Contents
Ø Survey and
Leveling
Ø Object of
Survey
Ø Why should we
study Survey?
Ø Parts of
Surveyor work
Ø Shape of
Earth
Ø Primary
Division of Survey
Ø Classification
of survey
Ø Measurement
and Instruments
Ø Chain And
Tape
Ø Principle of
Survey
Ø Ranging Out
Survey Line
Ø Errors in
Length due to incorrect Chain
What is Serving
The process of determining by measurement, the relative positions of points above, on, or
beneath the earth surface, to produce map or
plan (which shows the feature of the
surface) in horizontal or vertical
plane.
Or
•
Surveying is the science of measuring and representing
natural and artificial features on the ground in a limited area, regarding the
earth as flat.
Leveling
•
The art of determining the relative heights or elevation of different points on the surface of the earth.
•
Determining the position of points in a vertical plane.
•
Surveying and leveling are considered as distinct operations, however, in a broad sense, the term surveying includes leveling.
Object OF Survey
•
The primary objective of the survey is the preparation of the plan and map of an area.
•
The result of the survey in the form of data when plotted and drawn on paper, we get a
plan/map.
•
If the scale is small it is called Plan.
E.g Plan of a Building let 1:100
•
If the scale is large, it is called Map.
E.g Map of Pakistan let 1:25,000
Why should we study surveying
•
You may be required to
perform simple surveying
operations (particularly if
you're employed in construction
company and Local Gov.), or you will
need to discuss your needs with surveyors.
•
Every Engineer needs
surveying skills
Parts of Surveyor’s work
•
Decision making (selecting techniques and equipment, etc.)
•
Fieldwork (data acquisition)
•
Data processing (calculations to give locations, areas, volumes, etc.)
•
Mapping (maps, plans, charts)
•
Reporting (conclusion of the task)
Shape of Earth
The earth is Approximately Spheroid
 |
|||
Primary Division of Survey
1. Geodetic Surveying
2. Plane surveying
2. Plane surveying
1. Geodetic or Trigonometrically Surveying:
•
When the radius of curvature of the earth is taken into
account.
•
Large area and large distances are covered.
•
The object of the geodetic survey is to determine precise
positions on the surface of the earth.
•
Refined Instruments and Methods are used.
•
Conducted by Government agencies.
Primary Division of Survey
•
Small area and small distances are covered
•
The degree of accuracy is comparatively low.
•
American survey put 250 km2 for treating
survey as Plane, but controlling factor
should be a degree of precision rather than the extent of the area.
Classification of Survey
1. Based upon
Nature of field
–
Land Survey
–
Marine Survey
–
Astronomical Survey
2. Based upon
Object of Survey
3. Based upon
Nature of field
–
Land Survey
–
Marine Survey
–
Astronomical Survey
Based upon Method Employed
–
Triangulation
–
Traversing
4. Based upon
Instrument Used
Chain, Theodolite, Compass, Plane
Table, Photographic and Aerial Surveys
•
Land Survey can be further divided into:
1.
Topographical Survey :
•
Determine the natural features of a country such as hills,
valleys, lakes woods, etc. and also arterial
features such as roads, buildings, canals, towns, etc.
2.
Cadastral Survey :
•
Details such bundles of houses, town, fields and other
properties pathways are determined.
-City Survey
-Engineering Survey
•
Engineering Survey can be further divided into:
Measurements & Instrumentation
What is measured?
•
Two kinds of measurements used in plane surveying.
•
In Surveying all measurements are horizontal, can be inclined, reduce to horizontal and
vertical components in plotting.
•
Distance between 2 points on a plan or map is always horizontal distance irrespective of
their elevation,(distance between their
projection on a horizontal plane).
•
Horizontal distance
•
Distance between two points in a horizontal plane
•
Vertical Distance
•
Distance between two points in a vertical plane
•
Horizontal angle
•
A horizontal angle is an angle formed in a horizontal plane by two intersecting horizontal lines.
•
Vertical angle
•
A Vertical angle is formed by two intersecting lines in a vertical plane, one of these
lines horizontal.
Measurements & Instrumentation
What is measured?
