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CE03 - Fundamentals Of Surveying > Lesson 3: Horizontal Distance Measurement > Flashcards

Lesson 3: Horizontal Distance Measurement Flashcards

1
Q

distance between any two
random points in 3D space

A

Spatial Distance

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2
Q
  • linear distance between two points on any surface
  • if points are at different elevations, distance is the horizontal length between plumb lines at the points
A

Horizontal Distance

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3
Q

Factors to be Considered in Choosing
Methods of Determining Horizontal Distances

A
  1. Purpose of the Measurement
  2. Required Accuracy
    * Rough reconnaissance ( 1 part in 100 )
    * First-order surveys (1 part in 1,000,000)
  3. Cost
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4
Q

Methods and Instruments Used to
Determine Horizontal Distances

A
  1. Pacing
  2. Tacheometry
  3. Graphical and Mathematical Methods
  4. Mechanical Devices
  5. Photogrammetry
  6. Taping
  7. EDM
  8. Global Positioning Systems
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5
Q
  • Consists of counting the number of steps in the required distance.
  • Furnishes a rapid means of approximately checking a more precise measurement of distance.
A

Pacing

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6
Q

Pacing is used on:

A
  • reconnaissance survey
  • small-scale mapping
  • locating details
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7
Q
  • defined as the length of a step
    in walking
    – 2 is equivalent to a stride
    or a double-step
    – Relative Precision: 1/200 to
    1/100 is seldom less than 1/300
A

Pace

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8
Q

How to Calibrate One’s Pace?

A

– walk at a uniform step along a line of known length on a level
ground and count the number of paces to cover the whole stretch
– compute the pace factor (in m/pace)

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9
Q

Factors Affecting Length of Pace:

A
  • Speed of pacing
  • Roughness of the ground
  • Weight of clothing and shoes
  • Fatigue on the part of the pacer
  • Slope of the terrain
  • Age and sex of the individual
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10
Q

Mechanical Pace Counters

A
  1. Pedometer
  2. Passometer
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11
Q

a pager-size device worn on the belt
that simply records the number of steps
made based on the body’s movement (hips)

A

Pedometer

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12
Q

registers the number of paces and
distances

A

Pedometer

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13
Q

registers a pace by impact
each time a foot touches the
ground

A

Passometer

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14
Q

about the size of a watch

A

Passometer

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15
Q
  • an indirect method of measuring horizontal
    distances
  • it is based on the optical geometry of the
    instruments used
  • uses subtended intervals and angles
    observed with a transit or a theodolite on a
    graduated rod or scale
  • relative accuracy is 1 part in 300 to 400
A

Tacheometry

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16
Q

Methods in Tacheometry

A
  1. Stadia Method
  2. Subtense Bar Method
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17
Q
  • uses a telescope with 2 horizontal cross hairs and a graduated rod.
A

Stadia Method

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18
Q

Precision of the stadia method depends on the ff:

A
  • Refinement with which
    instrument was manufactured
  • Skill of the observer
  • Length of measurement
  • Effects of refraction
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19
Q

is set up at a distant station while a
theodolite at the end of the line
measures the horizontal angle
subtended by the distance
between the two targets

A

Subtense Bar Method

20
Q

distances are determined geometrically

A

Graphical and Mathematical Methods

21
Q

Mechanical Devices

A
  • Odometer
  • Measuring Wheel
  • Optical Rangefinder
  • Mileage Recorder
22
Q

attached to a wheel for
purposes of roughly measuring
surface distances (speed)

Relative Precision:
1/200 on fairly level ground

Uses:
Route Location Surveys
Preliminary Surveys
Small-scale Mapping

A

Odometer

23
Q

an odometer except that it is a more portable and self-contained device

Use:
Determining distance along
irregular or curved lines and
boundaries

A

Measuring Wheel

24
Q

determines distances approximately by focusing

A

Optical Rangefinder

25
Q

attached to ordinary automobile speedometer

A

Mileage Recorder

26
Q
  • Measuring of images on a photograph
  • Uses scales to obtain ground distances
A

Photogrammetry

27
Q

Measurement of distance is based on the invariant speed of light or electromagnetic waves in a vacuum

