II/IV B.Tech (Regular/supply) Examination (Nov-2016)

First Sem Surveying – I (14CE303) Civil Engineering

(Scheme of Evaluation)

1. Answer all questions [(11 x 1 = 11M )+ (1x2= 2M), Total = 12 M]

a. What is the degree of accuracy in chain surveying?

Ans: Degree of accuracy indicates the accuracy attained in the measurements.

In Chain surveying Degree of accuracy = Probable error/ measured distance

b. Comparison of steel bands with chain.

Ans: Steel bands are provided with a handle at each end, similar to handles of a

measuring chain. The handles are fastened by a metal ring to a small metal loop

riveted to the end of the band.

c. What is the principle of optical square?

Ans: The optical square uses the ‘principle of optics’ or 'laws of reflection of light' as

its basic principle.

And a very simple geodetic instrument that is used to lay off angles that are multiples

of 90° or of 45°. d. Draw the following conventional symbols i) Road & rail level crossing Ii) culvert (2M)

Ans: (i)

ii)

e. Explain qualities of magnetic needle.

Ans: i) A magnet needle attracts magnetic materials towards itself.

ii) A freely suspended bar magnet always aligns in the north-south direction.

iii) A magnetic needle changes its position from time to time.

f. Define magnetic declination.

Ans: The horizontal angle between true meridian and magnetic meridian is known as

magnetic declination.

g. What are agonic lines?

Ans: Lines joining points of zero declinations are called ‘Agonic Lines’.

h. Define change point.

Ans: Is a point to which a foresight and back sight are taken in levelling.

i. Define reversing.

Ans: It is the process of rotating the telescope over the horizontal axis through 180o in

the vertical plane.

j. The contour interval on a map is 10 m. If the upward gradient of 1 in 30 is required

to be drawn between two points, what will be the horizontal equivalent?

Ans: Gradient = contour interval/ Distance

i.e. Horizontal equivalent = 10/1/30 = 300 m

k. Write the details of total length & length of each link for different chain.

Ans: Gunter’s chain length = 66 ft, 1 link = 0.66 ft

Engineer’s chain length = 100 ft, 1 link = 1 ft

Revenue chain length = 33 ft, 1 link = 2 .062 ft

UNIT -I

2. (a) Describe briefly the classification of surveying based on (i) purpose and

(ii) instruments. (6M)

For explaining any three based on purpose (3x1 =3 M)

For explaining any three based on instruments (3x1 =3 M)

Classification of surveying based on purpose:

Control surveying: To establish horizontal and vertical positions of control points.

Land surveying: To determine the boundaries and areas of parcels of land, also known as property survey, boundary survey or cadastral survey.

Topographic survey: To prepare a plan/ map of a region which includes natural as well as and man-made features including elevation.

Engineering survey: To collect requisite data for planning, design and execution of engineering projects. Three broad steps are

Route survey: To plan, design, and laying out of route such as highways, railways, canals, pipelines, and other linear projects.

Construction surveys: Surveys which are required for establishment of points, lines, grades, and for staking out engineering works (after the plans have been prepared and the structural design has been done).

Astronomic surveys: To determine the latitude, longitude (of the observation station) and azimuth (of a line through observation station) from astronomical observation.

Mine surveys: To carry out surveying specific for opencast and underground mining purposes

Military Survey: This survey is meant for working out plans of strategic importance.

Geological Survey: This survey is for finding different strata in the earth’s crust.

Archeological Survey: This survey is for unearthing relics of antiquity.

Classification of surveying based on instruments:

Chain surveying is a type of survey in which the surveyor takes measurements in the field and

then completes plot calculations and other processes in the office. Chain surveying is best used

for smaller planes with few details.

Compass surveying is a type of surveying in which the directions of surveying lines are

determined with a magnetic compass, and the length of the surveying lines are measured with a

tape or chain or laser range finder. The compass is generally used to run a traverse line.

Theodolite surveying used for measuring both horizontal and vertical angles, as used in

triangulation networks, and geo-location work. It is a tool used in the land surveying and

engineering industry, but theodolites have been adapted for other specialized purposes as well.

Plane Table Surveying is a graphical method of survey in which the field observations and

plotting are done simultaneously. • It is simple and cheaper than theodolite survey. It is most

suitable for small scale maps.