•
Distances
–To calculate areas, volumes, etc.
–To draw plans, maps, etc.
•
Angles
–Both horizontal and vertical
•
Heights
–Levels or elevations
How are these measured and which
the instrument should I use?
•
Distances (horizontal)
-Chaining, Taping (steel tape),
tachometer (theodolite), electronic
(EDM, GPS)
•
Angles
-tachometer (theodolite, total
station),
•
Heights
-leveling (level, theodolite, total
station)
Instruments For Measuring Distances
• Two main methods for measuring distances. (Linear Measurements)
A. Direct Method
• By chain or Tape or
other Instruments directly
• Distance is obtained by
calculation
eg:
Triangulation
Direct Measurement
Severe
All
methods/ Instruments are available
1.
Pacing
2.
Passometer
3.
Pedometer
4.
Odometer
5.
Speedometer
6.
Perambulator
7.
Judging
distance
8. Time Measurement
Chaining
•
Most Common method is
the method of measuring the distance with a
Chain or Tape, Called Chaining.
•
For Ordinary work
(less Precision) The chain is Used.
•
For Great Accuracy
Steel Tape is used.
•
Chaining
•
Taping
•
with Chain. with Tape.
•
The chain is composed of
100-150 pieces of galvanized mild steel
called LINKS.
Different
Types of Chain
• Following are the various types of chain in common use:
1)
Metric
chains
2) Steel band or Band chain
3)
Gunter`
s chain or surveyors chain
4) Engineers chain
5)
Revenue
chain)
Tapes
•
Tapes are made of
different materials
•
1) Cloth or linen
tape
-Used
for subsidiary measurements
-Very
light, easy to handle
-May
effect by moisture
•
2) Metric steel tape
-Made
of steel
-Outer
the end is provided with a ring for holding
•
3) Invar tape
-Used
for high precision work
-Made
of alloy steel
•
4) Synthetic tape
-Made
of glass fiber with PVC coating
-
These are used for short measurements
Principle of
Surveying
•
Two Fundamental
Principles
1.
To work from the Whole to the Part, not from the part to the Whole.
e.g.
set out the mainframe first, and add details onto the frame.
Object
of this system is to prevent the accumulation of errors and to control and localized minor errors.
2.
To Fix Position of New point (Station) by at
least two independent
processes.
New
The station can be fixed from points already fixed
By
1) Linear measurement 2) Angular measurement 3) or Both
Direct
Ranging
It
Is used while ranging on a plain ground,
when two points are indivisible.
PROCEDURE:
1.
»
Fix the ranging rods at the two given stations.
2.
»
The follower stand behind station A and directs the leader, with ranging rod to come in line with AB by
signals of ranging
3.
»
When the ranging rod comes in the line of AB the follower directs the leader to fix the ranging rod in position.
4.
»
Let the intermediate point be C which should be less than 100 feet.
•
Now the leader has taken another ranging rod
and stands between A and B about 2/3 distance
from A
» The follower directs the leader to come in
line of AB by using signals of ranging.
» As
and when the point is located in the line of AB the follower instructs to fix the ranging rod in position.
» Let the other intermediate position be D which
is less than 100 feet from B
» Now A, B, C, and D are in one line.
2. In
Direct Ranging
This
type of ranging is carried out when two sides are not indivisible.
Chaining
of a Line
•
Two men are required
•
1. Leader 2. Follower
•
Duties of Leader:
– To drag the chain
– To insert arrows at the end of survey chain length
– To obey instructions of the follower
– Duties of Follower:
– To place leader in line with ranging rod
– Always carry the rear handle in his hand
– To pick up the arrows inserted by the leaders.
Errors
in Length due to incorrect Chain
•
The most common errors
are that the chain may be too long or
too short.
•
It will be corrected by
using the formula
The length
of a line = L’/L * (Measured Distance)
•
If the chain is too long then
the measured length will be smaller than
the actual, so the error is negative and the correction is positive.
•
If the chain is too short
then the measured length will be too long that is longer than the actual, so the
error is positive and the correction is negative.
•
Prepared by Imad al
Abdallah
Thank you
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