A

Electronic Distance Measuring (EDM)
Equipment

28
Q

EDM Classification:

A
  1. Electro-optical
    e.g. Geodimeter
  2. Electromagnetic (microwave)
    e.g. Tellurometer
29
Q

Advantages of EDM

A
  • speed and accuracy
  • lightweight and portable
  • low power requirement
  • easy to operate
  • ease in measurement over inaccessible terrain
  • applicable to the measurement of both short and long lengths
  • automatically measures, displays and records needed data
  • slope measurements are internally reduced to horizontal and
    vertical components
  • automatically accumulates and averages readings for slope range, horizontal and vertical angles
30
Q
  • a combination electronic transit and
    electronic distance measuring device
    (EDM)
  • angles and distances from the
    instrument to points to be surveyed are
    determined
  • using trigonometry, angles and
    distances may be used to calculate the
    actual positions (x, y, and z or northing,
    easting and elevation) of surveyed
    points in absolute terms
A

Total Station

31
Q
  • involves direct measurement of distances with
    steel tapes
  • most common method of measuring or laying
    out horizontal distances
  • consists of stretching a calibrated tape between two points and reading the distance indicated on the tape
A

Taping

32
Q
  • by Sir Edmund Gunter (1620)
  • 66 ft with 100 links
  • 1 link = 0.66ft = 7.92 inches
A

Gunter’s Chain

33
Q

Types of Measuring Tapes

A
  1. Steel tape
  2. Metallic tape
  3. Non-metallic tape
  4. Invar tape
  5. Lovar tape
  6. Fiberglass tape
  7. Wires
  8. Builder’s tape
  9. Phosphor-bronze tape
  10. Nylon-coated steel tape
34
Q

 ribbon of steel
 0.5-1.0cm in width; weighs 0.8-1.5kg / 30 meters
 for most conventional measurements in surveying and
engineering works

A

Steel tape

35
Q

 aka woven tapes
 made of water-proof linen fabric
 woven longitudinally with small brass, copper or bronze
 reduce stretching, increase strength
 for short distances
 unsuitable for precise measurements and around electrical installations

A

Metallic tape

36
Q

 coated with plastic material
 reduce effects of moisture, humidity and abrasion
 safe to use when working around electrical
installations

A

Non-metallic tape

37
Q

 made of an alloy of nickel (35%) and steel (65%)
 with a very low coefficient of thermal expansion
(1/30 to 1/60 of steel tape)
 “Invariable”
 used for precise measurements
 10 times as expensive as steel
 easily bent and damaged

A

Invar tape

38
Q

 properties and costs between steel and invar tapes

A

Lovar tape

39
Q

 woven with fiberglass (longitudinal and transverse pattern)
 strong and flexible
 best used in vicinity of electrical equipment

A

Fiberglass tape

40
Q

 used before thin flat steel tapes
 still practical in hydrographic surveys

A

Wires

41
Q

 smaller cross sections and lighter than engineer’s tape
 graduated to suit commonly used dimensions in building constructions

A

Builder’s tape

42
Q

 rust-proof tape
 used in vicinity of salt water

A

Phosphor-bronze tape

43
Q

 flexible and crack-resistant
 steel core tape
 with coating of permanently bonded non-conducting
nylon
 designed to be resistant to corrosion and rust

A

Nylon-coated steel tape

44
Q

Taping Accessories

A
  • Tension Handle
  • Chaining Pins
  • Leather Thong
  • Range Pole
  • Clinometer
  • Plumb Bob
  • Wooden Stake
45
Q

Operations in Taping

A
  1. Breaking Tape
  2. Slope Taping
46
Q

measurement of shorter distances which are accumulated to total a full tape length

A

Breaking Tape

47
Q

taped measurements are made directly along the slopes when the ground is of uniform inclination and fairly smooth

A

Slope Taping

CE03 - Fundamentals Of Surveying (5 decks)

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