surveying bec102 4 - longitudinal and cross sections

8/13/2019 Surveying BEC102 4 - Longitudinal and Cross Sections

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Longitudinal and CrossLongitudinal and Cross

SectionsSections

Sr SITI NUR ALIAA ROSLANSr SITI NUR ALIAA ROSLAN

KLIUCKLIUC


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Outline of LectureOutline of Lecture

IntroductionIntroduction

DefinitionsDefinitions

MethodologyMethodology CalculationCalculation

Output / ProductsOutput / Products

ApplicationsApplications


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IntroductionIntroduction

Two other major uses of levelling are:Two other major uses of levelling are:

Longitudinal sectionsLongitudinal sections CrossCross--sectionssections


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DefinitionDefinition

Longitudinal sectionsLongitudinal sections

The existing ground profile along aThe existing ground profile along a

particular line (normally the centre line ofparticular line (normally the centre line ofexisting proposed work)existing proposed work)

Centre line of railway, road, canal etcCentre line of railway, road, canal etc

Staff reading to 0.01m is adequateStaff reading to 0.01m is adequate


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DefinitionDefinition

CrossCross--sectionssections

Are lines of levels or short profilesAre lines of levels or short profiles

perpendicular to the centre line of a projectperpendicular to the centre line of a project Provide info needed for estimating theProvide info needed for estimating the

quantities of earthworkquantities of earthwork


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MethodologyMethodology

The process of determining a series ofThe process of determining a series of

elevations along a fixed line is referred toelevations along a fixed line is referred to

as Profile Levellingas Profile Levelling Data are taken at regular intervals afterData are taken at regular intervals after

the setting out of Centre Line (CL)the setting out of Centre Line (CL)


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The levels for the defining of the sectionsThe levels for the defining of the sections

may be obtained by one of the followingmay be obtained by one of the following

methods:methods: Conventional levellingConventional levelling

Tacheometric methodsTacheometric methods

Interpretation from digital terrain modelsInterpretation from digital terrain models


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The fixed direction is usually ofThe fixed direction is usually of

significance such as the centreline of asignificance such as the centreline of a

road or riverroad or river

Cross section may be taken at rightCross section may be taken at right

angles to this direction at a constantangles to this direction at a constant

intervalintervalAlong the cross section levels areAlong the cross section levels are

measured at points, usually separated bymeasured at points, usually separated by

a fixed distancea fixed distance


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Similar to the usual process of levellingSimilar to the usual process of levelling

except that more readings to theexcept that more readings to the

Intermediate Sight (IS)Intermediate Sight (IS)

In order to get more info about the landIn order to get more info about the land

profileprofile

BSA

ISPISQ FS1

A

P

Q

1


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Output / ProductsOutput / Products

Longitudinal section planLongitudinal section plan

Cross section planCross section plan


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Horizontal/vertical scaleHorizontal/vertical scale

It is common to use a vertical scale largerIt is common to use a vertical scale larger

than the horizontal one (usually 10:1) inthan the horizontal one (usually 10:1) in

order to make the elevetion differencesorder to make the elevetion differencesclearclear

For eg: Horizontal scale = 1:20For eg: Horizontal scale = 1:20

Vertical scale = 1:20Vertical scale = 1:20


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CrossCross--section plansection plan

Uniform slope 3 readings sufficient

Some changes in slope e.g. 5 readings

Significant changes in slope e.g. 9 readings


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The typical cross sectionsThe typical cross sections

EXISTING GROUND PROFILE

FORMATION LEVEL

WATER LEVEL


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CalculationsCalculations

Construction levelling: often involves relativelyConstruction levelling: often involves relatively

short distances yet a large number (short distances yet a large number (nn) of) of

instrument stationsinstrument stations In this case, an alternative criterion for E canIn this case, an alternative criterion for E can

be used:be used:

Max. acceptable misclosureMax. acceptable misclosure EE (in(in mmmm):):

E =E = D D nn mmmm

5mm & 8mm: commonly adopted values for D5mm & 8mm: commonly adopted values for D


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Plotting the plansPlotting the plans

-- Longitudinal sectionLongitudinal section Define the horizontal and vertical scale (e.g. vertDefine the horizontal and vertical scale (e.g. vert 1:20 ; horz1:20 ; horz 1:500)1:500)

Can use the engine ering ruler to do the plottingCan use the engine ering ruler to do the plotting

40.

858

40.

998

0.

00

40.

773

40.

758

40.

