Civil Engineering/Surveying/leveling/types of leveling /Profile levelling
Summary
TLDRThe script explains the process of profile leveling, a surveying technique used in engineering to determine the amount of earth to be cut or filled for leveled construction. It involves setting up a level instrument, taking readings at regular intervals along a central line, and recording these in a level notebook. The method includes marking points, taking foresights and backsights, and using either the height of instrument or rise and fall method for level reduction. The final step is plotting a profile, which graphically represents the ground points on a longitudinal section, with a larger vertical scale to highlight elevation differences.
Takeaways
- 📏 Profile leveling is a surveying technique used to determine earthwork quantities for construction projects.
- 📍 It is conducted along the central line of a track of land where linear engineering work is planned.
- 🔍 The process involves setting up a level instrument at various locations and taking readings at regular intervals.
- 📋 A benchmark is used as a reference point for taking back sights and foresights with a leveling staff.
- 📏 Turning points (TP) and salient points are marked and observed to capture changes in the gradient.
- 📊 The readings are recorded in a level notebook, detailing each observation's station and elevation.
- ✂️ The reduction of levels can be calculated using either the height of the instrument method or the rise and fall method.
- 📊 Plotting the profile leveling provides a graphical representation of the ground points on a longitudinal section.
- 📐 The vertical scale of the profile is typically larger than the horizontal scale to emphasize elevation differences.
- 📈 Segmented straight lines connecting the reduced level points represent the ground's longitudinal profile.
Q & A
What is profile leveling?
-Profile leveling is a method of surveying carried out along the central line of a track of land where a linear engineering work is to be constructed. It is also known as longitudinal sectioning.
Why is profile leveling important in engineering?
-Profile leveling is important as it helps determine how much earth needs to be cut or filled to make a leveled construction, which is essential for the planning and execution of linear engineering projects like roads, railways, and canals.
What are the steps involved in carrying out profile leveling?
-The steps include setting up the level on a convenient location, taking a backsight on a benchmark, marking points at regular intervals, taking observations at these points using a leveling staff, repositioning the instrument, and recording the readings in a level notebook.
How are the readings from profile leveling recorded?
-The readings are recorded in a level notebook with columns for backsight, intermediate sides, and foresight. The reduced levels of various stations are computed and plotted to create a profile.
What is the purpose of marking points at regular intervals during profile leveling?
-Marking points at regular intervals allows for systematic data collection along the alignment, which is necessary for accurately determining the depth of cutting or filling required at each point.
What is the significance of the benchmark in profile leveling?
-The benchmark serves as a reference point for the leveling process. A backsight is taken on this marked benchmark to establish a known starting elevation for the leveling work.
How are the reduced levels of various stations computed?
-The reduced levels can be computed using either the height of instrument method or the rise and fall method, which involve calculations based on the readings taken at different points along the profile.
What is the purpose of plotting a profile after leveling?
-Plotting a profile provides a graphical representation of the ground points on a longitudinal section, which helps visualize the elevation changes and plan the construction work more effectively.
Why is the vertical scale of a profile plot generally larger than the horizontal scale?
-The vertical scale is drawn larger than the horizontal scale to accentuate the differences in elevations, making it easier to identify and plan for the necessary earthwork.
How are salient points, such as changes in slope, recorded in profile leveling?
-Salient points like changes in slope are recorded by taking foresights at these points during the leveling process and noting down the readings in the level notebook.
Outlines
🏗️ Profile Leveling in Engineering Surveying
This paragraph introduces the concept of profile leveling, a surveying technique used by engineers to determine the amount of earth to be cut or filled for leveled construction. It explains that profile leveling is conducted along the central line of a track of land where linear engineering work is planned. The process involves marking the line on the ground, setting up a level at convenient locations, and taking observations at regular intervals using a leveling staff. The readings are recorded in a level notebook, and the reduction of levels can be done using either the height of the instrument method or the rise and fall method. The paragraph concludes with a brief mention of plotting a profile, which provides a graphical representation of the ground points on a longitudinal section.
📊 Plotting the Longitudinal Profile
The second paragraph delves into the plotting of profile leveling, which is essential for visually representing the ground points on a longitudinal section. It describes how to plot a profile by drawing a datum line and marking the distance of points, then plotting the reduced levels along vertical lines drawn on these marked points. The segmented straight lines joining the reduced levels represent the longitudinal profile of the ground surface. The paragraph mentions that the vertical scale of the profile is typically larger than the horizontal scale to emphasize the difference in elevations. The paragraph concludes with a reference to a figure that would show the complete profile of the longitudinal section of the profile leveling.
