Civil engineering land surveying basics pdf

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Assala mu alykum My Name is saqib imran and I am the
student of b.tech (civil) in sarhad univeristy of
science and technology peshawer.
I have written this notes by different websites and
some by self and prepare it for the student and also
for engineer who work on field to get some knowledge
from it.
I hope you all students may like it.
Remember me in your pray, allah bless me and all of
you friends.
If u have any confusion in this notes contact me on my
gmail id: Saqibimran43@gmail.com
or text me on 0341-7549889.
Saqib imran.

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Surveying
Surveying is the art of determining the relative positions of different objects on the surface of
the earth by measuring the horizontal distances between them, and by preparing a map to any
suitable scale. Thus, in discipline, the measurements are taken only in the horizontal plane.
Contents:
 Object
 Uses
 Principles
Object of surveying
The aim of surveying is to prepare a map to show the relative positions of the objects on the
surface of the earth. The map is drawn to some suitable scale. It shows the natural features of
a country, such as towns, villages, roads, railways, rivers, etc. Maps also include details of
different engineering works, such as roads, railways, irrigation canals, etc.
Uses of surveying
Surveying may be used for the following various applications:
1. To prepare a topographical map which shows the hills, valleys, rivers, villages, towns,
forests, etc. of a country.
2. To prepare a cadastral map showing the boundaries of fields, houses and other
properties.

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3. To prepare an engineering map which shows the details of engineering works such as
roads, railways, reservoirs, irrigation canals, etc.
4. To prepare a military map showing the road and railway communications with different
parts of a country. Such a map also shows the different strategic points important for
the defence of a country.
5. To prepare a contour map to determine the capacity of a reservoir and to find the best
possible route for roads, railways, etc.
6. To prepare a geological map showing areas including underground resources.
7. To prepare an archaeological map including places where ancient relics exist.
General Principles of surveying
The general principles of surveying are:
1. To work from the whole to the part
2. To locate a new station by at least two measurements (linear or angular) from fixed
reference points.
According to the first principle, the whole area is first enclosed by main stations (i.e.
Controlling stations) and main survey lines (i.e. controlling lines). The area is then divided
into a number of parts by forming well conditioned triangles. A nearly equilateral triangle is
considered to be the best well-conditioned triangle.The main survey lines are measured very
accurately with a standard chain. Then the sides of the triangles are measured. The purpose of
this process of working is to prevent accumulation of error. During the procedure, if there is
any error in the measurement of any side of a triangle, then it will not affect the whole work.
The error can always be detected and eliminated.
According to the second principle, the new stations should always be fixed by at least two
measurements (linear or angular) from fixed reference points. Linear measurements refer to
horizontal distances measured by chain or tape. Angular measurements refer to the magnetic
bearing or horizontal angle taken by a prismatic compass or theodolite.
In chain surveying, the positions of main stations and directions of main survey lines are fixed
by tie lines and check lines.
Types of Surveying

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Surveying is primarily classified as under:
1. Plane surveying
2. Geodetic Surveying
Plane Surveying is that type of surveying in which the mean surface of the earth is
considered as a plane and the spheroidal shape is neglected. All triangles formed by survey
lines are considered plane triangles. The level line is considered straight and all plumb lines
are considered parallel. In everyday life were are concerned with small portion of earth’s
surface and the above assumptions seems to be reasonable in light of the fact that the length of
an arc 12 kilometers long lying in the earth’s surface is only 1cm greater than the subtended
chord and further that the difference between the sum of the angles in a plane triangle and the
sum of those in a spherical triangle is only one second for a triangle at the earth’s surface
having an area of 195 sq. km.
Geodetic Surveying is that type of surveying in which the shape of the earth is taken into
account. All lines lying in the surface are curved lines and the triangles are spherical triangles.
It therefore, involves spherical trigonometry. All Geodetic surveys include work of larger
magnitude and high degree of precision. The object of geodetic survey is to determine the
precise position on the surface of the earth, of a system of widely distant points which form
control stations to which surveys of less precision may be referred.
Classification of surveying
Surveys may be secondarily classified under no. of headings which define the uses or purpose
of resulting maps.

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Classification based upon nature of field:
There are three types of surveying based upon the nature of field which are as follows:
1. Land Surveying: It can be further classified as i) Topographical survey ii) Cadastrial
Survey and iii) City Survey. It generally deals with natural or artificial features on land
such as rivers, streams, lakes, wood, hills, roads, railways, canals, towns, water supply
systems, buildings & properties etc.
2. Marine Surveying: Marine or hydrographic survey deals with bodies of water for
purpose of navigation, water supply, harbour works or for determination of mean sea
level. The work consists in measurement of discharge of streams, making topographic
survey of shores and banks, taking and locating soundings to determine the depth of
water and observing the fluctutations of the ocean tide.
3. Astronomical Surveying: The astronomical survey offers the surveyor means of
determining the absolute location of any point or the absolute location of and direction
of any line on the surface of the earth. This consists in observations to the heavenly
bodies such as the sun or any fixed star.
Classification based on object:
Based on object, there are four types of surveying which are as follows:
1. Geological Surveying
2. Mine Surveying
3. Archaeological surveying
4. Military surveying
Classification based on instruments used:
Based on various types of instruments used, surveying can be classified into six types.
1. Chain surveying
2. Compass surveying
3. Plane table surveying
4. Theodolite surveying
5. Tacheometric surveying
6. Photographic surveying
Classification based on methods used:
Based on methods adopted, surveying can be categorized into:
1. Triangulation surveying
2. Traverse surveying

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Levelling
Levelling (or Leveling) is a branch of surveying, the object of which is: i) to find the elevations
of given points with respect to a given or assumed datum, and ii) to establish points at a given
or assumed datum. The first operation is required to enable the works to be designed while the
second operation is required in the setting out of all kinds of engineering works. Levelling
deals with measurements in a vertical plane.
Level surface: A level surface is defined as a curved surface which at each point is
perpendicular to the direction of gravity at the point. The surface of a still water is a truly level
surface. Any surface parallel to the mean spheroidal surface of the earth is, therefore, a level
surface.
Level line: A level line is a line lying in a level surface. It is, therefore, normal to the plumb
line at all points.
Horizontal plane: Horizontal plane through a point is a plane tangential to the level surface
at that point. It is, therefore, perpendicular to the plumb line through the point.
Horizontal line: It is a straight line tangential to the level line at a point. It is also perpendicular
to the plumb line.
Vertical line: It is a line normal to the level line at a point. It is commonly considered to be
the line defined by a plumb line.
Datum: Datum is any surface to which elevation are referred. The mean sea level affords a
convenient datum world over, and elevations are commonly given as so much above or below
sea level. It is often more convenient, however, to assume some other datum, specially, if only
the relative elevation of points are required.

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Elevation: The elevation of a point on or near the surface of the earth is its vertical distance
above or below an arbitrarily assumed level surface or datum. The difference in elevation
between two points is the vertical distance between the two level surface in which the two
points lie.
Vertical angle: Vertical angle is an angle between two intersecting lines in a vertical plane.
Generally, one of these lines is horizontal.
Mean sea level: It is the average height of the sea for all stages of the tides. At any particular
place it is derived by averaging the hourly tide heights over a long period of 19 years.
Bench Mark: It is a relatively permanent point of reference whose elevation with respect to
some assumed datum is known. It is used either as a starting point for levelling or as a point
upon which to close as a check.
Methods of levelling
Three principle methods are used for determining differences in elevation, namely, barometric
levelling, trigonometric levelling and spirit levelling.
Barometric levelling
Barometric levelling makes use of the phenomenon that difference in elevation between two
points is proportional to the difference in atmospheric pressures at these points. A barometer,
therefore, may be used and the readings observed at different points would yield a measure of
the relative elevation of those points.
At a given point, the atmospheric pressure doesn’t remain constant in the course of the day,
even in the course of an hour. The method is, therefore, relatively inaccurate and is little used
in surveying work except on reconnaissance or exploratory survey.
Trigonometric Levelling (Indirect Levelling)
Trigonometric or Indirect levelling is the process of levelling in which the elevations of points
are computed from the vertical angles and horizontal distances measured in the field, just as
the length of any side in any triangle can be computed from proper trigonometric relations. In
a modified form called stadia levelling, commonly used in mapping, both the difference in
elevation and the horizontal distance between the points are directly computed from the
measured vertical angles and staff readings.
Spirit Levelling (Direct Levelling)
It is that branch of levelling in which the vertical distances with respect to a horizontal line
(perpendicular to the direction of gravity) may be used to determine the relative difference in

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elevation between two adjacent points. A horizontal plane of sight tangent to level surface at
any point is readily established by means of a spirit level or a level vial. In spirit levelling, a
spirit level and a sighting device (telescope) are combined and vertical distances are measured
by observing on graduated rods placed on the points. The method is also known as direct
levelling. It is the most precise method of determining elevations and the one most commonly
used by engineers.
Levelling Instruments
The instruments commonly used in direct levelling are:
1. A level
2. A levelling staff
Dumpy Level
The dumpy level originally designed by Gravatt, consists of a telescope tube firmly secured in
two collars fixed by adjusting screws to the stage carried by the vertical spindle. The modern
form of dumpy level has the telescope tube and the vertical spindle cast in one piece and a long
bubble tube is attached to the top of the telescope. This form is known as solid dumpy.
Components of Dumpy Level
The name “dumpy level” originated from the fact that formerly this level was equipped with
an inverting eye-piece and hence was shorter than Wye level of the same magnifying power.
However, modern forms of dumpy level generally have erecting eye-piece so that inverted
image of the staff is visible in the field of view. In some of the instruments, a clamp screw is
provided to control the movements of the spindle about the vertical axis. For small or precise
movement, a slow motion screw ( or tangent screw) is also provided. Some of the important
parts of Dumpy Level are listed and described below:

