surveying 2

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Prepared by R.Vijayakumar, B.Tech (CIVIL), CCET, Puducherry

SURVEYING – II

UNIT – I

1. What is Satellite Station?

A Subsidiary Station is established as near the true or principal station

as possible, the station so established is called a satellite station or eccentric

station or false station.

2. What is working from whole to part?

This means, when an area is to be surveyed, first a system of control

points is to be established covering the whole area with very high precision.

Then minor details are located by less precise methods. The idea of working

this way is to prevent the accumulation of errors and to control and localize

minor errors which, otherwise, would expand to greater magnitudes if the

reverse process is followed, thus making the work uncontrolled at the end.

3. What are the applications of triangulation?

Optical 3d measuring systems use this principle as well in order to

determine the spatial dimensions and the geometry of an item.

(Basically, the configuration consists of two sensors observing the

item. One of the sensors is typically a digital camera device, and the

other one can also be a camera or a light projector. The projection

centers of the sensors and the considered point on the object’s surface

define a (spatial triangle).

Within this triangle, the distance between the sensors is the base b and

must be known. By determining the angles between the projection

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rays of the sensors and the basis, the intersection point, and thus the

3d coordinate, is calculated from the triangular relations.

4. List the requirements in selecting a site as a baseline.

The site should be fairly level. If, however, the ground is sloping, the

slope should be uniform and gentle. Undulating ground should, if

possible be avoided.

The site should be free from obstructions throughout the whole of the

length. The line clearing should be cheap in both labour and

compensation.

The extremities of the base should be intervisible at ground level.

The ground should be reasonably firm and smooth. Water gaps

should be few, and if possible not wider than the length of the long

wire or tape.

The site should suit extension to primary triangulation. This is an

important factor since the error in extension is likely to exceed the

error in measurement.

5. What is meant by the strength of figure of a triangulation system?

The strength of figure is a factor to be considered in establishing a

triangulation system to maintain the computations within a desired degree of

precision. It plays also an important role in deciding the layout of a

triangulation system. It is based on the fact that computations in

triangulation involve use of angles of triangle and length of one known side.

The other two sides are computed by sine law.

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6. State the objectives of Triangulation survey?

To establish accurate control for plane and geodetic surveys of large

areas, by terrestrial methods.

To establish accurate control for photogrammetric surveys of large

areas,

To assist in the determination of the size and shape of the earth by

making observations for latitude, longitude and gravity, and

To determine accurate locations of points in engineering works such

as piers and abutments of long span bridges, fixing centre line,

terminal points and shafts for long tunnels, measurement of the

deformation of dams, etc.

7. Write some of the modern surveying equipments.

Total station is a theodolite with an Electronic Distance Measurement

Device. Total station has also been one of the reasons behind the drastic

change of technology in the surveying field. EDMD shifted the surveying

technology from optical mechanical devices to digital electronic devices. In

spite of just being distance measuring equipment, total station can also be

used for leveling when adjusted in a horizontal plane. Most of the ultra-

modern surveying devices are a combination of one or more of these

devices.

8. Define bench marking.

Bench mark 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 leveling or as a point upon which to close as a check.

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9. What is meant by Trignometrical leveling?

Trignometrical leveling is the process of determining the differences

of elevation of the given station from observed vertical angles and known

distance.

10. Define Signals.

A signal is a device erected to define the exact position of an observed

station. It may be classified as,

Daylight or Non luminous (opaque) signal

Sun or luminous signal

Night signal

UNIT – II

1. What are the functions of reverse curve?

Reverse curves are useful when laying out such things as pipelines,

flumes, and levees. The surveyor may also use them on low-speed roads and

railroads. They cannot be used on high-speed roads or railroads since they

cannot be properly super elevated at the PRC. They are sometimes used on

canals, but only with extreme caution, since they make the canal difficult to

navigate and contribute to erosion.

2. How curves are designated?

A curve may be designated either by the radius or by the angle

subtended at the centre by a chord of particular length. In India, a curve is

designated by the angle (in degrees) subtended at the centre by a chord of 30

metres (100 ft.) length. This angle is called the degree of curve (D). The

degree of the curve indicates the sharpness of the curve.

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3. Define vertical curve.

Vertical curves are equal-tangent curves, which mean that the

horizontal distance from the center of the curve to the end of the curve is

identical in both directions. Unequal-tangent vertical curves, which are

simply equal-tangent curves that have been attached to one another, are used

only infrequently.

4. Write the methods of setting out a circular curve.

Linear methods

By ordinates or offsets from long chord

By successive bisection of arcs

By offsets from the tangents

By deflection distances

Angular method

Rankine’s method of tangential angle

Two theodolite method

Tacheometric method

5. What is transition curve?

A curve of constantly changing radius, used to connect a circular arc

to a straight line or to an arc of different curvature.

