Leveling
Florence A. Galeon
Assistant Professor
U.P. College of Engineering
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Outline
I.
II.
III.
IV.
Introduction
Definition of Leveling Terms
Methods of Measuring Differences in Elevation
Common Instruments and Accessories
Used in Leveling
V. Differential Leveling
VI. Sample Problem
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Leveling
It is the process of finding the difference in
elevation between two points by measuring
the vertical distance between the level
surfaces through the points.
It is a relatively simple process but an
important one in all construction work, in
setting machinery and equipment, and in
the fabrication of large objects such as
ships and airplanes.
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Definition of leveling terms
Level Surface – is a curved surface every
element at which is normal to the plumbline.
Level Line – is a curved line in a level
surface all parts of which is equidistant from
the center of mass of the earth.
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Definition of leveling terms
Vertical Line – is a line in the direction of a
plumb line.
Horizontal Line – is a straight line tangent to
a level line. It is perpendicular to the vertical
or plumb line through the point of tangency.
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Definition of leveling terms
Elevation – is a vertical distance above or
below some arbitrarily assumed level
surface or datum.
Mean Sea Level – is the surface of the sea
exactly midway between high and low tides
and is regarded as the reference surface to
which all elevations are referred.
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Definition of leveling terms
Datum – is a surface of reference
coincident or parallel with mean sea level to
which all elevations of a given region are
referred.
Difference in Elevation – is the vertical
distance between an imaginary level
surface containing the high point and a
similar surface containing the low point.
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Methods of Measuring Differences in
Elevation
1.
Direct (Spirit) Leveling
It is the operation of determining the
elevation of points some distance apart by a
series of set-ups of a leveling instrument
along a designated route.
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Direct Leveling Set-up
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Methods of Measuring Differences in Elevation
2.
Reciprocal Leveling
It is the process of determining accurately
the relative elevations of two intervisible
points a considerable distance apart between
which points levels cannot be run in the
ordinary manner of leveling.
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Reciprocal Leveling Set-up
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Methods of Measuring Differences in Elevation
3.
Profile Leveling
It is the operation of determining the
differences in elevation between points at
designated short measured intervals along an
established line to provide data from which a
vertical section of the ground surface along a
surveyed line can be plotted.
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Sample Land Profile
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Sample Land Profiles
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Sample Land Profile
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Methods of Measuring Differences in Elevation
4.
Barometric Leveling
It is an operation of determining
differences in elevation by observing the
atmospheric pressure at different stations by
means of a barometer.
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Different Types of Barometers
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Different Types of Barometers
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Methods of Measuring Differences in Elevation
5.
Trigonometric Leveling
It is a method of determining the difference in
elevation between two points by measuring the
horizontal or inclined distance between the points and
determining the angle between a horizontal line and the
inclined line that joins the points.
h
α
d
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Methods of Measuring Differences in Elevation
6.
Borrow-Pit Leveling
It is the process of determining the
relative elevations of points in borrow-pit
excavations for the purpose of calculating
volumes of earthwork.
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Natural Borrow-Pit & Profile
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Common Instruments and Accessories
Used in Leveling
Engineer’s Level
Tilting Level
Automatic Level
Hand Level
Digital Level
Leveling Rods
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Engineer’s & Tilting Levels
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Automatic Levels
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Hand Levels
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Digital Levels
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Leveling Rods
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Level & Rod
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Differential Leveling
n
Definition:
n
It is the process of determining the
difference in elevation between two
points in which a line of level is run
from BM₁ to BM₂.
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Differential Leveling Illustration
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Differential Leveling Terms
Bench Mark (BM) – is a definite point on
an object the elevation of which is
known.
Backsight (BS) – is a rod reading taken
on a point of known elevation.
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Differential Leveling Terms
Foresight (FS) - is a rod reading taken on
a point the elevation of which is to
be determined.
Backsight Distance (BSD) – is the
horizontal distance from the
center of the instrument to the rod
on which a backsight is taken.
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Differential Leveling Terms
Foresight Distance (FSD) - is the
horizontal distance from the
center of the instrument to the rod
on which a foresight is taken.
Turning Point (TP) – is an intervening
point between two bench marks
upon which point foresight and
backsight rod readings are taken.
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Differential Leveling Terms
Height of Instrument (HI) – is the
elevation of the line of sight of the
telescope when the instrument is
leveled.
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S
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