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1. Tripod Stand: The tripod consists of three legs which may be solid or framed. The
legs are made of light and hard wood. The lower ends of the legs are fitted with steel
shoes.
2. Levelling head: The levelling head consists of two parallel triangular plates having
three grooves to support the foot screws.
3. Foot screws: Three foot screws are provided between the trivet and tribrach. By turning
the foot screws the tribrach can be raised or lowered to bring the bubble to the center
of its run.
4. Telescope: The telescope consists of two metal tubes, one moving within the other. It
also consists of an object glass and an eye-piece on opposite ends. A diaphragm is fixed
with the telescope just in front of the eye-piece. The diaphragm carries cross-hairs. The
telescope is focused by means of the focusing screw and may have either external
focusing, or internal focusing.
In the external focusing telescope, the diaphragm is fixed to the outer tube and the
objective to the inner tube. By turning the focusing screw the distance between the
objective and diaphragm is altered to form a real image or the plane of cross hairs.
In the internal focusing telescope, the objective and eye-piece do not move when the
focusing screw is turned. Here, a double concave lens is fitted with rack and pinion
arrangement between the eye-piece and the objective. This lens moves to and fro when
the focusing screw is turned and a real image is formed on the plane of cross-hairs.
5. Bubble tubes: Two bubble tubes, one called the longitudinal bubble tube and other
the cross bubble tube, are placed at right angles to each other. These tubes contain spirit

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bubble. The bubble is brought to the center with the help of foot screws. The bubble
tube are fixed on top of the telescope.
6. Compass: A compass is provided just below the telescope for taking the magnetic
bearing of a line when required.
The compass is graduated in such a way that a ‘pointer’, which is fixed to the body of
compass, indicates a reading of 0 degree when the telescope is directed along the north
line.In some compasses, the pointer shows a reading of a few degrees when the
telescope is directed towards the north. This reading should be taken as the initial
reading. The bearing is obtained by deducting the initial reading from the final reading
of the compass.
Advantages of Dumpy Level
The advantages of dumpy level over the Wye Level are:
1. Simpler construction with fewer movable parts.
2. Fewer adjustments to be made.
3. Longer life of the adjustments.
Surveying and Levelling
What is Surveying and Levelling?
Surveying is an art of making measurements on as will determine the relative position of
different points on the surface of the earth.
It is essentially a process of finding position of different points
on the horizontal plane.
Levelling is the art of determining and representing the relative heights or elevations of
different points on the surface of earth.
Surveying deals with the position of points in the horizontal plane whereas Levelling
includes relative position of points in a vertical plane.
Although Surveying and Levelling are two different distinct operations.
Whereas if we see in the broader sense Then the term Surveying also includes
Levelling.
Plan and a Map | Basic difference between Plan and
Map

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The main Object of the survey is to develop a plan and a map.
The results of surveys when drawn on a paper forms a plan or a map.
On a plan or a map only horizontal distances are shown.
The plan or map is made according to some scale chosen.
If the scale is small ,the representation is called map, while it is called plan
if the scale is large.
We can understand this by considering that the map of a country is made to a very small
scale.
So that information represented should not exceed to the paper.
While the plan of the building is made large and large scale is chosen for that.
Therefore the basic difference between plan and a map is that of scale.
Only horizontal distances are shown on a plan or a map.
Vertical distances are correctly shown by means of vertical sections called sections.
Geodetic Surveying | Trigonometrical Surveying
When the survey conducted by considering the earth’s surface spheroidal, or by
considering the curvature of earth.Then this type of survey is known as Geodetic
Surveying.
Since we consider earth to be spheroidal so the line joining any two points on the surface
of the earth must be curve or is an arc of great circle.
It is also known as trigonometrical surveying. This type of survey is conducted where
Large distances and areas are to be surveyed.
Characteristics of Geodetic Surveying :
Following are the characteristics of Geodetic Survey.
 Very refined instruments are used in this survey.
 High precision is achieved through this.
 Very refined methods of observation and adjustment are used.
Definition of Plane survey :

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The type of survey in which curvature of earth is not taken into account,as the
survey is extend over small areas, is known as the plane Survey.
 This is called plane survey because the Earth’s surface is considered to be Plane
in this kind of Survey.
 The line connecting any two points will be the straight line and the angles thus
formed are also plane angles.
 It therefore involves knowledge of Geometry and plane trigonometry.
 The accuracy required for this type of survey is comparatively low as compare to
Geodetic surveying.
 American Surveyors put the limit of 250 sq km for treating Survey as a plane
survey.
 However degree of precision is also very important.
 If high precision is required then the survey should be Geodetic otherwise for low
precision we can prefer plane survey.
Topographical Survey
“The type of Land survey in which we determine the natural features of a country such
as hills, valleys, rivers, nallas, lakes, woods, etc.
and also determine the artificial features such as roads, railways, canals, buildings,
towns, villages, etc., is known as Topographical Survey.”
From Artificial features we mean the structures made by man or man made structures
which are not exist in nature
but made by man using resources found in nature.
Cadastral Survey
The type of Land Survey in which further details such as boundaries of houses, fields and
other properties are determined in known as cadastral survey.
This type of Survey includes additional details.
Engineering Survey | Reconnaissance Survey |
Preliminary Survey | Location Survey

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The survey which is conducted for determining quantities and for collecting data for the
designing of engineering works such as roads, railways, etc., is known as Engineering
Survey.
Engineering survey have following types:
Reconnaissance Survey
The Survey which is done for the feasibility* and rough cost of the project
is known as Reconnaissance Survey.
Preliminary Survey
The survey in which more precise information is required for the choice of best location
for the project and to estimate the exact quantities and costs of project is known as
PreliminarySurvey.
Location Survey
The survey for setting out the work on the ground is known as location survey.
Reconnaissance means military observation of an area to gain information.
Feasibility means either the project will complete or not.
Control Points | Reference Points
The points which are used as a reference to conduct other kind of Survey are known as
Control points.
These points are formed by triangulation or precise traversing.
High precision is required to form control points as other surveys are being conducted
with reference to these control points.
Triangulation
Triangulation is the process in which the area to be surveyed are divided into large
triangles, which are surveyed with great accuracy.These triangles are further sub
divided into small triangles
which are surveyed with less accuracy.
This process is done to prevent the accumulation of error and to control or minimize minor
errors.
What are Cumulative Errors ?
The errors which are accumulate at the end of the survey are known as Cumulative
errors. These type of errors occur when we contradict the main principle of Survey
which is

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To work from whole to part.
When we work from part to whole* than errors are magnified in the end and the process
becomes
uncontrollable at the end.
Part to whole means that first we surveyed small triangles and then expand these small
triangles
into large triangles covering the area.
The error in survey in the small triangles will be magnified when we expand it to large
triangle.
What is a Scale ?
Scale of a map or a drawing is actually the proportion between the distance on the map
or drawing to the corresponding distance on the ground.Thus if on a map it is written 1
cm = 10 m It means that 1 cm on the drawing is actually 10 m on the ground.
What is Pacing?
The method of measuring distance with the help of pace length is known as pacing.
This type of method is used where approximate results are required.
The length of the pace (generally vary from person to person) is multiplied by the
number of paces to measure the total distance.
Passometer | Pedometer
Passometer is a pocket instrument which count the number of paces. It automatically
records the number of paces. Its mechanism is being operated by the motion of the body.It
should be held vertically in pocket.
Pedometer The device which measured the distance automatically is known as
pedometer. It is similar to passometer but difference is that passometer count the number
of paces whereas pedometer records the distance.It is adjusted according to the length
of the pace of the person carrying it.
Odometer | Perambulator
Odometer
The device which attached with the wheel of any vehicle and records the number of
revolutions of the wheel is known as odometer.
The number of revolutions multiplied by the circumference of the wheel and records the

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distance.
Perambulator
The instrument provided with single wheel with forks and handle to measure the
distance between
two points is known as perambulator.
The instrument is wheeled along the line the length of which is desired.The distance
traverse
is automatically registered on the dials.
Chaining and Taping
The measurement of distance with the help of chain or tape is known as chaining.
However the term chaining should be used for the distance measured with the help of
chain,
the term taping should be used when measuring distance with the help of tape.
However the term chaining is still used for measuring distance either by tape or chain.
Ranging | Direct Ranging | Indirect Ranging
The process of establishing or developing intermediate points between two terminal
points or end points on a straight line is known as ranging.
Ranging is of two types
Direct Ranging
The ranging in which intermediate ranging rods are placed in a straight line by direct
observation from either end.
Direct ranging is possible only when the end stations are inter visible.
Indirect Ranging
The ranging in which intermediate points are interpolated by reciprocal ranging or
running an auxiliary line.
Indirect ranging is done where end points are not visible and the ground is high .
Survey Stations | Main Stations | Subsidiary or Tie
Station
A Survey Station is a point of Importance at the beginning and end of a chain line. There
are two main types of stations namely Main station and Subsidiary or Tie station.

