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CIVE1260 Engineering Surveying and Construction Technology > Engineering Surveying Week 1 > Flashcards

Engineering Surveying Week 1 Flashcards

1
Q

What is engineering surveying?

A
  • “Geomatics” which is the science and study of spatially related info
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2
Q

What 6 activities does Geomatics cover?

A
  1. Hydrographic surveying
  2. Remote sensing
  3. Cartography and visualisation
  4. Photogrammetry
  5. Geographic information systems (GIS)
  6. Engineering surveying
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3
Q

What are the 3 fundamentals of engineering surveying?

A
  1. Heights
  2. Distances
  3. Angles
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4
Q

What are the units for height, distance, and angle?

A

Height: mm or m
Distance: mm or m
Angle: Degrees, minute, seconds (d,m,s)

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5
Q

How many minutes are in a degree?

A

60 ‘

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6
Q

How many seconds are in a minute?

A

60 ‘’

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7
Q

Convert 360 degrees to radians and gradians

A
  • 2π
  • 400g
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8
Q

What is 1 hectare in m2?

A

10000 m2

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9
Q

What is the plane of collimation?

A

The horizontal plane used to read the staff in levelling

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10
Q

What is a datum?

A

Known/assumed level to which the measured heights are referenced

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11
Q

What is reduced level?

A

RL is the height of a point relative to the chosen datum

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12
Q

What is the Ordinance datum?

A

Mean sea level at Newlyn Cornwall (Datum for Great Britain)

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13
Q

What are the different types of bench marks?

A
  • Temporary Bench Marks (TBMs)
  • Transferred Bench Marks (TBMs)
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14
Q

If a TBMs level is assumed, what type of bench mark is it?

A

Temporary bench mark

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15
Q

If TBM is levelled from an OSBM or GNSS point what type of benchmark is it?

A

Transferred bench mark

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16
Q

What is a HPC?

A

The height of the plane of collimation

17
Q

What is the level line?

A

One which at all points are normal to the direction of gravity as indicated by a plumb bob

18
Q

What is the horizontal line and how does it interact with the level line?

A
  • One which is normal to the direction of gravity at one point only
  • For distances up to 100m, these two lines are assumed to coincide
19
Q

What are the two types of optical level?

A
  • Automatic level
  • Digital level
20
Q

What are the similarities between the two types of optical levels?

A
  • They each have a telescope
  • They each have a levelling system
21
Q

What are the eight features of an automatic level?

A
  1. Base plate
  2. Foot screw
  3. Pond bubble
  4. Eyepiece (HAS CROSS HAIR)
  5. Focusing screw
  6. Tangent screw
  7. Horizontal circle
  8. Object lens
22
Q

What three elements does a levelling system have?

A
  1. 3 footscrews
  2. A pond bubble
  3. A suspended compensator
23
Q

How do you eliminate parallax when levelling?

A
  • Move eye up and down while looking into the eyepiece
  • If the image does not appear to move there is no parallax
24
Q

Give all the information you know about the levelling staff?

A
  • Telescopic - up to 5m, in several sections
  • Graduated to 10mm
  • Read by estimation to nearest 1mm
  • To ensure the staff is vertical is should be “rocked.” The minimum reading will occur when the staff is vertical and this is the reading that should be taken
25
Q

What is the back sight (BS)?

A
  • First reading taken after an instrument is setup
  • First BS must be to an OSBM or TBM
26
Q

What is a fore sight (FS)?

A
  • Last reading taken before an instrument is moved
  • Last FS must be an OSBM or TBM
27
Q

What is an intermediate sight (IS)?

A
  • Any reading which is not a BS or FS
28
Q

What is a change point (CP)?

A
  • Staff position to which both a FS and BS are taken
  • A “CP” denotes a movement of the instrument
29
Q

What are the three sources of error in levelling?

A
  1. Collimation error
  2. Parallax: Image and X-hairs not focused properly
  3. Staff and tripod defects
30
Q

What is collimation error and how is it detected?

A
  • Caused by badly adjusted compensator
  • Detected using the “Two peg test”
31
Q

How do you calculate collimation error?

A
  • Collimation error = True height difference - Apparent height difference
  • Where:
  • True height difference = S1 - S2
  • Apparent height difference = S3 - S4
  • Answer could be:
  • e = -0.004m per 60m (THE DISTANCE USED IS BIGGEST IN QUESTION)
  • e can be + or -
32
Q

How do you know if you need to adjust instrument for collimation error?

A
  • If e ≤ 1mm per 20m, do not need to adjust
  • If e > 1mm per 20m, you must adjust the instrument
33
Q

What are the other sources of errors in levelling?

A
  • Field or On-Site errors
  • e.g staff not vertical, unstable ground, mishandling instruments, instrument not level, windy or hot conditions
34
Q

How do you calculate allowable misclosure?

A

5 * n½

35
Q

How do you calculate actual misclosure?

A

Calculated reduced level - Measured reduced level

(IF THIS IS OUTSIDE ALLOWABLE MISCLOSURE, do not distribute error)

CIVE1260 Engineering Surveying and Construction Technology (5 decks)

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