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CIV 208
SURVEYING
WEEK 4: Leveling-Theory, Methods, Equipment (Chp
...
5)
Prof
...
Darçın AKIN
Gediz University
Faculty of Engineering and Architecture
Department of Civil Engineering
1
CIV 208: Week-4
Chp 4: Leveling-Theory, Methods and Equipment
2
CIV 208: Week-4
4
...
It is a vital
operation in
producing
necessary data for
mapping,
engineering
design, and
construction
...
(2) Lay out construction projects according to planned
elevations,
(3) Calculate volumes of earthwork and other materials,
(4) Investigate drainage characteristics of an area,
(5) Develop maps showing general ground configurations,
(6) Study subsidence and crustal (tectonic) motion of the
Earth
...
9
CIV 208: Week-4
10
CIV 208: Week-4
4
...
Level surface: A curved
surface that at every
point is perpendicular to
the local plumb line
...
11
CIV 208: Week-4
4
...
Vertical datum: Any level
surface to which
elevations are referenced
...
12
CIV 208: Week-4
Benchmark (BM): A relatively permanent
object, natural or artifical, having a marked
point whose elevation above or below a
reference datum is known or assumed
...
Vertical Control: A series of benchmarks or
other points of known elevations
established troughout an area
...
4 Curvature and Refraction
From the definitions of a level surface and a horizontal line, it
is an evident that a horizontal plane departs from a level
surface because of curvature of the Earth
...
0785 𝐾 2
𝐶 𝑚 : The departure of a level surface from a horizontal line
K: Distance in kilometers
14
CIV 208: Week-4
Since points A and B are on a level line, they have the same
elevation
...
15
4
...
5
...
This
method is used to measure
depths of mine shafts, to
determine floor elevations in
condominium surveys, and in
the layout and construction of
multistory buildings, pipelines,
etc
...
CIV 208: Week-4
17
4
...
1 Measuring Vertical Distances By Taping
or Electronic Methods
CIV 208: Week-4
• In
certain
situations,
especially on construction
projects,
reflectorless
electronic
distance
measurement (EDM) devices
are replacing the tape for
measuring vertical distances
on construction sites
...
5
...
A horizontal line of side within the
telescope is established by means of a level vial or
automatic compensator
...
5
...
Assume the
elevation of BM rock is known to be 820
...
After levelling the
instrument, a plus sight taken on a rod held on the BM gives a reading of
8
...
A plus sight (+S), also termed backsight (BS) is the reading on a rod
held on a point of known or assumed elevation
...
Adding the plus side to the
elevation BM rock, 820
...
42 ft
21
CIV 208: Week-4
If the telescope is then turned to bring into view a rod held on
point X, a minus sight (-S), also called foresight (FS), is
obtained
...
20 ft
...
Subtracting the minus sight, 1
...
42 gives
the elevation from point X as 827
...
HI= elev (BM) + BS
elev (X) = HI – FS
HI=820
...
42=828
...
42-1
...
22 ft
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CIV 208: Week-4
23
4
...
3 Barometric Leveling
CIV 208: Week-4
The barometer can be used to find relative elevations of
points on the Earth’s surface since a change of
approximately 1000 ft (300 mt) in elevation will
correspond to a change of about 1 in (2
...
24
4
...
4 Trigonometric Leveling
CIV 208: Week-4
The difference in elevation between two points
(1) The inclined or horizontal distance between them
(2) The zenit angle or the altitude angle to one point from
the other
...
144260253
27
CIV 208: Week-4
Example
The slope distance and zenith angle between A and B
were observed with a totalstation instrument as 9585
...
If the elevation of A is 1238
...
(HI is assumed equal to rB)
V = S * cos(z)
V = 9585
...
77 ft
∆elev = hi + V - rB = V = 1382
...
42+1382
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7 Equipment for Differential Leveling Telescopes
CIV 208: Week-4
The telescopes of leveling instruments define the line of
sight and magnify the view of a graduated rod against a
reference reticle, thereby enabling accurate readings to be
obtained
...
(Courtesy Leica Geosystems
AG
...
10 Automatic Levels
Objective Lens: This compound lens securely
mounted in the tubes object end, has its optical axis
reasonably concentric with the tube axis
...
Its function is to focus rays of light that pass through
the objective lens onto the reticle plane
...
Reticle: The reticle consists in a pair of perpendicular
reference lines (cross hairs) mounted at the principal
focus of the objective optical system
...
CIV 208: Week-4
31
CIV 208: Week-4
4
...
A sturdy tripod in good condition
is essential to obtain accurate results
...
The legs can
be made of wood, fiberglass, or metal
...
Which type of tripod would you like to
threw around by a leveling observation
...
14 Level Rods
CIV 208: Week-4
A variety of level rods are available
...
(a) Philadelphia rod (front)
...
(c)
Double-faced leveling rod with
metric graduations
...
CIV 208: Week-4
Week-2
4
...
• The need for some adjustments may be noticed during
use
...
• If the tests reveal conditions that should be adjusted,
depending on the particular instrument, and the
knowledge and experience of its operator, some or all of
the adjustments can be made immediately in the field
...
1 Introduction
This chapter concentrates on differential leveling, and
discuss handling the equipment, running and adjusting
simple leveling loops, and performing some project
surveys to obtain data for field and office use
...
2 Setting up a Level
Except for a few
instruments
that
employ a ball-andsocket arrangement, all
modern levels use a
three-screw
leveling
headfor initial rough
leveling
...
10
Tube-type level vial
...
11 Coincidence-type level vial correctly set in left view; twice the
deviation of the bubble shown in the right view
...
12
Bull’s-eye level vial
...
3 Duties of a Rod Person
The duties of a rod person are
relatively simple
...
A level rod must be held plumb on the
correct monument or turning point to
give the correct reading
...
42
CIV 208: Week-4
5
...
In running this circuit, the first reading, a plus sight, is
taken on the established benchmark BM
...
TPelev= HI – FS(-)
43
CIV 208: Week-4
44
CIV 208: Week-4
45
CIV 208: Week-4
Week-2
5
...
Formerly, it was used mainly for precise work, but it
can be used on prejects requiring only ordinary precision
...
(2) Producing greater accuracy because
average of three readings are available
(3) Furnishing stadia measurements of sight lenghts to asist
in balancing backsight and foresight distances
...
Distances has been obtained by
the stadia
48
CIV 208: Week-4
Week-2
5
...
Profile leveling which yields with elevations at
definite points along a reference line, provides the needed
data
...
9
...
The reference alignment will most often be the preoposed
construction centerline, although frequently offset
reference lines are used
...
50
CIV 208: Week-4
Week-2
5
...
2
...
The starting point is ususally designated
with some arbitrary value like 10+00
...
51
CIV 208: Week-4
52
CIV 208: Week-4
Week-2
5
...
3 Drawing and Using The Profile
Prior to drawing the profile, it is first necessary to compute
elevations along the reference line from the field notes
...
12 Sources of Errors In Leveling
1
...
Personal
• Line of sight:
* Bouble not centered
• Cross hair not exactly horizontal * Faulty rod readings
• Rod not correct lenght
* Parallax
• Tripod legs loose
* Rod handling
2
...
Distances can basicly be determined by multiplying the
parallax distance with 10
...
13 Mistakes
• Improper use of a long rod
• Holding the rod in different places for the plus and minus
sight on a turning point
• Reading a foot too high
• Waving a flat bottom rod while holding it on a flat surface
• Recording notes
• Touching tripod or instrument durind the reading
process
...
6: Distance Measurement
61