Tachometry (from Greek, quick measure), is a system of rapid surveying, by which the positions,

both horizontal and vertical, of points on the earth surface relatively to one another are

determined without using a chain or tape or a separate leveling instrument.

Photogrammetric Surveying specialize in the science of obtaining reliable spatial information

from photographic images. Photogrammetrists analyze aerial and terrestrial photographs to

obtain information about physical objects and the environment.

EDM survey is a survey done on the principle of optics. A total station or TST (total station

theodolite) is an electronic/optical instrument used in modern surveying and building

construction. The total station is an electronic theodolite (transit) integrated with an electronic

distance meter (EDM) to read slope distances from the instrument to a particular point.

2. (b) What are the qualities of a good surveyor? Describe briefly the various duties of a

surveyor. (6M)

For writing any five points in the following qualities (4M)

Qualities:

He should plan his work systematically.

He should work carefully and accurately.

He should record the observations in a neat and orderly fashion.

He should know the relative importance of various measurements and should

develop some sense of proportion as to what is important and what is not.

He should have the essential habit of checking measurements and calculations.

For Just description of the duties as follows (2M)

Filed work: Consists of taking measurements and recording them in a proper field

book

Office work: The office work of a surveyor consists of converting field work, in to

different requirements like computations, drafting and designing.

Care and adjustments of instruments: The surveyor must know how to care and

adjust the instruments, surveying instruments are very delicate. These should be

handled with care so that they are not damaged.

(OR)

3. (a) What do you understand by degree of accuracy? Discuss various methods of

expressing degree of accuracy? (6M)

For definition (1M)

Degree of accuracy:

The degree of accuracy indicates the accuracy attained in the measurements. It is usually

expressed as the ratio of the error to the measured quantity.

For explain the following methods (5M)

1. Linear measurements :

Degree of accuracy = probable error/measured distance

2. Traverse:

Degree of accuracy = Error of closure/Total perimeter of traverse

3. Angular measurements:

For angular measurements, the degree of accuracy is usually expressed as K√𝑁

Where N = number of angles measured

K = Angular error of closure/√𝑁𝑢𝑚𝑏𝑒𝑟𝑜𝑓 𝑎𝑛𝑔𝑙𝑒𝑠 𝑚𝑒𝑠𝑢𝑟𝑒𝑑

4. Levelling:

For angular measurements, the degree of accuracy is usually expressed as K√𝐿

Where L = Length of horizontal route

K = Error of closure in elevation/𝐻𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝑙𝑒𝑛𝑔𝑡𝑕 𝑜𝑓 𝑟𝑜𝑢𝑡𝑒

3. (b) What is the field work involved in chain surveying? Explain briefly. (6M)

For explaining any four heading in the following (4x1.5 =6M)

1. Reconnaissance: Walk over the area to be surveyed and note the general layout, the

position of features and the shape of the area.

2. Choice of Stations: Decide upon the framework to be used and drive in the station pegs

to mark the stations selected.

3. Station Marking: Station marks, where possible should be tied - in to a permanent

objects so that they may be easily replaced if moved or easily found during the survey. In

soft ground wooden pegs may be used while rails may be used on roads or hard surfaces.

4. Witnessing: This consists of making a sketch of the immediate area around the station

showing existing permanent features, the position of the stations and its description and

designation. Measurements are then made from at least three surrounding features to

the station point and recorded on the sketch. The aim of witnessing is to re-locate a

station again at much later date even by others after a long interval.

5. Offsetting: Offsets are usually taken perpendicular to chain lines in order to dodge

obstacles on the chain line.

6. Sketching the layout on the last page of the chain book, together with the date and the

name of the surveyor, the longest line of the survey is usually taken as the base line and is

measured first.

UNIT -II

4. (a) Explain the different methods of chaining on sloping ground. What is hypotensual allowance? (6M)

For explaining direct method (2M)

For explaining indirect methods (4M)

If the ground is uneven or sloping, the horizontal equivalent of the distance is either measured in the filed or it is computed from the slope distance.

There are basically two methods

(1) Direct method (or) Stepping method

(2) Indirect method

Direct method (2M)

Let AB be the length of line to measured on a sloping ground as shown in fig.

The follower holds the tape firmly at A and the leader goes with a convenient length ‘l1’ of tape say 5m, 10 m, and a ranging road in hand

After ranging, the leader holds the chain horizontally.

He may be guided by the follower or others in the party for horizontality of the tape.