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Main stations are the ends of the lines which command the Boundary of the survey,
and the lines joining the main stations are called main Survey or Chain lines.
Subsidiary or tie station
Any Point selected on the main survey line where it is necessary to run the auxiliary
lines to locate the interior details such as fences, hedges, buildings,etc., when they are
at some distance from the main survey lines are known as Subsidiary or Tie stations .
The lines joining such stations are known as tie line or subsidiary line.
Base Line
This term is often used in Chain Surveying, The longest of the chain lines formed in
doing a survey is generally regarded as the base line.
It is the most important line in doing survey .
The framework of the whole survey built up on the base line as it fixes up the direction
of all other lines.It should be measured with great accuracy and precision .For accuracy
The base line should be measured twice or thrice.
Hooke’s Law of Elasticity | Definition of Elastic
Materials
Hooke’s law of elasticity:
In mechanics, and physics, Hooke’s law of elasticity is an approximation that states that
the amount by which a material body is deformed (the strain) is linearly related to the
force causing the deformation (the stress).
Behavior is linear, If shown on a graph, the line should show a direct
variation.
Mathematical Form of Hookes Law:
For systems that obey Hooke’s law, the extension produced is directly proportional to
the load:
F=-kX Where
X=is the distance that the spring has been stretched or compressed away from the
equilibrium position.
F=is the restoring force exerted by the material (usually in newtons), and
K=is the force constant (or spring constant). The constant has units of force per unit
length (usually in newton per meter).
Elastic Materials:

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Objects that quickly regain their original shape after being deformed by a force, with the
molecules or atoms of their material returning to the initial state of stable equilibrium,
often obey Hooke’s law.
Hydrologic Cycle | Various Aspects of Hydrologic
Cycle | Engineering applications
Hydrologic Cycle:
The various aspects of water related to earth and their interaction can be explained in
terms of a cycleknown as hydrologic cycle.
Evaporation of water from the water bodies such as oceans and lakes,
evapotranspiration, formation and movement of clouds, precipitation in the form of rainfall,
snowfall, etc. surface runoff, stream flow and ground water movement are some dynamic
aspects of water.
In each path of the hydrologic cycle there are further more aspects involve, which are
 Transportation of water,
 Temporary storage and
 Change of state.
For example:
The process of rainfall includes the change of state and transportation of water.
Ground water movement includes the temporary storage and transportation aspects.
Various Aspects or paths of Hydrologic cycle:
 Evaporation from ocean,
 Raindrop evaporation,
 Interception,
 Transpiration,
 Evaporation from land and water bodies,

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 Surface runoff,
 Infiltration,
 Ground water,
 Deep Percolation.
The sequence of events describe above is the very simple form of a complex cycle that
has been taking place since the formation of earth. It is a continuous recirculating cycle
because there is neither a beginning nor an end or a pause. However, the convenient
starting point to describe the cycle is from the oceans.
Engineering Applications of hydrologic cycle:
The knowledge of hydrologic cycle is important in the design of projects dealing with water
supply, irrigation, coastal works, and salinity control etc.
Terms related to Contouring | Objects of Contouring |
Uses of Contour maps | Characteristics of Contours |
Methods of Contouring
Contouring:
1. Contour line
The intersection of ground surface and level surface is called contour line.
2. Contour interval
The perpendicular distance between two successive contours is known as contour
interval.
3. Horizontal equivalent
The horizontal distance between two successive contours is known as horizontal
equivalent
Objects of contouring:

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In engineering projects knowledge of contouring is important for determining nature of
ground surface.
Uses of contour maps
1. Ground surface is examined by it.
2. Its widely used in site selection.
3. Storage power of reservoir is calculated.
4. Two distinct stations are visible or not is determined.
5. Catchment can be determined by drawing in any direction.
Characteristics of contours
1. At top of hills contour lines are near to each other.
2. If contour lines are equally spaced it represents a uniform slope.
3. Contour lines never meet each one another.
4. Contours that are close to each other represents depressions.
5. Depression between summits is called saddles.
Methods of contouring
There are two methods of contouring
1. Direct method.
2. Method of interpolation.
3. Indirect method.
Principles of Surveying
Principles of Surveying
Followings are the principles of surveying which should be kept in mind while determining
the relative positions of points on the surface of earth:
To work from whole to part
Working from whole to part is done in surveying in order to ensure that errors and
mistakes of one portion do not affect the remaining portion. First step in the extensive
surveys such as topographic surveys, is to establish a system of control points with high
precision. For the horizontal control, the points are established by triangulation or precise

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traversing. To do this by triangulation, the area to be surveyed are divided in to large
triangles. These triangles are surveyed with greatest accuracy. These large triangles are
further divided in to small triangles which are surveyed with less accuracy. The object of
this system is to prevent the accumulation of errors, and to control minor errors.
On the other hand if we work from part to whole, small errors are magnified in the process
of expansion of survey. These errors become uncontrollable at the end.
Fix the positions by two independent process
To fix the positions of new stations by two independent process. The new stations are
fixed from points already fixed by linear measurements, angular measurements or by both
linear and angular measurements.
Definition of Change Point and Station
Change Point
It may be defined as:
A Change Point ( C.P) is a point which shows the shifting of the level. It is a point on
which fore and back sights are taken. Any stable and well defined object such as
boundary stone, curb stone, rail, rock, etc., is used as a change point. A Benchmark
may also be taken as change point. It is also known as turning point. (T.P)
Station
Any point whose elevation is to be determined is known as station. Or a point which is
to be established at a given elevation. It is the point where the staff is held not the point
where the level is set up.
Simple and Differential levelling
Simple levelling
When it is required to find the difference between two points which are visible from a
single position of level. Then the method used is simple levelling.
Suppose A and B are two points and the level is set up at approximately midway between
them, suppose at O. After the instrument is correctly levelled, the telescope is directed
toward the staff held vertically on A and focused. Reading at which Horizontal hair of the
diaphragm appears to cut the staff is taken. Ensure that bubble of the level is in center.
Then the staff is held vertically on B. Again reading is taken at point B from point O. Let

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the respective readings on A and B be 2.350 and 3.315 . The difference between these
readings give the difference of level between A and B which is equal to 3.315 m – 2.350
m = 0.965 m
If the reduced level of A is 100 m, then we can find the reduced level of B.
Height of instrument at O = R.L of A + 2.350 m
Height of instrument at O = 100 m + 2.350 m = 102.350 m
R.L of B = 102.350 m – 3.315 m = 99.035 m
Note
1. When the point is lower, the staff reading is greater. When the point is higher, the staff
reading is smaller.
2. The bubble must be in center while the readings are being taken.
3. If the true difference of level between two points is required, then level must be set up
exactly midway between them.
Differential levelling
This method is used in order to find the difference between two points which are far
apart or if the difference in elevation between them is too great or if there are obstacles
in between them.
In such case, it is necessary to set up level in several positions and to work in series of
stages. The method of simple levelling is applied on every stage. It is also known
as compound or continuous levelling.
Layout Of Simple Circular Horizontal curve | Degree of
Curvature | Length of Curve | Circular Curve Geometry
Layout of Simple Circular Curve :
The typical layout of simple circular curve is shown in the figure below.

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R = Radius of Circular Curve
BC = Beginning of Curve
(or PC = Point of Curvature)
EC = End of Curve
(or PT = Point of Tangency)
PI = Point of Intersection
T = Tangent Length
(T = PI – BC = EC – PI)
L = Length of Curvature

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(L = EC – BC)
M = Middle Ordinate
E = External Distance
C = Chord Length
Δ = Deflection Angle
Circular Curve Components
Properties of Circular Curve:
Degree of Curvature:
Traditionally, the “steepness” of the curvature is defined by either the radius (R) or the
degree of curvature (D).
Degree of curvature = angle subtended by an arc of length 100 feet.

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The diagram below is showing the degree of curvature.
If the arc length is 100 feet then the angle will be the degree of curvature as shown in
the figure below.

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Steepness of curve can be defined in term of radius as shown in the figure below.
R = 5730 / D
(Degree of curvature is not used with metric units because D is defined in terms of feet.)
Length of Curve:
For a given external angle (Δ), the length of curve (L) is directly related to the radius (R).
L = (RΔπ) / 180
As we know π / 180=1/57.3

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L = RΔ / 57.3
Where
R = Radius of Circular Curve
L = Length of Curvature
Δ = Deflection Angle
Conclusion :
From the above relation L = RΔ / 57.3 . It is concluded that larger the radius of curve
longer will be the curve.
Other Formulas for the Layout of Simple Circular Curve :
Tangent: T = R tan(Δ/2)

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Chord: C = 2R sin(Δ/2)
Mid Ordinate: M = R – R cos(Δ/2)
External Distance: E = R sec(Δ/2) – R
Circular Curve Geometry :
Objectives of triangulation | Classification of
Triangulation System
Objectives of triangulation:
The main objective of triangulation is to provide a number of stations whose relative
and absolute positions, horizontal as well as vertical, are accurately established. More
detailed survey is then carried out from these stations.Further objectives are given below
1. To establish accurate control for plane and geodetic survey of large areas.
2. To establish accurate control for photogrammetric survey.
3. To determine accurate locations of points in engineering works.

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Classification of Triangulation System:
Based on the extent and purpose of the survey, and consequently on the degree of
accuracy desired, triangulation survey is classified as
 First order (primary)
 Second order (secondary)
 Third order (tertiary)
First order
It is used to determine the shape and the size of the earth or cover vast area like whole
country with control points.
Second order
It is used to cover areas of a region, small country, province. It Consists of network within
the first order.
Third order
It serves the purpose of furnishing the immediate control of detailed engineering and
location survey.
Surveying
Surveying is the science of determining relative positions of objects on the
surface of the earth by taking measurements of distances, directions, and
elevations and plotting them to convenient reduced size on papers.
Basic principles : 1. Locating a point on the surface of the earth by at least
two reference points.
2. Working from whole to the part. In this system first a system of control
points are fixed with great precision.
Surveying is the science of map making. To start any development activity,
the relative positions of various objects in the area with respect to horizontal
and vertical axes through a reference point is required. This is achieved by
surveying the area. Earlier, the conventional instruments like chain, tape
and levelling instruments were used. In this electronic era, modern
electronic equipments like electronic distance meters (EDM) and total
stations are used, to get more accurate results easily.