Mindmap
Keywords
💡Profile Leveling
💡Longitudinal Sectioning
💡Level Instrument
💡Benchmark
💡Back Sight
💡Foresight
💡Turning Point
💡Leveling Staff
💡Salient Point
💡Reduction of Levels
💡Plotting Profile
Highlights
Profile leveling is a surveying method used to determine the amount of earth to be cut or filled for leveled construction.
It is also known as longitudinal sectioning, used for linear engineering works like tracks or roads.
The process involves marking the central line of the land where the construction will take place.
A level instrument is set up at a convenient location to take observations.
Back sight is taken on a benchmark to establish a reference point.
Points are marked at regular intervals, such as every 10 meters, along the central line.
Observations are taken at these points using a leveling staff to measure the elevation.
The level instrument is repositioned to take further observations at different locations.
Readings are recorded in a level notebook, including back sights, foresights, and salient points.
The reduction of levels can be done using either the height of instrument method or the rise and fall method.
The reduced levels of various stations are computed and recorded.
Plotting of profile leveling provides a graphical representation of the ground points on a longitudinal section.
The vertical scale of the profile is typically larger than the horizontal scale to emphasize elevation differences.
A datum line is drawn for plotting, with distance of points marked along it.
Reduced levels are plotted along vertical lines drawn on marked points.
Segmented straight lines joining the reduced level points represent the longitudinal profile of the ground surface.
The final figure shows the complete profile of the longitudinal section of the profile leveling.
Transcripts
profile leveling
do you know how engineers come to decide
as to how much earth is to be cut or
filled to make a leveled construction
have you ever wondered how to determine
the depth of cutting
or filling on the proposed gradient
well it is determined by plotting a
profile leveling
and now we will learn in detail how it
is done
profile leveling is a method of
surveying
that has been carried out along the
central line
of a track of land on which a linear
engineering work is to be constructed
profile
leveling is also known as longitudinal
sectioning the line along which a
profile runs
is to be marked on the ground before
taking
any observation to carry out profile
leveling
firstly set up the level on a convenient
location
say l1 level the instrument
and take a back sight on a marked
as the benchmark now
mark points at regular intervals say 10
meters
on the lineup to the turning point dp1
take the observations at these regular
intervals
using leveling staff take a foresight on
turning point tp1
and note down all the readings now let
us
reposition the instrument to some other
convenient
location l2 set up the instrument
and level it on the location l2
now take a backsight on tp1 and take
readings at regular intervals using a
leveling staff
now take a foresight on the final
station c
and also take the readings at salient
point
say x where changes in slope occur
as soon as readings are taken the notes
of the profile
are recorded in a level notebook
the readings are filled in the notebook
as
follows for instrument position at
l1 the back side is taken at benchmark
and the reading of 3.005
meters is placed in its column in the
row of station a
the readings for intermediate sides for
one is 2.285 meters
2 is 1.56 meters
3 is 1.785 meters
and for 4 is 2.105
meters are placed in the corresponding
row
the foresight taken at the station tp1
3.105 meters is placed
in its row after changing the instrument
location
the back side at tp1 is entered in its
row
in the back side column the readings
intermediate sides for 5 is 3.465 meters
6 is 3.12 meters
7 is 3.015 meters
8 is 2.58 meters
and 9 is 1.955 meters
are placed in the corresponding row
the readings of the salient point x
is 3.955 meters
is placed between the intermediate sides
at its place
the foresight 1.465 meters
taken at station c is placed in its row
the reduction of levels can be done
either
by height of instrument method or rise
and fall method
the following table indicates the
computations done by both
height of the instrument and rise and
fall methods
now that the reduced levels of various
stations are known
let us learn how to plot a profile
plotting of profile leveling provides a
graphical representation
of the ground points on a longitudinal
section
along the alignment the vertical scale
of the profile is
generally drawn much larger than the
horizontal scale
in order to accentuate the difference of
elevations
to plot a profile a datum line is drawn
along which distance of points are
marked
the reduced levels are plotted along
vertical
lines drawn on marked points
segmented straight lines joining the
reduced
level points represent the longitudinal
profile
of the ground surface the following
figure
shows the complete profile of
longitudinal section
of the profile leveling
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