6. What is sag or valley curves?

Valley curve or sag curves are vertical curves with convexity

downwards. They are formed when two gradients meet in any of the

following four ways:

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When a descending gradient meets another descending gradient

When a descending gradient meets a flat gradient

When a descending gradient meets an ascending gradient

When an ascending gradient meets another ascending gradient

7. Why the reverse curve is not provided in high speed ways?

According to the laws of mechanics, when a vehicle travels on a curve

it is forced outward by centrifugal force. It is impractical to balance

centrifugal force by super elevation alone, because for any given curve

radius a certain super elevation rate is exactly correct for only one driving

speed. Hence we cannot provide reverse curve in high speed ways.

8. List the various types of curve.

Simple curve

Compound curve

Reverse curve

Transition curve

Vertical curve

9. What are the functions of a transition curve?

Primary functions of a transition curves (or easement curves) are:

To accomplish gradual transition from the straight to circular curve,

so that curvature changes from zero to a finite value

To provide a medium for gradual introduction or change of required

super elevation

To changing curvature in compound and reverse curve cases, so that

gradual change of curvature introduced from curve to curve

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10. What are the uses of vertical Curves?

Allow smooth transition from one grade to another (driver comfort)

Provide adequate sight distance at junction of grades and for

overtaking (safety)

Provide satisfactory appearance (aesthetics)

UNIT – III

1. What are accidental errors?

Accidental errors are those which remain after mistakes and

systematic errors have been eliminated and are caused by a combination of

reasons beyond the ability of the observer to control. They tend sometimes

in one direction and some times in the other, (i.e.) they are equally likely to

make the apparent result too large or too small.

2. What is well conditioned triangle?

The triangles having internal angles between 30o & 130o are known as

well conditioned triangle. In other words, the shape of the triangle should be

such that any error in the measurement of angle shall have a minimum effect

upon the lengths of the calculated side. Such a triangle is then called well -

conditioned triangle.

3. Define photogram metric.

Photogram metric surveying or Photogrammetry is the science and art

of obtaining accurate measurements by use of photographs, for various

purposes such as the construction of planimetric and topographic maps,

classification of soils, interpretation of geology, acquisition of military

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intelligence and the preparation of composite pictures of the ground. The

photographs are taken either from the air or from station on the ground.

4. What is meant by method of equal shifts?

The method of equal shifts indicates that any shift which is necessary

to satisfy the local equation should be the same for each triangle of the

polygon. Similarly, any shift necessary to satisfy the side equation should

be the same for each triangle.

5. What is the use of correlates?

Correlation is a statistic that measures the linear relationship between

two variables. This explanation is intended to help the layperson understand

the basic concept of correlation without requiring a lot of technical

knowledge. We use correlation to help understand what drives employee

satisfaction or employee engagement within organizations. The same

technique can also be used for customer satisfaction or other types of

surveys as well.

6. Define normal equations.

A normal equation is the one which is formed by multiplying each

equation by the coefficient of the unknown whose normal equation is to be

found and by adding the equation thus formed. As the number of normal

equations is the same as the number of unknowns, the most probable values

of the unknown can be found from these equations.

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7. What are the triangulation adjustments?

Single angle adjustment

Station adjustment

Figure adjustment

8. Define Residual error.

A residual error is the difference between the most probable value of a

quantity and its observed value.

Residual error = Most probable value – Observed value

9. Write the types of error measurements.

Mistakes or Gross error

Systematic or Cumulative error

Accidental or Random error

10. What are systematic errors?

A systematic error is an error that under the same conditions will

always be of the same size and sign. A systematic error always follows

some definite mathematical or physical law, and a correction can be

determined and applied. Such errors are of constant character and are

regarded as positive or negative according as they make the result too great

or too small. Their effect is therefore, cumulative.

11. What is the principle of least square?

According to the principle of least square, the most probable value of

an observed quantity available from a given set of observations is the one for

which the sum of the squares of errors is a minimum.

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12. Define most probable value.

The most probable value of a quantity is the one which has more

chances of being true than has any other. It is deduced from the several

measurements on which it is based.

13. What are Mistakes or Gross errors?

Depends upon the observer, a mistake cannot be corrected unless the

observer get training. The mistakes are errors that arise from inattention,

inexperience, carelessness and poor judgment of confusion in the mind of

the observer.

14. Distinguish between true value and most probable value.

S.NO TRUE VALUE MOST PROBABLE VALUE

1. The true value of a quantity is

the value which is absolutely

free from all the errors.

The most probable value of a

quantity is the one which has

more chances of being true than

has any other.

2. The true value of a quantity is

indeterminate since the true

error is never known.

It is deduced from the several

measurements on which it is

based.

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UNIT – IV

1. What are the uses of Tellurometer?

The instrument is highly portable.

Observations can be taken both during day as well as night, while in

the geodimeter; observations are normally restricted in the night.

2. List out apparatus for making sounding.

Sounding boat

Sounding rods or poles

Lead lines

Sounding machine

Fathometer

3. What is the use of Electromagnetic Distance Measurement?

The term EDM is used to describe a category of instruments that

measure distance using an electronic signal. The instrument broadcasts a

focused signal that is returned by a prism or reflection from the object.

