Yabancı Dil III (YDL285)
Leveling
Yrd. Doç. Dr. Saygın ABDİKAN
2016-2017 Öğretim Yılı Güz Dönemi
1
Cadastral surveying

Cadastral surveying is a
branch of the surveying
profession that is
concerned with land
management, and more
specifically
 with issues of land
ownership, measurement
and delineation of property
boundaries.
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Boundary surveying

A survey that establishes or
re-establishes boundaries of
a parcel using a legal
description
 It involves the setting or
restoration of monuments
(sınır taşı) or markers at the
corners or along the lines of
the parcel.
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4
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Topography is a combination of methods and
instruments to comprehensively measure and
represent details of the Earth’s surface:

planimetry: to determine the relative positions of the
representation of points on the Earth’s surface with
respect to the same reference surface;
 altimetry: to determine the height of the points on the
Earth’s surface with respect to the geoid surface;
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
Geoid: is a model of global mean sea
level that is used to measure precise
surface elevations.

The geoid is the shape that the surface
of the oceans would take under the
influence of Earth’s gravity and rotation
alone, in the absence of other influences
such as winds and tides.
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tachymetry: for the planimetric and
altimetric survey of the Earth’s surface
zones;
 land surveying: to measure areas,
moving and rectify borders, levelling
zones of the Earth physical surface.

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Topographic Surveys are used to identify
and map;
 the contours of the ground and
 existing features on the surface of the
earth or slightly above or below the
earth's surface (i.e. trees, buildings,
streets, walkways, manholes, utility
poles, retaining walls, etc.).
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
Topographic
maps show
elevation of
landforms above
sea level;
 Bathymetric maps
show depths of
landforms below
sea level.
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The most common method of representing
the topography of an area is to use contour
lines yükseklik eğrisi/eşyükseklik eğrisi/münhani
A contour line is an imaginary level line
that connects points of equal elevation
11
http://www.ce.memphis.edu/1101/notes/surveying

Contours that point up
hill can indicate a
valley or stream

Contours show the
steepest part of this
terrain and the
shallowest part of the
topography
12
http://www.ce.memphis.edu/1101/notes/surveying
Characteristics of Contours

The contour interval should be small enough to give the
desired topographic detail
 Usually every fifth contour line is shown in a heavy,
wider line, this is called a index line/principal contour
 Closely spaced contours indicate steep slopes
 Widely spaced contours indicate moderate slopes
 Contours should be labeled to the elevation value
 Contour line do not cross
 Important points can be further defined by including a
“spot” elevation
 Contour lines tend to parallel each other on uniform
slopes
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INTRODUCTION TO LEVELING
Areas of Application:
• design of highways, railroads, canals, etc.
• Layout construction projects according to specific
design
•
•
•
•
calculate earthwork volumes
investigate drainage characteristics
map earth’s topography
monitor earth subsidence
Types of Level

Builder's/Engineer's Level: As implied by
the name, these are used by builders
and engineers. The accuracy of a single
reading will be about 2-3mm.
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
Digital Level: This type of level uses a special
bar-coded staff. The image of the staff passes
through the objective lens and then via a beam
splitter to a photodetector array, where it is
digitized.
 The microprocessor compares this image to a
copy of the bar code and calculates the staff
reading, which is displayed and/or stored. The
sensitivity of the device is such that single
reading accuracies of 0.2mm to 0.3mm can be
achieved, and sight lengths can be extended
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up to 100m.

Precise Level: This is a modification of
the conventional level in which a parallel
plate micrometer is placed in front of the
objective lens. This allows the image of
the staff graduation to be moved up or
down by very small measurable
amounts. For sight lengths of under 50m,
single reading accuracies of 0.02mm to
0.03mm can be achieved.
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Dumpy Level


A dumpy level, builder's auto level, leveling
instrument, or automatic level is an optical
instrument used to establish or check points in the
same horizontal plane.
It is used in surveying and building to transfer,
measure, or set horizontal levels.
DEFINITIONS
1. Level Surface:
A curved surface that at every point is perpendicular to the direction of gravity (plumbline), e.g.
still lake surface
2. Datum:
A level surface to which elevations are referred (i.e. reference surface such as MSL)
3. Mean Sea Level (MSL):
Average elevation of the sea surface measured over a period of 19 years
4. Bench Mark (BM):
A permanent reference point with a known elevation (relative to some datum, usually MSL)
5. Leveling:
The process of measuring elevation differences between different points
6. Vertical Control:
A series of points of known elevation established throughout an area
A
B
VERTICAL ANGLE - Angle between line AB and horizontal line
HORIZONTAL LINE - Line perpendicular to the vertical
ELEVATION - Vertical distance (height difference) between datum and point
Levelling
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LEVELING METHODS