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Preparing topo maps of talukas, districts, states and countries and showing
all important features like rivers, hills, forests, lakes, towns and cities in plan
and elevation (by contour lines) also forms part of surveying. When maps of
large areas are to be made corrections for earth curvature are to be made
for all measurements. Such survey is called geodetic surveying also.
Explain Tacheometric survey
Tacheometry is a branch of surveying in which the horizontal and vertical
distances are determined by angular observations with a tacheometer. The
chaining operations are altogether eliminated. Tacheometry is not as
accurate as in chaining.
The main instruments used in tacheometry is a tacheometer. Tacheometric
survey may be carried but by stadia hair system or tangential system.
What is Tapes
Tapes are used for more accurate measurement and are classified
according, to the material of which they are made.
For example
1. Cloth or linen tape
2. Metallic tape
3. Steel tape
4. Invar tape
Triangulation
It is the process of measuring the angles of a network of triangles formed by
stations marked on the surface of the earth.
Types of triangulation
1. Primary triangulation
2. Secondary triangulation
3. Tertiary triangulation
Different terms used in triangulation
1. True value
2. Observed value
3. True errors
4. Most probable error
5. Residual error
6. Weight of the observations
7. Laws of weights
Astronomy

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1. The celestial sphere : The imaginary sphere on which
heavenly bodies, i.e., stars, sun, moon etc. appear to lie is known
as celestial sphere.
2. The Zenith : The point on the celestial sphere above the
observer's station is known as the Zenith.
3. The Nadir : The point on the celestial sphere exactly below
the observer's station is known as the Nadir.
4. The Zenith-Nadir line : The Zenith, the observer's station
the centre of the earth and the Nadir all lie on a line which is
known as Zenith Nadir line.
5. The celestial horizon : The great circle of the celestial sphere
obtained by a plane passing through the centre of the earth and
perpendicular to the Zenith-Nadir line is known as the celestial
horizon.
6. The visible horizon : The small circle of the earth which is
obtained by visual rays passing through the point of observation
is known as visible horizon.
7. The sensible horizon : The small circle which is obtained by
a plane-passing through the observer's station and tangential to
the earth's surface and perpendicular to the Zenith-Nadir line at
the point of observation is known as the sensible horizon.
8. The terrestrial equator : The great circle of the earth the

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plane of which is perpendicular to its axis of rotation is known as
the terrestrial equator.
9. The terrestrial poles : The points at which earth's axis of
rotation meets the earth's surface, are known as the terrestrial
poles.
10. The celestial poles : The points at which earth's axis of
rotation on prolongation on either side meets the surface of the
celestial sphere are known as celestial poles.
11. Vertical circles : The great circles of the celestial sphere
passing through the Zenith and Nadir are known as vertical
circles.
12. The observer's meridian : The vertical circle which passes
through Zenith and Nadir of the station of the observation as well
as through the poles, is known as observer's meridian.
13. The prime vertical : The vertical which is perpendicular to
the observer's meridian and passes through the east and west
points of the horizon is known as the prime vertical.
14. North and south points : The projections of the elevated
north and depressed south poles on the horizon are known as
north and south points respectively.
15. East and west points : The points on which the prime
vertical meets the horizon, are known as east and west points.
These points may also be obtained by the intersection of the
equator and horizon.
16. Ecliptic : The great circle of the celestial sphere which the
sun appears to describe with earth as centre in the course of one
year, is known as ecliptic.
17. Altitude : The angular distance of a heavenly body above
the horizon, measured on the vertical circle passing through it, is
called altitude.
18. The azimuth : The angle between the observer's meridian
and the vertical circle passing through the celestial body and the
Zenith is known as azimuth.
19. The celestial latitude : The arc of a great circle
perpendicular to the ecliptic, intercepted between the celestial
body and the ecliptic is known as the celestial latitude of the
body.

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20. The celestial longitude : The arc of an ecliptic intercepted
between the great circle passing through the point of Aries (y)
and the great circle passing through the celestial body is called
celestial longitude.
360° of longitude = 14 hours of time
15° of longitude = 1 hour
15' of longitude = I minute
15" of longitude 1 second
Apparent time = Mean time + Equation of time
What is Bearing
Bearing is the horizontal angle which a line makes with some reference
direction, known as meridian. The reference direction may be any of the
following three :-
1. True meridian
2. Magnetic meridian
3. Arbitrary meridian
Bearing is of the following types :-
1. Whole circle bearing
2. Quadrantal bearing
3. Reduced bearing
4. Fore bearing
5. Back bearing.
Back bearing = Fore bearing ± 180°
Explain Compass survey
It is a survey conducted with the help of prismatic or surveyors' compass.
Unit of measurement is an angle. It is the difference in directions of two
intersecting lines.
Contouring
A contour is an imaginary line on the ground joining the points of equal
elevation.
Characteristics of Contours
1. Two contours of different elevations do not cross each other except in the
case of an over hanging cliff.
2. Contours of different elevations do not unite to form one contour except
in the case of a vertical cliff.
3. Contours drawn closer depict a steep and if drawn far apart it represent a
gentle slope.

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4. Contours equally spaced depict a uniform slope.
5. A contour at any point is perpendicular to the line of the steepest slope at
the point.
6. A contour must close itself or go out of the limit of the map.
7. A set of ring contours with higher values inside, depict a hill whereas a set
of ring contours with lower values inside, depict a pond or a depression.
8. When contours cross a ridge or V-shaped valley these form sharp V-
shaped across them.
9. The same contour must appear an both the sides of a ridge or a valley.
Explain Curves
Curves are regular bends provided in the lines of communication like roads,
railways and canals to bring about the gradual change of direction. They are
also used in the vertical plane at all changes of grade to avoid the abrupt
change of grade at the apex. Curves provided in the horizontal plane to have
the gradual change in direction are known as horizontal curves whereas
those provided in the vertical plane to obtain the gradual change in the
grade are known as vertical curves.
Explain Geodetic surveying
That survey, where the curvature of the earth is taken into account is called
geodetic surveying. It is known as trigonometrical survey.
Levelling is an important branch of surveying.
Principle of levelling :
Essentially a level consists of the following five parts
1. A telescope to provide a line of sight
2. A level tube to make the line of sight horizontal
3. Levelling head to bring the bubble in the centre of tube
4. A cross bubble tube to provide a horizontal plane
5. A tripod to support the instrument
Types of levels :
Following are commonly used levels-
1. Dumpy level
2. Wye level
3. Cooke's reversible level
4. Cushing's level
5. Modern Titing level of Indian office Pattern
Levelling Terminology :

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Level surface
Level line
Horizontal surface
Horizontal line
Vertical surface
Vertical line
Datum
Reduced level
Line of collimation
Back sight
Fore sight
Intermediate sight
Height of instrument
Changing point
Station
Bench mark
Parallax
Temporary adjustment of a level
Permanent adjustment of a level
Level book
Reduced levels
Reciprocal levelling
Explain Methods of Plane Tabling
1. Radiation : This method is used when distance are small.
2. Intersection : It is used when the distance between the point
and the instrument station is either too large or can not be
measured accurately due to field conditions.
3. Traversing
4. Re-section
The following are the four methods of orientations :
1. Orientation by compass
2. Orientation by back sighting
3. Orientation by three point problem
4. Orientation by two point problem
What is Offset

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It is the lateral distance of an object or ground feature measured
from a survey line. There are two types of offsets :-
1. Perpendicular offset
2. Oblique offset
Various instruments are used in chain survey.
They are (1) Chain (2) Arrows (3) Pegs (4) Ranging rods (5) Offset
rods (6) Plasterer's laths and whites (7) Plumb bob
The following are the precise instruments used for setting out
right angles :-
1. Cross staff
2. French cross staff
3. Adjustable cross staff
4. Optical square
5. Prism square
Explain Plane surveying
The survey where the effect of curvature of the earth is neglected assuming
the earth's surface to be plane is called plane surveying. Generally areas less
than 260 sq. km are treated as plane. For engineering works, this type of
survey is generally followed.
Positive errors are those which make the result too great and
negative errors make result too small.
What is Scale

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Scale is the fixed ratio that a distance on map bears with the corresponding
distance on the ground i.e.,1 cm = 10 m.
What is Stadia hair system
This system may further be divided into two different methods :
1. Fixed hair method
2. Movable hair method
What is Survey chain
It is the method of surveying in which the area is divided into a network of
triangles and the sides of the various triangles are measured directly in the
field with chain or tape and no angular measurement are taken.
Various chains used for the survey work are
1. Metric chains : They are available in lengths of 5, 10, 20 and
30 meter.
2. Gunless chain : They are available in 66 ft. length provided
with 100 links.
3. Engineer's chain : It is 100 ft. Ion with 100 links
4. Revenue chain : It is 33 ft. long provided with 10 links.
Tacheometric calculations
There are four cases of tacheometric calculations. They are
1. Staff held vertical
2. Inclined sights staff held vertical
3. Inclined sights upwards, staff held normal
4. Inclined sights downwards, staff held normal
Tangential method of tacheometry
1. Both angles being elevations
2. Both angles being depressions
3. One angle elevation and the other depression
What is Tie line
The line connects tie stations or subsidiary stations on the main survey lines
and is provided primarily with the object to facilitate taking offsets to objects
distant from the main lines.
What is Base line
The longest line of the main survey lines is designated as the base line.