After stretching the tape, with the help of plumb bob or by dropping a pebble, the leader transfers the end of the tape to the ground and marks.

The length of the tape selected such that the drop is never more than the eye sight of the leader.

The length ‘l1’ is noted and they move to measure next step length.

The two step lengths need not be the same.

The procedure continues till the total length is measured.

Total H.D b/w A and B is given by D = l1 + l2 + l3 + l4

Indirect method If the slope of the ground is gentle these methods may be employed.

In these methods linear measurements is along the sloping ground and it involves angular

measurements also.

The following three methods are in common use:

Method –I (By measurement of angles) (1M)

In this method, the slope angle is measured with a clinometer or some other instrument.

For measurement of the slope angle (θ), a mark is made on the ranging rod B at the height

of the observer’s eye.

The follower stands at A with the clinometer in his hand and the leader keeps the marked

ranging rod at B.

The follower sights through the clinometer, and measures the angle of slope.

If L is the inclined distance, measured along the slope, from A to B, the H.D is

If the slope is not uniform, it is convenient to divide the distance between A and B into various

reaches of different slopes.

The intermediate points are located where the slope changes.

The H.D ‘D’ in that case is given by

Where L1, L2 etc are the inclined distance and θ1 , θ2 etc are the angles of slopes.

Method -2 (By measurement of elevations) (1M)

In this method using levelling instruments the difference in level ‘h’ between the points is

measured.

After measuring sloping ground length ‘l’ the equivalent horizontal length ‘L’ can be

calculated as

Method- 3 (By hypotensual allowance) (2M)

In this method, a correction is applied in the field at every chain length and at every point where slope changes.

When the chain is stretched on the slope, the arrow is not put at the end of the chain but

is placed in advance of the end, by of an amount which allows for the slope correction.

In the above fig BA′ is one chain length on slope. The arrow is not put at A′ but is put A,

the distance AA′ being of such magnitude that the horizontal equivalent of BA equal to

one chain.

The distance AA′ is called as hypotensual allowance.

Hypotensual allowance = 100 (secθ-1) links (or) 50 θ2 links, where θ is in radians.

If θ is in degrees then hypotensual allowance = 0.015 θ2links.

4. (b) What are different tape corrections? Describe in brief. How would you obtain the combined correction? (6M)

The following corrections are to be applied to the linear measurements with a chain or a tape where such accuracy is required. (i) Standard length correction

(ii) Slope correction

(iii) Temperature correction

(iv) Pull correction

(v) Sag correction

For explain each correction 1M (5x1 = 5M)

Standard length correction: The correction for standardization in taping is similar to that

considered for chaining, and it is given by

Ca = (ι’- ι)

Where ι

ι’ = Actual length of the tape ι = nominal length of the tape

Slope correction: The correction for slope is given by

Cg = - L (1-cosӨ)

Where L= slope distance, Ө = Angle of slope

Temperature Correction : A chain or a tape of nominal length ‘L’ standardized at

temperature To and having cross sectional area A is employed to measured length at

temperature Tm being the coefficient of linear expansion of the material of the chain or tape

per unit rise of temperature ,

Ct =α (Tm-To)

Pull Correction : chain or tape of nominal length ‘L’ having cross sectional area of the link or

that of a tape, as the case may be, equal to A and standardized under a pull Po is employed to

measure a length at a pull P. If Young’s modulus of elasticity of the material is E the extension

of its length is

Cp= (P-Po) L

AE Sag Correction: In case of suspended measurement across a span L the chain or tape sag to

take the form of curve known as catenary. Sag correction is always negative.

Where w = weight of the tape per metre length

W = Total weight of the tape P = pull applied (in N) l1 = The length of tape suspended between two supports l = length of the tape = nl1 (in m) * Combined correction is obtained by adding all the corrections with their signs. (1M)

(OR)

5. (a) Write the differences between prismatic and surveyors compass. (6M)

For writing any six differences of the following (6 x1 =6M)

S.no

Prismatic Compass Surveyors Compass

1 Graduation circle is fixed to broad type needle. Hence, it will not rotate with the line of sight.

Graduation circle is fixed to the box. Hence, it rotates with the line of sight.

2 There is a prism at viewing end. At viewing end there is no prism. There is only a slit.

3 Sighting and reading can be done simultaneously.

Sighting and viewing cannot be done Simultaneously.

4 The magnetic needle do not act as an index.

Magnetic needle acts as index while reading.

