Horizontal and Vertical Distance Flashcards
(94 cards)
1
Q
Horizontal Distance
A
Distance by Measurement
Distance by Mechanical Device
Distance by Electronic Distance Measurement
2
Q
Distance by Measurement
A
- Pacing
- Taping
- Tachymetry
3
Q
Length of step in walking
A
Pacing
4
Q
Length of one’s pace
A
Pace Factor-
5
Q
Pacing Relative Precision
A
1/200
6
Q
Most common method of measuring or laying out of horizontal distances.
Measured by stretching a calibrated tape between two points and reading distance indicated on the tape.
A
Tape
7
Q
Relative Precision of Taping
A
1:1000 to 1:25000
8
Q
Based on optical geometry
A
Tacheometry
9
Q
Determining horizontal distance
Precision depends on instrument, skills of the observer, length to be measured, parallax and refraction
Used in the topographic survey
A
Stadia Method
10
Q
Precision of Stadia Method
A
1/300 and 1/1000
11
Q
Stadia Method Formula:
A
D=Ks+C
Where:
K= Stadia Interval Factor (100)
s= stadia interval (upper-lower reading)
C= stadia constant (distance from the center of the instrument to the principal focus) value: 0
12
Q
How long is Subtense bar
A
= 2 meters long
13
Q
Subtense Bar Method
A
D= (𝑆/2)/tan〖𝛼/2〗
S= 2.0 m
D= 1/tan〖𝛼/2〗 or cot𝛼/2
14
Q
Distance by Mechanical Device
A
- By Odometer
- By Measuring Wheel
- Optical Rangefinder
15
Q
Measuring the number of revolution of the wheel
A
By Odometer
16
Q
Odometer Precision
A
1/200
17
Q
Similar to odometer except more portable and self
Contained
A
By Measuring Wheel
18
Q
Uses single-lens reflex camera
A
Optical Rangefinder
19
Q
Precision of Optical Rangefinder
A
1/50 for distance less than 500 meters
20
Q
Distance by Electronic Distance Measurement
A
- Geodimeter
- Tellurometer
21
Q
Very careful measurement in determining the interval of time between emission and reception of transmitted waves.
A
Electronic Distance Measurements
22
Q
Basic Principle: Linear Distance are based time required for radio or light wave to travel from one end of a line to the other.
A
a. Electro-Optical Instruments
b. Microwave Instruments
23
Q
Instrument that transmit wavelength within the visible spectrum
A
Electro-Optical Instruments
24
Q
- Transmit microwave corresponding to wavelengths of about 1.0 to 8.6 mm.
A
Microwave Instruments
25
Projects a pulsating visible light beam to a reflector which returns the light to the instrument.
Geodetic Distance Meter
26
Utilize a high frequency microwave transmission
distance can be computed on the basis of velocity of radio waves
Tellurometer
27
Precision of Geodetic Distance Meter:
1/200,000
28
Precision of Tellumeter:
1/300,000
29
- surveyor’s or engineer’s tape
- Most common: 30 meter tape
Steel Tapes
30
- Tapes woven from synthetic materials with strong dimensional stability.
- Use when working on electrical installation
Non-metallic tapes
31
LIST OF Measuring Tape
SNILFW
1. Steel Tapes
2. Non-metallic tapes
3. Invar Tapes
4. Lovar Tape
5. Fiberglass
6. Wires
32
Invar Tapes are made of how many percent of alloy nickel?
35%
33
Invar Tapes are made of how many percent of Steel?
65%
34
Properties and costs somewhere between the conventional steel tapes and invar tape.
Lovar Tape
35
Made of fiberglass in a longitudinal and transverse pattern
Fiberglass
36
Flat steel tape utilized in measuring lengths.
Wires
37
Measurement directly along the slopes when the ground is of uniform inclination and fairly smooth.
Slope Taping
38
List Corrections
TPS
Corrections Due to Temperature
Corrections Due to Pull
Corrections Due to Sag
39
Tape Correction - TOO LONG
Measuring - ADD
Layout - SUBTRACT
40
Tape Correction - TOO SHORT
Measuring -SUBTRACT
Layout - ADD
41
Tape Correction
Corr = TL-NL
42
Vertical Distance
1. Leveling
2. Level Surface
3. Level Line
4. Horizontal Surface
5. Horizontal Line
6. Vertical Line
7. Mean Sea Level
8. Geoid
9. Datum
10. Elevation
11. Difference in Elevation
43
Directly or indirectly measuring vertical distances to determine the
elevation of points or difference in elevation.
Leveling
44
Leveling Used in:
1. Engineering design
2. Construction
3. Production of topographic map
44
Leveling Used in:
1. Engineering design
2. Construction
3. Production of topographic map
45
Curved surface which any point perpendicular to the direction of gravity or plumb line
Level Surface
46
Curved line in a level surface all points of which are normal to the direction of gravity and equidistant from the center of the earth.
