles -- helps you to hold on to tape when pulling it taut
Pocket Thermometer -- helps you figure expansion and contraction of tape
due to temperature
Range Poles -- long poles used to mark points over long distances to help
keep tape aligned properly
Plumb Bobs -- help you locate tape directly over point being measured
CARE OF EQUIPMENT
Always make sure you transport and store all surveying equipment, including
tapes, properly, and be familiar with their use
Steel Tapes
Don't kink
Don't pull around corners
Don't run over it
Wipe off and oil every day
Cloth Tapes
Don't cut the tape through misuse
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