5 The graduations are in whole circle

bearing. (0 to 360o)

The graduations are in quadrantal

system. (0 to 90o)

6 Graduations are marked inverted since its reflection is read through prism.

Graduations are marked directly. They are not inverted.

7 The reading is taken through a prism. The reading is taken by directly viewing from top glass.

8 Tripod may or may not be used. It can be held on a stretched hand also.

Tripod is essential for using it.

5. (b) What is local attraction? Explain the methods to correct the bearings for local attraction?

(6M)

For definition (1M)

Local is the attraction is the attraction of magnetic needle to a local magnetic field other

than earth’s magnetic field.

For the following points (2M)

The local magnetic field is caused by iron fences, iron poles, steel bars, vehicles, steel

doors and windows, iron deposits, etc.

Even small items made of iron or steel such as the wrist watch case, pen, belt buckle,

taping arrows and steel tapes cause local attraction. D.C power lines also develop a local

magnetic field.

To detect local attraction, it is essential to take both the fore bearing and back bearing of

each line.

If the fore bearing and back bearing of a line does not differ by 180°, then there is a

possibility of local attraction during the observation of the line.

Otherwise, if the sum of the interior angles of a closed traverse does not provide (2n - 4)

right angles [where n is the number of sides in the traverse], then there is a possibility of

local attraction during the observation of the traverse.

For the following two cases (2x1.5 =3M)

Correction for local attraction

If local attraction is detected in a compass survey observed bearings may be corrected by

any one of the following two methods:

Method I: It may be noted that the included angle is not influenced by local attraction as

both readings are equally affected. Hence, first calculate included angles at each station,

commencing from the unaffected line and using included angles, the corrected bearings of

all lines may be calculated.

Method II: In this method, errors due to local attraction at each of the affected station is

found starting from the bearing of a unaffected local attraction, the bearing of the

successive lines are adjusted.

UNIT -III

6. (a) Can you use a theodolite as levelling instrument? If so how? (6M)

For writing in generally with a meaningful points give the marks (6M)

Yes a theodolite can be used as a levelling instrument because it is also having the

telescope like levelling instrument.

The telescope of theodolite also having three cross hairs like levelling instrument.

The theodolite could be used for leveling provided a number of precautions are

taken as follows

a) The altitude bubble should be centred and the telescope locked with a vertical

angle of exactly 00-00-00,

b) Read the staff

c) Change face and repeat the above steps

d) The mean of the two staff readings will give a reasonable result over short

distances.

Levelling by theodolite must never be regarded as an acceptable alternative to the

surveyor’s level where accuracy is needed.

6. (b) How would you measure a horizontal angle by repetition? What are its advantages?

(6M)

For procedure (5M)

Procedure: Angle AOB is to be measured by repetition process.

Vernier A is set to 0o and vernier B to 180o

The upper clamp is tightly fixed, and the lower one is loosened. By turning the telescope,

the ranging rod at A is perfectly bisected with the help of lower clamp screw and lower

tangent screw. Here the initial reading of the vernier A is 0o.

The upper clamp is loosened and the telescope is turned clockwise to perfectly bisect the

ranging rod at B. The upper clamp is clamped.

Suppose the reading on veriner A is 30o

The lower clamp is loosened and the telescope is turned in anticlockwise to bisect the ranging rod at A. here the initial reading is 30o for the second observation

The lower clamp is tightened. The upper one is loosened and the telescope is turned clockwise to exactly bisect the ranging rod at B. let the reading on vernier A be 60o

The initial reading for third observation is set to 60o . Angle AOB is again measured.

Let the final angle be 90o which is the accumulated angle.

Angle AOB is 30o

The face of the instrument is changed and the previous procedure is followed.

The mean of the two observation gives actual angle AOB

For advantages (1M)

Advantages:

Errors due to eccentricity of verniers and centres are eliminated.

Errors due to inaccurate bisection of the signal are eliminated.

Other errors are also minimized as the sum is divided by the number of repetitions.

(OR) 7. (a) How would you check the accuracy of an open traverse? (6M)

For writing headings 1M

For explaining the following methods 5M

1. Cutoff line method: (1 M)

No direct checks of angular measurement are available. so indirect checks can be

made. As illustrated in the following fig the addition to the observation of bearing of AB

station A, bearing of AD can also measured if possible. Similarly, at D, bearing of DA can

also be measured and check applied. If the two bearings differs by 180o, the work may

be accepted as correct.