4. What do you meant by carrier wave?

A carrier signal, carrier wave or just carrier is the electromagnetic

wave that can be modulated, as in frequency, amplitude or phase, to transmit

speech, music, images or other signals. A wave form (usually sinusoidal)

that is modulated (modified) with an input signal for the purpose of

conveying information. This carrier wave is usually a much higher

frequency than the input signal. The purpose of the carrier wave is usually

either to transmit the information through space as an electromagnetic wave

(as in radio communication), or to allow several carriers at different

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frequencies to share a common physical transmission medium by frequency

division multiplexing.

5. Write the uses of electro optical instruments.

Electro-optical EDMs use the velocity of light waves to determine

the distance between two points. Electro-optical systems are available for a

wide range of applications including night vision systems, medical & laser

surgical instruments, industrial lasers for marking, cutting & welding,

optical information storage systems, imaging systems for satellites, camera,

telescopes & microscopes, laser imaging systems & laser range-finding &

target designator systems for the military.

6. Define electromagnetic waves.

Electromagnetic waves are waves that contain an electric field and a

magnetic field and carry energy. They travel at the speed of light.

Electromagnetic waves, though extremely complex in nature, can be

represented in the form of periodic sinusoidal waves.

7. What are the sources of error?

The errors may be classified as,

Instrumental errors

Personal errors

Errors due to natural causes

8. Define control segments.

Control segment is the vital link in GPS technology. The Control

Segment consists of facilities required for satellite health monitoring,

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telemetry, tracking, command and control, ephemeris computations and up

linking. Control segment functions, providing command and control of the

GPS constellation.

UNIT – V

1. What are the advantages of fathometer?

It is more sensitive than the lead line

The speed of sounding and plotting is increased

It can be used when a strong current is running and when the weather

is unsuitable for the soundings to be taken with the lead line

A record of the depth is plotted immediately and provides a

continuous record of the bottom as the vessel moves forward

The error due to estimation of water level in a choppy sea is reduced

owing to the instability of the boat

2. Define the term remote sensing.

Remote sensing is broadly defined as science and art of collecting

information about objects, area or phenomena from distance without being

in physical contact with them.

3. What are the basic principles of remote sensing?

Every object on the earth emits its own internal energy according to

its molecular and atomic structure, in addition to reflecting sun light during

the day time. The radiations can be registered by sensors in several

wavelengths, including those in the infrared and microwave regions of the

spectrum. When such sensors are installed on aircrafts or on satellites they

can record the earth’s objects from for off distances. Such distant

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acquisition of information about the objects on the earth’s surface is known

as remote sensing.

4. List the types of EDM instruments.

Microwave instruments

Visible light instruments

Infrared instruments

5. What are the applications of fathometer?

It is used for ocean sounding where the depth of water is too much,

and to make a continuous and accurate record of the depth of water

below the boat or ship at which it is installed.

It is adjusted to read depth in accordance with the velocity of sound in

the type of water in which it is being used.

6. Define GPS?

The Global Positioning System (GPS) is a space-based satellite

navigation system that provides location and time information in all weather

conditions, anywhere on or near the earth where there is an unobstructed line

of sight to four or more GPS satellites.

7. Define GIS?

The modern computers can process maps and data with suitable

computer programmer. The process of integrating and analyzing various

types of data with the help of computer is known as Geographic Information

System.

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8. Define spatial data and non – spatial data.

SPATIAL DATA: Any data which are directly or indirectly referenced to a

location on the surface of the earth are spatial data. Also known as

geospatial data or geographic information it is the data or information that

identifies the geographic location of features and boundaries on Earth, such

as natural or constructed features, oceans, and more. Spatial data is usually

stored as coordinates and topology, and is data that can be mapped.

NON-SPATIAL DATA: Data that relate to specific precisely defined

location. The data are often statistical but may be text, images or

multimedia. These are linked in the GIS to spatial data that defines the

location.

9. What are the uses of Total station?

Angle measurement

Distance measurement

Coordinate measurement

Data processing

Mechanical and Electrical Construction

Mining

10. What are the characteristics of different platforms?

Platforms refer to the structures or vehicles on which remote sensing

instruments are mounted. The platform on which a particular sensor is

housed determines a number of attributes, which may dictate the use of

particular sensors. These attributes include: distance the sensor is from the

object of interest, periodicity of image acquisition, timing of image

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acquisition, and location and extent of coverage. There are three broad

categories of remote sensing platforms: ground based, airborne, and satellite.

11. What are the basic principles of data processing?

It is the activity to convert data in to information. The three activities

in data processing are capturing data (Input), manipulating data (Process)

and outputting the result (Output). It is classified in to two, Manual Data

Processing (MDP) and Electronic Data Processing (EDP).

surveying 2

Engineering