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Uses of Contour Maps
1. To study the general character of the tract of the country without visiting
the ground.
2. To decide the most economical and suitable sites for engineering works
such as canal, sewer, reservoir, road, railway etc.
3. To determine the catchment area of the drainage basic and hence the
capacity of the proposed reservoir.
4. To compute the earth work required for filling or cutting along the linear
alignment of projects such as canals, roads etc.
5. To ascertain the intervisibility of the points.
6. To trace a contour gradient for road alignments.
7. To draw longitudinal sections and cross-sections to ascertain the nature of
the ground.
8. To calculate water capacities of reservoirs.
Corrections in linear measurements
For precise measurements, the following corrections are generally applied :-
1.Correction for standard length
2. Correction for alignment
3. Correction for slope
4. Correction for tension
5. Correction for temperature
6. Correction for sag.
Define Errors
Errors may arise due to any of the following reasons-
1. Instrumental : Imperfect or faulty adjustments of
instruments cause instrumental error.
2. Personal : Errors clue to lack of perfection of human sight in
observing are called personal errors.
3. Natural : Errors due to variations in natural phenomena such
as temperature, humidity, refraction, magnetic declination etc.
are called natural errors.
Errors in survey work may be classification as :
1. Mistakes : These errors arise from inattention, inexperience,
carelessness and misjudgement or confusion in the mind of an
observer.
2. Cumulative errors : These are the errors which under the
same conditions, will always be of the same size and sign.

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3. Accidental or compensation errors : These are the errors
which remain even after mistakes and cumulative errors have
been eliminated and are caused by a combination of reasons over
which the observer has no control.
Hydrographic survey
Survey carried out to depict accurately fathoms and other
topographical features of large water bodies like sea rivers, lakes,
bays etc. is known as Hydrographic survey.
The requirements of hydrographic survey
1. Close soundings
2. Continuous record of meteorological conditions
3. Position of least depth on shoals
4. Position of breakers
5. Position of light vessels and buoys
6. High and low water line
7. Tide tables
8. Measurement of ideal sream and currents
9. Observation magnetic variations
What is Magnetic compass
Three types of compasses are commonly used which are :-
1. Prismatic compass
2. Surveyor's compass
3. Transit compass
What are Minor instruments
The main minor instruments are as follows :
1. Hand level
2. Clinometer
3. Abney's level
4. Tangent clinometer
5. Ceylon chat tracer
6. Box sextant
7. Pantagraph
8. Planimeter

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Permissible errors in chaining for measurements made
with
1. lnvar tape, spring balances, thermometers = 1 in 10,000
2. Steel tape, plumb bob = 1 in 2000
3. Tested chain, plump bob = 1 in 1000
4. Chain under average conditions = 1 in 500
Explain Plane table survey
Plane table survey is a method of surveying in which field work
and office work are done simultaneously on a plane table.
Following instruments are used in plane tabling.
1. Plane Table
2. Alidade
3. Plumbing fork and plumb bob
4. Spirit level
5. Compass
6. Rain proof cover for the plane table
7. Chain or tap
8. Ranging rods
9. Drawing sheets
10. Drawing, equipment
What is Representative fraction (R.F.
The ratio of map distance to the corresponding ground distance is called
representative fraction. It is independent of unit of measurement.
Sexagesimal system
In this system
1 circumference = 360° (degrees)
1 degree 60' (minutes)
1 minute = 60" (seconds)
What is Station
The end points of a chain line are called station and the station on beginning
or end of main chain line is known as main survey station. The tie station
are selected anywhere on the chain line.

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Civil Engineering Land Surveying Basics
The history of surveying started with plane surveying when the first line was measured.
Today the land surveying basics are the same but the instruments and technology has
changed. The surveying equipment used today are much more different than the simple
surveying instruments in the past. The land surveying methods too have changed and the
surveyor uses more advanced tools and techniques in Land survey.
Civil Engineering Surveying
Definition
The process of determining by measurement, the relative positions of points above, on, or
beneath the earth surface, in order to produce map or plan (which shows feature of the
surface) in horizontal or vertical plane. The Term surveying refers to those measurements
or operation, which deal in production of map or plan in horizontal 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 earth.
 Determining position of points in vertical plane.
Surveying and leveling are considered as distinct operations, however in broad sense, the
term surveying includes leveling.
Objectives of Survey
The Primary objective of survey is the preparation of plan and map of an area. The result
of survey in the form of data when plotted and drawn on paper, we get a plan/map. If the
scale is large it is called Plan. E.g. Plan of a Building, say 1:100. If the scale is small, it is
called Map. E.g. Map of Pakistan, say 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

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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)
Principle of Surveying
1. To work from the Whole to the Part, not from the part to the Whole. e.g. set out the main
frame first, and add details onto the frame. Object of this system is to prevent
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
Station can be fixed from points already fixed
By
1. Linear measurement
2. Angular measurement or
3. Both
Common Definitions in Surveying
Leveling Definition:
Levelling is the most widely used method of obtaining the elevations of ground points
relative to a reference datum and is usually carried out as a separate procedure to those
used in fixing planimetric position.
The basic concept of levelling involves the measurement of vertical distance relative to a
horizontal line of sight. Hence it requires a graduated staff for the vertical measurements
and an instrument that will provide a horizontal line of sight.
Level line
A level line or level surface is one which at all points is normal to the direction of the force
of gravity as defined by a freely suspended plumb-bob. As already indicated in Chapter 1
during the discussion of the geoid, such surfaces are ellipsoidal in shape. Thus in Figure
2.1 the difference in level between A and B is the distance A'B.
Horizontal line
A horizontal line or surface is one which is normal to the direction of the force of gravity
at a particular point. Figure 2.1 shows a horizontal line through point C.

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Datum
A datum is any reference surface to which the elevations of points are referred. The most
commonly used datum is that of mean sea level (MSL). In the UK the MSL datum was
fixed by the Ordnance Survey (OS) of Great Britain, and hence it is often referred to as
Ordnance Datum (OD). It is the mean level of the sea at Newlyn in Cornwall calculated
from hourly readings of the sea level, taken by an automatic tide gauge over a six-year
period from 1 May 1915 to 30 April 1921.
Bench mark (BM)
In order to make OD accessible to all users throughout the country, a series of permanent
marks were established, called bench marks. The height of these marks relative to OD has
been established by differential levelling and is regularly checked for any change in
elevation.
Levelling in Engineering Survey
Definition:
Levelling is the most widely used method of obtaining the elevations of ground points
relative to a reference datum and is usually carried out as a separate procedure to those
used in fixing planimetric position. The basic concept of leveling involves the measurement
of vertical distance relative to a horizontal line of sight. Hence it requires a graduated staff
for the vertical measurements & an instrument that provides a horizontal line of sight.
Types of Levelling Survey are:
1. Precise or Geodetic Levelling
2. Ordinary or Simple Levelling
Methods of Levelling
Methods of levelling may be direct e.g.
1. Simple Levelling
2. Differential Levelling
3. Profile Levelling
4. Cross Sectioning
5. Reciprocal Levelling
6. Precise levelling
7. Check Levelling
8. Fly Levelling

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Or may be indirect e.g
1. Trigonometric Levelling
2. Barometric Levelling
3. Hypsometry
Levelling procedures
(a) Setting up
1. Backsight and foresight distances should be approximately equal to avoid any errors
due to collimation, refraction or earth curvature.
2. Distances must not be so great as to not be able to read the graduations accurately.
3. The points to be observed must be below the level of the instrument, but not lower
than the height of the staff.
(b) Elimination of parallax
1. Parallax is the apparent movement of the image produced by movement of the
observer's eye at the eyepiece.
2. It is eliminated by focusing the telescope on infinity and then adjusting the eyepiece
until the cross-hairs appear in sharp focus. The setting will remain constant for a
particular observer's eye.
(c) Booking
1. Level books or loose-leaf levelling sheets shall be numbered and indexed in a
register.
2. Details of the site, work, date, observer, chainman, booker, weather, wind,
instrument and any other relevant items shall be entered.
3. Enter the first observation (which is on a known point) in the Backsight column,
and sufficient detail in the Remarks column to identify it. Enter the point's R.L. zero
from the site register or plate on the BM, etc.
4. Enter all other points on subsequent lines as intermediates except the point chosen
as the foresight. Identify them in the Remarks column as above. Enter the foresight
on a further line in the Foresight column.
5. Change the instrument to the next setup. Enter the following backsight on the same
line as the previous foresight but in the Backsight column.
6. Repeat the above procedure at each setup on the outward run then reverse it to work
back to the starting point on the return run. The furthest point out is treated as for
all other change points.