A

2. Sighting a prominent object: (1 M)

If there is a prominent object on one side of the traverse, it can be used for checking the accuracy

of an open traverse. Traverse can be checked by determining the coordinates of the prominent

object w.r.to two traverses.

3. Tying to known stations: (1 M)

If points of known positions such as triangulation stations are situated near the site, the

coordinates of the starting station and the last station can be determined by tying in these stations

to the triangular stations. Thus open traverse is converted to a closed traverse.

4. Closing the traverse: (1 M)

The open traverse can be checked by running a separate series of lines from the last

station to the starting station and thus closing the traverse. the checks for the closed

traverse then can then be applied.

5. Astronomical observations: (1 M) The open traverse can also be checked by astronomical observations. The true bearings of

a few lines are determined by astronomical observations. The true bearings of these lines

are also computed from the bearing of the initial line and the observed angles. The

computed true bearings are compared with the observed true bearings to check the

accuracy of the traverse.

7. (b) The measured lengths of the sides of a closed traverse ABCDE run in the counter-

clockwise direction are tabulated below. Calculate the lengths of CD and DE. (6M)

Line Length (m) Bearing

AB 298.7 0o 0′

BC 205.7 N25o12′W

CD ? S 75o 6′W

DE ? S 56o 24′E

EA 213.4 N 35o36′E

Let 𝒍CD and 𝒍DE are the lengths of the lines CD and DE

∑L = 0

298.7 Cos 0o 0′ + 205.7 Cos25o12′– 𝑙CD Cos75o 6′– 𝑙DE Cos 56o 24′+213.4 Cos 35o36′ = 0 (1.5 M)

0.257 𝒍CD + 0.553 𝒍DE = 658.338 --------------- (1) (1 M)

298.7 Sin 0o 0′ – 205.7 Sin 25o12′– 𝑙CD Sin 75o 6′+ 𝑙DE Sin 56o 24′+213.4 Sin 35o36′ = 0 (1.5 M)

-0.966 𝒍CD + 0.832 𝒍DE = -36.638 --------------- (2) (1 M)

By solving equations (1) and (2) we get

𝒍CD = 759. 33 ≈ 760 m (0.5 M)

𝒍DE = 837. 26 ≈ 838 m (0.5 M)

UNIT -IV

8. a) What are different types of errors which can occur in theodolite surveying? How

would you avoid them? (5M)

i) Instrumental Errors (2 M for writing any three)

Non – adjustment of plate bubble: the axis of the plate bubble may not be perpendicular to

vertical axis.

The horizontal circle is inclined and the angles will be measured in all inclined plane

Line of Collimation not being Perpendicular to horizontal axis:

A cone is formed when the telescope is revolved in vertical plane causes an error in

observation; error can be eliminated if angles from the both the faces are taken as the

average reading

Horizontal axis is not being perpendicular to vertical axis

Can be eliminated if angles from the both the faces are taken as the average reading

Line of Collimation not being Parallel to axis of telescope: this error can be eliminated if

reading are taken on both the faces

Eccentricity of the inner and outer axes

Graduation are not uniform

ii) Personal Errors (2 M for writing any four)

The centering may not be done properly

The levelling may not be done properly

If the clamp screw are not properly fixed

Proper tangent screw is not operated

The focusing is not done perfectly

The objects may not be bisected properly

Error in recording the veriner reading because of oversight.

iii) Natural Errors (1 M)

– High temperature cause irregular refraction

– High wind cause vibration of the instrument; wrong readings

8 .b) The following consecutive readings were taken with a 5 m levelling staff on

continuously sloping ground at a common interval of 15m; 0.385, 1.030, 1.925,

2.825, 3.730, 4.685, 0.625, 2.005, 3.110 and 4.485..The reduced level of first point

was 210.125 m. Rule out a page of a level-field book and enters the above readings.