Level Line
47
Plane tangent to a level surface at a particular point
Horizontal Surface
48
- Straight-line in a horizontal plane which is tangent to a level line at one point.
- Perpendicular to the direction of gravity at the point of tangency
Horizontal Line
49
-line parallel to the direction of gravity.
Vertical Line
50
- Imaginary surface of the sea which is
midway between high and low tides.
- Reference surface to which most
ground elevations are referred.
Mean Sea Level
51
How to determine Mean Sea Level?
Averaging the height of the sea’s surface for all its tide stages over a long period of time which may extend to about 20 years
52
The state of gravitational equilibrium.
Mean Sea Level
53
The model of the global mean sea level.
Geoid
54
Convenient level surface parallel to the mean sea level to which elevations of a particular are referred.
Datum
55
Abstract coordinate system with a reference surface (such as sea level) that serves to provide known locations to begin surveys and create maps.
Geodetic datum
56
Vertical Distance above or below mean sea level
Elevation
57
Above mean sea level
Positive Elevation
58
Below mean sea level
Negative Elevation =
59
Vertical distance between the two level surfaces in which the point lie.
Difference in Elevation
60
Errors in Leveling
IPN
1. Instrumental Errors
2. Personal Errors
3. Natural Errors
61
Imperfection in the instruments either from faults in their manufacturers or from improper adjustments
Instrumental Errors
62
List of Instrumental Errors
IRD
a. Instrument out of Adjustment
b. Rod Not Standard Length
c. Defective Tripod
63
- leveling being out of adjustments
- error will gently minimized or eliminated if the backsight and foresight distance are kept nearly equal.
Instrument out of Adjustment
64
-inaccurate graduations or divisions on a rod which may introduced systematic errors
Rod Not Standard Length
65
Effect of Rod Not Standard Length
Effects: incorrect markings on the tape.
66
Movement of the level due to setting of the tripod legs.
Defective Tripod
67
* Limitations of senses, skills, training and teamwork
* Erroneous manipulation
Personal Errors
68
List of Personal Errors
BPFRIU
a. Bubble Not Centered
b. Parallax
c. Faulty Rod Readings
d. Rod not Held Plumb
e. Incorrect Setting of Target
f. Unequal Backsight and Foresight Distances
69
Datum that Fit in a certain region.
Local Datum
70
Datum that fit worldwide.
Earth-centered datum.
71
- bubbles is not centered in the level vial
Bubble Not Centered
72
How to fix the problem, bubbles is not centered
The instrument should not be unnecessarily handled.
73
- slightly divergent value could be res.
-relative displacement b/w image focusing lens.
Parallax
74
-misreading number in meters and decimals when taking rod readings.
Faulty Rod Readings
75
- Instruments are equipped with 3 horizontal hairs
- 3 reading are usually recorded.
Note:
the difference between the middle and lower readings =difference between middle and upper readings.
Precise Levelling
76
- rod not held as nearly vertical as possible.
Rod not Held Plumb
77
What if foresight are consistently greater than backsights?
= errors will be cumulative
78
not handle levelling rod carefully
Incorrect Setting of Target
79
Make backsight and corresponding foresight distance nearly equal
Unequal Backsight and Foresight Distances
80
Effects of Unequal Backsight and Foresight Distances.
Error due to imperfect adjustments and error due to curvature and refraction are reduced or totally eliminated.
81
How to balance Foresight and Backsight?
- taping, pacing, or stadia measurement
82
Could not be totally removed but their effects can be reduced by applying corrections
Natural Errors
83
Can occur in long sights and when backsights and foresights are not equal.
Curvature of the Earth
84
Curvature error
.07/100 meters
85
List of Natural Errors
a. Curvature of the Earth
b. Atmospheric Errors
c. Temperature Variations
d. Wind
e. Settlement of Instruments
f. Faulty Turning Point
86
- Fluctuating refraction in the atmosphere.
- Likely because heatwaves are present making the rod unsteady when sight is taken.
Atmospheric Errors
87
How to be avoid Atmospheric Errors?
Short distances.
88
Can be neglected or is negligible
Ordinary Leveling
89
Combined corrections for curvature and refraction are applied to observed rod readings.
Precise Leveling
90
Level rods either expand or contract.
Temperature Variations
91
Shakes a leveling instrument making it difficult to center the bubble in
the level vial.
Wind
92
Cumulative since every settlement of the instrument increase the
computed elevations of all error observed points by the amount of
settlement.
Settlement of Instruments
93
- Differential leveling work
- source of error
- settlement of instrument
- cumulative type
Faulty Turning Point