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Types of Levels - Instruments used for Levelling
a. Builder's/Engineer's Level:
As implied by the name, these are used by builders and engineers. Their design is basically
as described earlier, and they use graduated staffs in which the smallest graduation is 1cm.
Millimeters must be estimated, and the accuracy of a single reading will be about 2-3mm.
b. 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 photo detector 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
up to 100m.
c. 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.
Errors in Levelling
1. Collimation Error
2. Error due to Curvature & Refraction
3. Instrumental Errors
Curvature and Refraction

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Curvature and Refraction
Curvature of the earth:
The earth appears to “fall away” with distance. The curved shape of the earth means that
the level surface through the telescope will depart from the horizontal plane through the
telescope as the line of sight proceeds to the horizon.
This effect makes actual level rod readings too large by:

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where D is the sight distance in thousands of feet.
Effects of Curvature are:
 Rod reading is too high
 Error increases exponentially with distance
Atmospheric Refraction:
Refraction is largely a function of atmospheric pressure and temperature gradients, which
may cause the bending to be up or down by extremely variable amounts.
There are basically three types of temperature gradient (dT/dh):
1. Absorption: occurs mainly at night when the colder ground absorbs heat from the
atmosphere.
o This causes the atmospheric temperature to increase with distance from the
ground and dT/dh > 0.
2. Emission: occurs mainly during the day when the warmer ground emits heat into
the atmosphere, resulting in a negative temperature gradient, i.e. dT/dh < 0.
3. Equilibrium: no heat transfer takes place (dT/dh = 0) and occurs only briefly in the
evening and morning.
4. The result of dT/dh < 0 is to cause the light ray to be convex to the ground rather
than concave as generally shown.
o This effect increases the closer to the ground the light ray gets and errors in
the region of 5 mm/km have resulted.
The atmosphere refracts the horizontal line of sight downward, making the level rod
reading smaller. The typical effect of refraction is equal to about 14% of the effect of
earth curvature.
Combined Effect of Curvature and Refraction in Survey
The combined effect of curvature and refraction is approximately

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The formula for computing the combined effect of curvature and refraction is:
C + R = 0.021K2
Where C = correction for curvature
R = correction for refraction
K = sighting distance in thousands of feet
Correlations for various distances
Distance Correction
100' 0.00021'
200' 0.00082'

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500' 0.0052'
700' 0.01'
1 mile 0.574'
How to eliminate error due to Curvature and Refraction
1. Proper field procedures (taking shorter shots and balancing shots) can practically reduce
errors
2. Wherever possible, staff readings should be kept at least 0.5 m above the ground,
3. Using short observation distances (25 m) equalized for back sight and foresight
4. Air below is denser than air above Air below is denser than air above, Line of sight is
bent downward which Negates earth curvature error by 14%.
5. Simultaneous Reciprocal Trigonometrical Heightening
6. Observations made at each station at exactly the same time, cancels the effects of
curvature and refraction
Scale and Distortion of a Vertical Photograph
Scale of a Vertical Photograph:
The scale of a photograph is the ratio between the dist measured on the photograph and
the ground distance between the same two points.
Difference between map and photograph:
MAP: Orthographic projection
 scale in uniform.
PHOTOGRAPH: Prospective view
 scale varies form point to point with variation in elevation.
The scale of the photograph is expressed as a representative fraction. (A scale having the
importance that we can take it in any unit). Knowing the height of the airplanes above the
datum and the focal length of the camera. The scale of the photograph can be dot. If the
ground were level as shown in figure by the dotted line A’D the scale of the photograph
would be.
From similar = S (scale) (1)

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The drawing horizontal plane through A and B the scale at A and B will Be
(2)
(3)
The scale of line ab, assuming an elevation AB equal and then.
The scale will become equal to (4)
This is now the scale which is app to both the pts A and B.
From eq. 2 and 3 it is apparent that photo scale increases at higher elves and dec at lower
elev. This concept is seen graphically in figure (2). Ground lengths AB and CD are equal
but photo distances ab and cd are not, cd being longer and at larger scale then ab due to the
higher elves of CD. Average photo scale is obtained by determining ground elevation of
the area photograph. If N is the number of points considered with ground heights h1,h2---
---- hn then average photo scale is given by
Scale for the whole photograph
Where Havg =
As the scale of the photograph depends on the height ‘H’ of the camera above ground, any
variation in ‘H’ will change the scale. It is therefore essential that the aeroplane flies at the
constant variation.
Use of an average photo scale is frequently desirable but must be accepted with caution as
an approximation. Scale of a photograph can be determined if a map is available of the
same area. This method doesn’t require the focal length and flying height to be known, it
is necessary only to measure on a photograph a dist b.t two well defined pts identifiable on
map. The photo scale is then calculated using the following relationship.

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PHOTO SCALE =
Scale at average elevation of the two points considered.
NOTE: The numerator and denominator must be expressed in the same units.
Distortion due to height (or Relief) on the vertical Photograph:
Consider the sight of a high building BC in the figure and it consequent image bc on the
negative. B is vertically above C and in plane the two coincides but on photograph the sight
of the building cb would by observed as well as the roof of this building would appear to
be leaning outwards from the centre of the photograph.
Relief distortion on a vertical photograph occurs along radial line form the principal point
an increases in magnitude with greater distance to the image. From similar triangles EBO
and obv
(1)
Similarly, from vco and VCD
(2)
Dividing eq 1 by 2
Thus distortion due to height Bc

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(A)
(b)
The expressions A and B hold good for a truly vertical photograph.
Levelling Tools & Equipment
The vertical measuring equipment in surveying are major summed into two but other
instruments still exist. The two major ones are:
 Measurement by surveying levels
 Barometric – pressure devices
These two major groups of instruments are exclusively used for determining vertical (as
well as horizontal) levels or elevations.
Surveying Levels:
There are four types of surveying levels:
1. The wye, or the dumpy level (see Fig. 10 & 11)
2. The tilting level,
3. the self – leveling level; and
4. Digital electronic level
Dumpy Level:
The first type consists of a telescopic sight. Like that of a transit but usually of slightly
higher magnification, to which a long spirit level (see fig. 11) is attached and adjusted so
that the bubble centres when the line of sight is horizontal. A dumpy level is also known

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as builder’s auto level, leveling instrument or automatic level. It is an optical instrument
used in surveying and building to transfer measure or set horizontal levels.
The level instrument is set up on a tripod and, depending on the type, either roughly or
accurately set on a leveled condition using foot screws (Leveling screws). The operator
looks through the eyepiece of the telescope while as assistant holds a tape measure or
graduated staff vertical at the point under measurement. The instrument and staff are used
to gather and / or transfer elevation (levels) during site surveys. Measurement generally
starts from the benchmark with known height determined by a pervious survey, or an
arbitrary point with an assumed height. A dumpy level (Fig 10) is an older-style
instrument that requires skilled use to set accurately. The instrument requires to be set
level in each quadrant to ensure it is accurate through a full 360o traverse.
A variation in the dumpy and one that was often used by surveyors, where greater
accuracy and error checking was required, is a tilting level. This instrument allows the
telescope to be effectively flipped through 180o, without rotating the head. The telescope
is hinged to one side of the instrument’s axis; flipping it involves lifting to the other side
of the central axis (thereby inverting the telescope). This action effectively cancels out
any errors introduced by poor setting procedure or errors in the instrument’s adjustment.
The tilting level is similar to dumpy but the telescope with main bubble attached can be
separately tilted up and down by means of a micrometer screw, given it greater accuracy.
Self Level:
The self – leveling level is similar to tilting level except that it has no micrometer screw.
Instead, self –leveling level contains an internal compensator mechanism (a swinging
prism or pendulum) that, when set close to level, automatically removes any remaining
variation from level. This automatically reduces the need for setting the instrument for
leveling as in the case of dumpy and tilting level. Self leveling instruments are highly
preferred instrument in surveying due to ease of use and minimal rapid set up time
consuming.
Digital Level:
A digital electronic level is another leveling instrument set up normally on a tripod and it
reads a bar – coded staff using electronic laser methods. The height of the staff where the
level beam crosses the staff is known on a digital display. This type of level removes
interpolation of graduation by a person, thus removing a source of error and increasing
accuracy.

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The level rod or level Staff:
A level staff, also called leveling rod, is a graduated wooden or aluminum rod, the use of
which permits the determination of differences in metric graduation as the left and
imperial on the right (see fig. 12) leveling rods can be one piece, but many are sectional
and can be shortened for storage and transport or lengthened for use. Aluminum rods may
adjust length by telescoping section inside each other, while wooden rod sections are
attached to each other with sliding connections or slip joints. There are many types of
rods, with names that identify the form of the graduations and other characteristics.
Marking can be in imperial or metric units. Some rods are graduated on only one side
while others are marked on both sides. If marked on both sides, the markings can be
identical or, in some cases, can have imperial units on one side and metric on the other
side.
Fig. 12. A 2-sided Modern Survey Levelling Rod
Aneroid Barometers:
Vertical measurements can be approximately determined by finding the different in
barometric pressure at the two elevations. Aneroid barometers and hypsometers measure
such differences. Aneroid barometers are devices in which changes in atmospheric
pressure cause a needle to move over a scale. Instruments of this type designed for
surveying are called altimeters. A type that records time along with pressures is usually
placed at the points where measurements of elevation are desired. When the second
instrument is read, the time is recorded, so that the simultaneous reading of the base
instrument can be selected (see fig. 14 (a) and 14 (b)). The difference of the two readings
must be corrected to the unit weight of the air, which is estimated from the barometric
pressure, temperature and humidity.

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Fig. 14 (a) An Old Aneroid Barometer Fig. 14 (b) A modern Aneroid Barometer
More accurate results independent of the unit weight of the air can be obtained by the two
– base method. Recording aneroid are placed at two bases, preferably one higher and
another lower than the elevations to be determined. Each field reading is adjusted in
proportion to the relative height above and below the two bases, so that the sum of the
two heights equals the known difference in the height between the bases. Within a radius
of ten miles (16 kilometers) this method gives elevations within about two feet 0.6
meters).
Hypsometers:
A hypsometer is an instrument for measuring height or altitude. Many different physical
principles may be used. A simple scale hypsometer allows the height of a building or tree
to be measured by sighting across a ruler to the base and top of the object being
measured, when the distance from the object to the observer is known. A pressure
hypsometer (as shown in Fig. 15) employs the principles that the boiling point of the
liquid is lowered by diminishing the barometric pressure, and that the barometric pressure
varies with the height of the point of observation. The instrument consists of a cylindrical
vessel in which the liquid , (usually water) is boiled and surmounted by a jacketed
column in the outer partitions of which the vapor circulates, while in the central one a
thermometer is placed. To deduce the height of the station from the observed boiling
point, it is necessary to know the relationship existing between the boiling point and
pressure, and also between postmasters use the combination of a laser range finder and a
clinometer to measure distances to the top and bottom of objects, and the angle between
the lines from the observer to each to calculate height.

