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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

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
attached to ordinary automobile speedometer
Mileage Recorder
26
* Measuring of images on a photograph * Uses scales to obtain ground distances
Photogrammetry
27
Measurement of distance is based on the invariant speed of light or electromagnetic waves in a vacuum
Electronic Distance Measuring (EDM) Equipment
28
EDM Classification:
1. Electro-optical e.g. Geodimeter 2. Electromagnetic (microwave) e.g. Tellurometer
29
Advantages of EDM
* 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
- 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
Total Station
31
- 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
Taping
32
- by Sir Edmund Gunter (1620) - 66 ft with 100 links - 1 link = 0.66ft = 7.92 inches
Gunter’s Chain
33
Types of Measuring Tapes
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
 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
Steel tape
35
 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
Metallic tape
36
 coated with plastic material  reduce effects of moisture, humidity and abrasion  safe to use when working around electrical installations
Non-metallic tape
37
 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
Invar tape
38
 properties and costs between steel and invar tapes
Lovar tape
39
 woven with fiberglass (longitudinal and transverse pattern)  strong and flexible  best used in vicinity of electrical equipment
Fiberglass tape
40
 used before thin flat steel tapes  still practical in hydrographic surveys
Wires
41
 smaller cross sections and lighter than engineer’s tape  graduated to suit commonly used dimensions in building constructions
Builder’s tape
42
 rust-proof tape  used in vicinity of salt water
Phosphor-bronze tape
43
 flexible and crack-resistant  steel core tape  with coating of permanently bonded non-conducting nylon  designed to be resistant to corrosion and rust
Nylon-coated steel tape
44
Taping Accessories
- Tension Handle - Chaining Pins - Leather Thong - Range Pole - Clinometer - Plumb Bob - Wooden Stake
45
Operations in Taping
1. Breaking Tape 2. Slope Taping
46
measurement of shorter distances which are accumulated to total a full tape length
Breaking Tape
47
taped measurements are made directly along the slopes when the ground is of uniform inclination and fairly smooth
Slope Taping

CE03 - Fundamentals Of Surveying (5 decks)

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