Differential Leveling (Geometric leveling)
Trigonometric Leveling
Barometric Leveling
Hydrostatic Leveling
GPS Leveling
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LEVELING METHODS
1. Differential Leveling (Geometric leveling)
Backsight (BS)
FS
1.20
Geri okuma
TP1
8.42
Level set up half way between BM A and TP1 - equal BS and FS
BM A
(820.00)
DhAB = BS - FS = 8.42 - 1.20 = 7.22
hB
= 820.00 + DhAB
Bench mark (BM) - relatively permanent point of known elevation
• Backsight (BS) - a sight taken to the level rod held at a point of
known elevation
• Foresight (FS) - a sight taken on any point to determine its
elevation
• The backsight reading is added to the elevation of the known point
to compute the height of the instrument (HI)
• The level may be moved to a temporary point called a turning point
(TP)
• The elevation of a point is the height of the instrument (HI) minus
the foresight (FS)
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Common Mistakes
• Level rod not vertical
• Settling of leveling rod
• Leveling rod not fully
extended or incorrect length
• Level instrument not level
• Instrument out of
adjustment
• Environment - wind and
heat
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LEVELING METHODS
D
TRIGONOMETRIC LEVELING
r
Measurement of vertical angle wıth teodolit
V
S
B
z
C
a
hi
H
A
DZCD = V = S Sin a = S Cos z
= H Cot z
DZAB = hi + V - r
OR ZB = ZA + hi + S Sin a - r
= ZA + hi + H Cot z - r
LEVELING METHODS
BAROMETRIC LEVELING
•
Barometer measures air pressure which is directly related to elevation
•
Changes in pressure due to temperature changes, changes in weather
conditions, etc can be taken into account by leaving one barometer on
a control point (e.g. BM)
•
Accuracies of 2-3 ft (0.6 - 1 meter) are possible
LEVELING METHODS
GPS Leveling
Differential Leveling gives ORTHOMETRIC HEIGHTS
(above Mean Sea Level)
GPS gives ELLIPSOIDAL HEIGHTS (above ellipsoid)
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http://www.esri.com/news/arcuser/0703/geoid1of3.html
Mean Sea Level

For generations, the only way to express topographic or
bathymetric elevation was to relate it to sea level.
 Geodesists once believed that the sea was in balance
with the earth’s gravity and formed a perfectly regular
figure.
 MSL is usually described as a tidal datum that is the
arithmetic mean of hourly water elevations observed
over a specific 29 year cycle.
 MSL is defined as the zero elevation for a local area.
The zero surface referenced by elevation is called a
vertical datum.
30
http://www.esri.com/news/arcuser/0703/geoid1of3.html
BASIC PARTS OF A LEVEL
Gözlem çizgileri plakası
eyepiece
Oküler
reticle
telescope
objective lens
line of sight Gözlem çizgileri
plakası
level bubble
Küresel düzeç
leveling screws
Ayar vidaları
tripod
Üç ayak sehpa
Older instruments – Dumpy, Wye
 Automatic level (compensator)
 Laser
 Digital

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Compensating Prism in Automatic Level
compensator
Automatic compensator orients line of sight in a horizontal plane

Due to the curvature of the Earth, the line of
sight at the instrument will deviate from a
horizontal line as one moves away from the
level:
Earth Curvature
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Refraction:

The variable density of the Earth's atmosphere
causes a bending of the ray from the staff to
the level.
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LEVELING FIELD PROCEDURE
Setting up Level:
 balance BS and FS
 Make sure rod will be visible when instrument leveled
at new position
Rod Person:
 hold rod vertical (plumb)
 move rod back and forth (minimum reading noted)
 select TP’s that are stable
Differential Leveling Procedure:
 start with BS on starting BM
 take FS and BS on all intermediate points (TP’s)
 close with FS on ending BM