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Fig. 15. Hypsometer
Plane table:
This shows a plane table with part of the surface of the table cut away to show the
mounting the tripod. The mount allows the table to be leveled on the table; the alidade
with telescope sight is seen in Fig 16. A plane table consists of a smooth table surface
mounted on a sturdy base. The connection between the table top permits one to level the
table precisely, using bubble levels, in a horizontal plane. The base, a tripod, is designed
to support the table over a specific point on land. By adjusting the length of the legs, one
can bring the table level regardless of the roughness of the terrain

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Usably, a plane table is set over a point and brought to precise horizontal level. A
drawing sheet is attached to the surface and an alidade is used to sight objects of interest.
The alidade, which is a modern example of an instrument, “a rule” with a telescopic sight
can then be used to construct a line on the drawing that is in the direction of object of
interest. By using the alidade as a surveying level, information on the topography of the
site can be directly recorded on the drawing as elevations. Distances to the objects can be
measured directly or by the use of stadia marks in the telescope of the alidade.
Fig. 13. A Plane Table
Distance Measuring Equipment
Distance is measured by mechanical devices (chain or steel tape) or by electronic means.
1. Chain tape:
The chain tape is also referred to as the Günter’s chain. Gunter’s chain, the 300 –year-
old measuring instrument by which all survey measurement in the English – speaking
countries and much of it elsewhere was done. It has been superseded by the steel tape and
electronic equipment. Gunter’s chain is 66 feet long; 80 chain equal to one mile, and 10
square chains equals an acre. The chain is subdivided into 100 links. A rod or perch was
25 links. Each link was a short section of wire connected to the next by a loop. At each
end of the chain was a brass handle. The 66 – foot unit is still called a chain and is still in
use in property descriptions and in the public land system. The Gunter chain is generally
used in taking short and detailed length and breadth of a school farmstead.

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2. The Steel Tape:
A graduated steel ribbon, or a flat wire, with handles at each. It is a basic modern means
of measuring distance. Its length is taken as a straight line distance between the two end
marks at 68°F (20°C) because the tape actual length varies with different types of
suppose different tensions, and different temperatures. In the port, the tension, the
temperature and the difference in height of the two end marks are recorded and the
measured length corrected accordingly.
In most routine surveys, the tape is held at hand at the end, kept high enough to clear
ground objects, made horizontal by estimation, and placed in the direction of
measurement. The desired tension is estimated, and the positions of graduations are
brought to the ground marks by plumb bobs. Sometimes the air temperatures are
recorded. For higher accuracy, tripods or other supports are employed, or the tape is fully
supported on smooth surfaces. The shops and temperature of the tape are determined.
Then, the tension is regulated with a spring balance.
Eliminating temperature problems in steel tapes
When especially accurate measurements are necessary, particularly for base lines in a
triangulation system, a steel tape must be used at night or when the sky is over cast,
otherwise radiant heat will make it impossible to determine tape temperature. Tapes made
of invar avoid this difficulty. Invar is a steel alloy with an extremely low coefficient of
thermal expansion (about Fahrenheit). With such a tape, a temperature difference of 10°F
(5.6°C) from the design temperature would result in an error of only about 1/20 of an
inch (1.3 millimeters) in 1,000 feet (305 meters). Unfortunately, Invar tapes are easily
damaged for general use. Before the introduction of invar, iron bars immersed in melting
ice were used for daytime measurements.

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3. Electronic Instruments:
Sir Robert Watson – Watt, a Scottish physicist working in England, introduced an
electronic pulse – type instrument in 1935 called hiran. It measures distances over water
between land survey stations obscured from each other by the earth’s curvature. An
airplane high enough to be visible from both stations crosses the line between them while
sending out a series of pulses. These are automatically relayed back to the plane from
each station. The minimum sum of distance represented by the timed returns is chosen,
and the nearby sums are corrected to its average. The result is corrected for the altitude of
the plane and the refraction of the atmosphere, and the final value is taken as a distance
between the two stations. The electronic distance equipment is developed in phase – shift
system.
The phase – shift type of system was first developed in 1948 and gives very accurate
results. The process is comparable to conventional radio transmission, in which the
carrier frequency is modulated by radio frequencies that the receiver makes audible. In
phase – shift devices, the carrier frequency is either.
 Light beam (generated by laser or an electronic light beam) or;
 Radio beam (an ultrahigh frequency radio beam)
The light beam requires a clear line of sight, while the radio can penetrate fog, haze,
heavy rain, dust, sand storms, and some foliage. However, both types have a transmitter –
receiver at one survey station. At the remote station, the light uses a set corner mirrors;
but the high – frequency type utilizes a transmitter (requiring an operator) identical to a
transmitter – receiver at the original station. A corner mirror has the shape of the inside as
a cube. It returns light towards the source from whatever angle it is received, within
reasonable limits. A retransmission must be aimed at the transmitter receiver. In both
types of instrument, the distance is determined basically by the length of time it takes the
radio or light beam to travel to the target and back.
Shift in phase of modulating signals:
The elapsed time is determined by the shift in phase of the modulating signal during its
travels. Electronic circuitry detects this phase shift and converts it very accurately into the
exact fraction of small unit distance. By using several frequencies for the modulator
signal, the total distance can be computed.

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4. Total Station as Modern Equipment of Distance Measurement:
A total station is an electronic / optical instrument used in modern surveying. It is also
used by archaeologists to record excavations as well as by police crime scene
investigators, private accident deconstructionists and insurance companies to take
measurement of scenes. The total stations is an electronic theodolite (Transit) integrated
with an instrument to a particular spatial entity. Some models of total station included.
 Internal Electronic Data Storage (IEDS), to record distance
 Horizontal angle model
 Vertical angle measured model
Data collector Model – which is hand- held computer equipped to write these
measurements to an external data collector.
Angles and distances are also measured from the total station to points under survey, and
the coordinate (X, Y, and Z or northing, easting and elevation) of surveyed points relative
to the total station position are calculated using trigonometry and triangulation. Data can
be down loaded from the total station to a computer and application software used to
compute results and generate a map of the surveyed area.
Some total stations also have a GNSS interface (Global Navigation Satellite System
Interface) which combines the advantages of these two technologies (GNSS line of sight
not required between measured points, Total station – high precision especially in the
vertical axis compared with GNSS) and reduce the consequences of each technology’s
disadvantages (GNSS – Poor accuracy in the vertical axis and lower accuracy without
long occupation period, Total station – requires line of sight observation and must be set
up over a known point or with line of sight to two or more points with known location).
Measurement of distance is accomplished with a modulated microwave or infrared carrier
signal generated by a small solid –state emitter within the instrument’s optical path, and

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reflected by a prism reflector or the object under survey. The modulation pattern in the
returning signal is read and interpreted by the on board computer in the total station. The
distance is determined by emitting and receiving multiple frequencies, and determining
the integer number of wave lengths to the target for each frequency. Most total station use
purpose built glass porro prism reflectors for the EDM signal, and can measure distances
to a few kilometers. A typical total station can measure distances to about 3 milimeters or
1/1000th
of a foot. However reflector in a total station can measure distances to any object
that is reasonably light in colour, to a few hundred metres. But, robotic total stations
allow the operator to control the instrument from a distance via remote control. This
eliminates the need for as assistant staff member as the operator holds the reflector and
controls the total station from the observed point.
5. Micrometer:
A micrometer is an instrument for measuring the size and distance of distant objects.
Distant in this sense means a length that can not be readily measured by calibrated
instrument. The optical version of this instrument used two mirrors on a common extant.
By aligning the object on the mirrors using a precise vernier, the position of the mirrors
could be used to compute the range of the object. The distance and the angular size of the
object would then yield the actual size. The Micrometer Interferometer Surveyor is a
Commercial GPS-based system for performing geodetic measurements.
Horizontal and Vertical Curves in Surveying
Definition:
Curves are provided whenever a road changes its direction from right to S (vice versa) or
changes its alignment from up to down (vice versa). Curves are a critical! element in the
pavement design. They are provided with a maximum speed limit that should lie followed
very strictly. Following the speed limit becomes essential as the exceed in speed may
lead to the chances of the vehicle becoming out of control while negotiating a turn and
thus increase the odds of fatal accidents. Also, it is very necessary that appropriate safety
measures be adopted at all horizontal and vertical curves to make the infrastructure road
user friendly and decrease the risks of hazardous circumstances.
The low cost safety measures that can be adopted at curves included chevron signs,
delineators, pavement markings, flexible posts, fluorescent strips, road safety barriers,
rumble strips etc.