Calculate R.L’s of the points by rise and fall method and also the gradient of the line

joining the first and last point. (7M)

For entering the given data in correct manner – 2M

For calculation of Rise or fall values of all station points – 2M

For calculation of Reduced levels of all station points – 2M

For Arithmetic check – 1M

For calculation of gradient b/w first & last points – 1M

Station B.S I.S F.S Rise Fall R.L Remarks

1 0.385 210.125 First point

2 1.030 0.645 209.480 I.P1

3 1.925 0.895 208.585 I.P2

4 2.825 0.900 207.685 I.P3

5 3.730 0.905 206.780 I.P4

6 0.625 4.685 0.955 205.825 C.P

7 2.005 1.380 204.445 I.P5

8 3.110 1.105 203.340 I.P6

9 4.485 1.375 201.965 Last point

Arithmetic Check:

∑B.S – ∑F.S = ∑Rise – ∑Fall = L.R.L – F.R.L

(1.01) - (9.17) = (0.0) - 8.16) = (201.965)-(210.125)

– 8.16 = – 8.16 = – 8.16

Hence O.K

Gradient b/w first & last points = Elevation diff b/w first & Last point Distance b/w two points

= (201.965 – 210.125) (8 x 15)

= 1 (Falling Gradient) 14.45

(OR)

9. a) What is contour line? What is the importance of contour maps in civil engineering

works? (6M)

Contour line: (For definition 1M)

Is an imaginary line on the ground surface joining the points of equal elevation is known

as contour.

For explain any three uses out the following with sketches (5M)

(1) Determination of the character (or Nature) of the terrain

The most important use of the contour maps is that the character of the terrain can be

determined by its inspection, without going to the site.

The characteristics of the various contours provide sufficient information for a preliminary

design and estimate.

Ex: To visualize the nature of ground along a cross section of interest, a line say XY

is being considered through the contour map (As shown in following fig). The intersection

points between the line and contours are projected at different elevations of the contours

are projected and joined by smooth curve. The smooth curve depicts the nature of the

ground surface along XY.

(2) Selection of a suitable site

The most suitable site for various engineering works, such as a reservoir, canal, sewer,

road or railway may be selected if the contour map of the area is available.

The contour map will help in the preliminary selection.

For the final selection, the detailed survey would be required in most cases.

(3) Determination of sections

If the contour map is available, the section along any line can be determined.

The section obtained is useful for determining the general shape of the ground along a

taken line, and for calculation of earthwork along a route.

(4) Intervisibility between two points

The contour map can be used to determine the intervisibility between two points on the

surface.

(5) Location of a route

A contour map is extremely useful for locating the route of a highway, railway, canal or a

sewer line, at a given gradient. The process is also known as the tracing of contour

gradients.

Suppose if the gradient is 1 in 10 from starting point of R.L of 200, as the contour interval

10m then the required horizontal equivalent required would be 100 m. Draw a arc from

the first point on the contour 210. Similarly repeat the same procedure for all remaining

contours.

(6) Determination of catchment area

The catchment area of a river is determined by using contour map.

The watershed line which indicates the drainage basin of a river passes through the ridges

and saddles of the terrain around the river. Thus, it is always perpendicular to the contour

lines.

The catchment area contained between the watershed line and the river outlet is then

measured with a planimeter.

(7) Estimation of reservoir capacity

The storage capacity of a reservoir is determined from contour map. The contour line

indicating the full reservoir level (F.R.L) is drawn on the contour map.

The area enclosed between successive contours are measured by planimeter.

The volume of water between F.R.L and the river bed is finally estimated by using either

Trapezoidal formula or Prismoidal formula.

Where ‘h’ is the contour interval and ‘n’ is number of segments.

Prismoidal formula is applicable only when ‘n’ is odd. If number of segments are even, (n

is even), for (n -1) segments prismoidal rule may be applied and for the last one

trapezoidal rule is applied.

9. b) Discuss the characteristics of contours. Give the suitable sketches. (6M)

For explaining any six characteristics with suitable figures of the following (6x1 =6M)

All points in a contour line have the same elevation.

Flat ground is indicated where the contours are widely separated and steep- slope where

they run close together.

A uniform slope is indicated when the contour lines are uniformly spaced and

A plane surface when they are straight, parallel and equally spaced.

A series of closed contour lines on the map represent a hill, if the higher values are inside.

A series of closed contour lines on the map indicate a depression if the higher values are

outside (As shown above)

Contour line cross ridge or valley line at right angles. If the higher values are inside the bend

or loop in the contour, it indicates a Ridge.

If the higher values are outside the bend, it represents a Valley

Contour lines cannot merge or cross one another on map except in the case of an overhanging

cliff.

Depressions between summits is called a saddle. It is represented by four sets of contours as shown. It represents a dip in a ridge or the junction of two ridges. And in the case of a mountain range, it takes the form of a pass. ********** THE END***********