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Types of Curves
There are two types of curves provided primarily for the comfort and ease of the motorists
in the road namely:
1. Horizontal Curve
2. Vertical Curve
Horizontal Curves
Horizontal curves are provided to change the direction or alignment of a road. Horizontal
Curve are circular curves or circular arcs. The sharpness of a curve increases as the radius
is decrease which makes it risky and dangerous. The main design criterion of a horizontal
curve is the provision of an adequate safe stopping sight distance.
Types of Horizontal Curve:
Simple Curve:
A simple arc provided in the road to impose a curve between the two straight lines.
Compound Curve:
Combination of two simple curves combined together to curve in the same direction.
Reverse Curve:
Combination of two simple curves combined together to curve in the same direction.
Transition or Spiral Curve:
A curve that has a varying radius. Its provided with a simple curve and between the simple
curves in a compound curve.
While turning a vehicle is exposed to two forces. The first force which attracts the vehicle
towards the ground is gravity. The second is centripetal force, which is an external force
required to keep the vehicle on a curved path. At any velocity, the centripetal force would
be greater for a tighter turn (smaller radius) than a broader one (larger radius). Thus, the
vehicle would have to make a very wide circle in order to negotiate a turn.
This issue is encountered when providing horizontal curves by designing roads that are
tilted at a slight angle thus providing ease and comfort to the driver while turning. This
phenomenon is defined as super elevation, which is the amount of rise seen on a given
cross-section of a turning road, it is otherwise known as slope.

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Vertical Curves
Vertical curves are provided to change the slope in the road and may or may not. be
symmetrical. They are parabolic and not circular like horizontal curves. Identifying the
proper grade and the safe passing sight distance is the main design criterion of the vertical
curve, iln crest vertical curve the length should be enough to provide safe stopping sight
distance and in sag vertical curve the length is important as it influences the factors such
as headlight sight distance, rider comfort and drainage requirements.
Types of Vertical Curve:
Sag Curve
Sag Curves are those which change the alignment of the road from uphill to downhill,
Crest Curve/Summit Curve
Crest Curves are those which change the alignment of the road from downhill to uphill. In
designing crest vertical curves it is important that the grades be not] too high which makes
it difficult for the motorists to travel upon it.
Surveying Dictionary Words Starting from A
Absolute Accuracy
A measure which indicates how closely the coordinates of a point in Ordnance Survey
map data agree with the true National Grid coordinates of the same point on the ground.
As the true position can never be known exactly, the statistic is quoted relative to the best
known position determined by precise survey methods.
Absolute Coordinates
A coordinate pair or triplate measured directly from the origin of the coordinate system in
which it lies and not to any other point in the system.
Abstraction
The process of selection, generalisation and aggregation.
Acre
It is a Unit of area measuring equal to 43,560 square feet.

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Accuracy
The closeness of the results of observations, computations or estimates to the true values
or the values accepted as being true. Accuracy relates to the exactness of the operation by
which the result is obtained.
Accuracy Ratio or Error Ratio
Error ratio is a means of expressing the magnitude of the error of the survey in relation to
the distance traversed by the survey. Intuitively, a unit of error is of greater importance in
a short traverse than in a longer traverse. The error ratio is expressed as the quotient of
the absolute value of the error and the distance traversed.
Add Tape
An add tape has an additional major division at the head, beyond the zero mark of the
tape, which is subdivided into finer graduations, usually in tenths of a foot (or meter),
sometimes in hundredths. The use of this tape requires that the minor reading be added to
the major division reading.
Adjacent
Near to but not reaching or contacting.
Adjustments
Since all real measurements are imperfect, some amount of error will accumulate in the
course of a survey. That error can be logically distributed throughout the survey by
various adjustment procedures (i.e., manipulation of the data to produce a more logical
result). Adjustments can and should be done with any set of measurements for which
error can be assessed.
Aerial Photograph
A photograph taken by a camera mounted onto some form of flying object within the
Earth's Atmosphere. The resultant images are used in GIS as a background layer or used
by surveyors to digitize. It is called aerial photo or air photograph.
Aggregation
The grouping together of a "selected" set of like entities to form one entity. For example,
grouping sets of adjacent area units to form larger units, often as part of a spatial unit

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hierarchy such as wards grouped into districts. Any attribute data is also grouped or is
summarised to give statistics for the new spatial unit.
Aliasing
Visibly jagged steps along angled lines or object edges, due to sharp tonal contrasts
between pixels.
Altitude
The vertical angle between the plane of the horizon and the line to the object which is
observed. In photogrammetry, altitude applies to elevation above a datum of points in
space.
Angle Right
Clockwise horizontal angular measure.
Angle Left
Counterclockwise horizontal angular measure
Aneroid barometer
An instrument used to obtain heights above sea level by measuring atmospheric pressure.
Since atmospheric pressure varies with the height above or below sea level, the height
can be read directly from the height scale on the barometer
Arc
A locus of points that forms a curve that is defined by a mathematical function.
Area
A bounded contiguous two dimensional object which may or may not include its
boundary. Usually defined in terms of an external polygon or in terms of a set of grid
cells.
Artificial and modified surfaces
A General cover category consisting of roads and right-of-ways, buildings, parking lots,
farmsteads and ranch headquarters, urban and built-up areas, small built-up areas, rural

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transportation, and any other buildings that have a surface area greater than 1,000 square
feet.
Archaeological record
The archaeological record exists as a repository. Inside lie the decaying material remains
of ancient beings and civilisations. As archaeologists approach their work, they encounter
raw data from the archaeological record that serves as the source of their evidence to
interpret.
Assumed Datum
An assumed datum, which is established by giving a benchmark an assumed value (e.g.
100.000 m) to which all levels in the local area will be reduced. It is not good practice to
assume a level which is close to the actual MSL value, as it creates potential for
confusion.
Astronomic North
North by celestial observation of Sun or stars.
ATS
The Automated Title System is the computerised legal register of freehold land, State
tenure land and Reserve land in Queensland. The system also automates elements of the
document receiving, lodgement, tracking and registration processes.
Surveying Dictionary Words Starting from B
Backsight
A back-sight is a reading taken on a position of known coordinate(s). Since a survey
progresses from a point of known position to points of unknown position, a back sight is
a reading looking "backward" along the line of progress. The first reading of almost any
survey job should be a back-sight onto a fixed point of reference, usually a benchmark of
some sort.
Base Mapping
Usually associated with topographic mapping covering country or region at different
scales.

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Basic Land and Property Unit
The physical extent of a contiguous area of land under uniform property rights.
Basic Scale
The scale at which the survey is undertaken. For Ordnance Survey mapping, three scales
(1:1250 - urban, 1:2500 - urban and rural, 1:10 000 - mountain and moorland) are used.
Barren
A General cover category consisting of non-vegetated lands, including alkaline barrens,
un-reclaimed mined land, and other barren areas incapable of supporting vegetation.
Barren areas are non-vegetated either because the substrate will not support plant growth
or because the area is subject to frequent disturbance (e.g., scouring, flooding) that
prevents plant growth.
Barren land
A Land cover/use category used to classify lands with limited capacity to support life and
having less than 5 percent vegetative cover. Vegetation, if present, is widely spaced.
Typically, the surface of barren land is sand, rock, exposed subsoil, or salt-affected soils.
Subcategories include salt flats; sand dunes; mud flats; beaches; bare exposed rock;
quarries, strip mines, gravel pits, and borrow pits; river wash; oil wasteland; mixed barren
lands; and other barren land.
Baseline
A surveyed line usually several kilometres long. It is established with the utmost
precision available at the time. Surveys refer to the baseline for coordination and
correlation. The baseline accumulates distances throughout a triangulation network,
extending to other baselines, providing further integrated control
Beam compass
A drafting instrument used for drawing circles with a long radius. The point and scribe
are separate units, mounted to slide and clamp on a long beam.
Bearing
An angle measured clockwise from a north line of 0° to a given surveyed line.

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Bed
Land underlying a water body or roadway.
Benchmark
A bench mark (BM) is the term given to a definite, permanent accessible point of known
height above a datum to which the height of other points can be referred.
It is usually a stainless steel pin embedded in a substantial concrete block cast into the
ground. At hydrological stations rock bolts driven into bedrock or concrete structures can
be used, but structures should be used warily as they themselves are subject to settlement.
The locations of benchmarks shall be marked with BM marker posts and/or paint, and
recorded on the Station History Form.
BLM
Bureau of Land Management of U.S. Department of the Interior; formerly the General
Land Office (GLO).
Booking Values
Booking simply means "entering the field data in the field book". A format appropriate
for the type of survey should be followed to make interpretation and retrieval easy.
Boundary
The limit of a pre-defined and established area whose limit is determined by one or more
lines e.g. County area boundary, reservoir boundary. In other words, it is a border line or
exterior of a described parcel.
Bounded by
Informative term of location or limitation
Breakpoints
A breakpoint is a point where a change in some parameter of interest occurs. In
surveying, breakpoints are usually associated with changes in slope. A profile survey
which records only breakpoint stations can have equivalent (or even better) information
to a survey which records a regularly spaced set of stations, but with fewer entries (and
less time in the field).

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Browser
An application which gives the user the ability to view a graphic representation of
mapping data. The application would provide tools (e.g. pan, zoom) to aid this viewing. It
provides a visual representation of the mapping data, which may displayed at a variety of
resolutions dependent on the size of area being displayed.
Buffer
A zone of user-specified distance around a point, line or area. The generation of buffers
to establish the proximity of features is one of the most common forms of GIS analysis.
For example, it may be used to find all areas of industry less than 5km from a reservoir.
Building
A physical walled structure, connected to foundations, which has or will have a roof i.e.
this definition includes buildings surveyed at the foundation stage.
Surveying Dictionary Words Starting from C
Cadastre
A public register of land recording the extent and value of land parcels for
the purposes A dataset containing information related to land ownership
and rights. This usually takes the form of maps and descriptions of uniquely
identifiable land parcels. For each parcel, legal information such as
ownership, easements and mortgages are recorded more information can
be found on the HMLR web site.
Calibration
The act or process of comparing certain specific measurements in an
instrument with a standard.
Canal
Artificial open channel for waterway purposes.
Cardinal
North, South, East or West directions only.

Civil engineering land surveying basics pdf

Civil engineering land surveying basics pdf

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