902

40.

907

41.

001

10.

00

20.

00

30.

00

40.

00

50.

00

60.

00

Ground Level (m)

Chainage (m)

Datum = 40.000m

RL of CLs


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Plotting the plansPlotting the plans

-- Cross sectionCross section Define the horizontal and vertical scale (e.g. vertDefine the horizontal and vertical scale (e.g. vert 1:20 ; horz1:20 ; horz 1:20)1:20)

To highlight both componentsTo highlight both components


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Exercise:Exercise:

Draw both the longitudinal and crossDraw both the longitudinal and cross--

section plans in accordance to exact scalesection plans in accordance to exact scale

Use the data provided in the lecture slideUse the data provided in the lecture slide


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Advanced source of dataAdvanced source of data

LIDAR (Light Detection and Ranging)LIDAR (Light Detection and Ranging)

It is rapidly emerging technology for determiningIt is rapidly emerging technology for determining

the shape of the ground surface plus natural andthe shape of the ground surface plus natural and

manman--made featuresmade features

LIDAR is combined with Geographic InformationLIDAR is combined with Geographic Information

System (GIS) data and other surveyingSystem (GIS) data and other surveying

information to generate complex datainformation to generate complex data


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Application of Long and CrossApplication of Long and Cross--

sectionssections In the construction and design of roads,In the construction and design of roads,

highways, railways, pipelines and drainagehighways, railways, pipelines and drainage

systemssystems

Earthwork operationsEarthwork operations

Cut and fill volume calculationsCut and fill volume calculations


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Height of Collimation MethodHeight of Collimation Method

An alternative to the Rise and Fall methodAn alternative to the Rise and Fall method

Normally used when a large number ifNormally used when a large number if

Intermediate Sights are observedIntermediate Sights are observed The height of the telescope axis or heightThe height of the telescope axis or height

of collimation (HC) is measuredof collimation (HC) is measured


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ExampleExample

BSBS ISIS FSFS HCHC RLRL RemarksRemarks

2.0272.027 73.105 + 2.02773.105 + 2.027

= 75.132= 75.132

73.10573.105 BH1BH1

(73.105m)(73.105m)

2.1092.109 75.13275.132 75.13275.132 2.109 =2.109 =

73.02373.023

2.5432.543 75.13275.132 75.13275.132 2.543 =2.543 =

72.58972.589

4.6814.681 75.13275.132 75.13275.132 4.681 =4.681 =

70.45170.451


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Example (Contd)Example (Contd)

BSBS ISIS FSFS HCHC RLRL RemarksRemarks

2.1332.133 4.4274.427 70.705 + 2.13370.705 + 2.133

= 72.838= 72.838

70.45170.451 (4.681(4.681--

4.427) = 70.7054.427) = 70.705

D (CP)D (CP)

3.2463.246 72.83872.838 72.83872.838 3.246 =3.246 =

69.59269.592

EE

1.9571.957 72.83872.838 72.83872.838 1.957 =1.957 =

70.88170.881

FF

3.1593.159 0.6810.681 72.157 + 3.15972.157 + 3.159

= 75.316= 75.316

72.15772.157 G (CP)G (CP)

2.9882.988 75.31675.316 75.31675.316 2.988 =2.988 =

72.32872.328

BH2BH2

(72.328m)(72.328m)


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Arithmetic checksArithmetic checks

Sum of BSSum of BS FS = Last RLFS = Last RL First RLFirst RL

Sum RLsSum RLs First RL = [Sum (HCFirst RL = [Sum (HCii) x n) x nii]]

Sum ISSum IS Sum FSSum FS

Where: HCWhere: HCii is theis the ii th height of collimation and nth height of collimation and nii is the no. of timesis the no. of times

thethe ii th height of collimation was used to compute RLsth height of collimation was used to compute RLs


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Applications of HC methodApplications of HC method

Longitudinal and CrossLongitudinal and Cross--sectionssections

Contouring using grid and levellingContouring using grid and levelling

In general, it is applied when large no. ofIn general, it is applied when large no. of

IS are takenIS are taken e.g. in Earthwork levellinge.g. in Earthwork levelling


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Contouring byContouring by

Grid and LevellingGrid and Levelling


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ContourContour

A contour is a line drawn on a plan joining allA contour is a line drawn on a plan joining all

points of the same height above or below apoints of the same height above or below a

datumdatum

Contours cannot cross, split or join otherContours cannot cross, split or join othercontours, except in the case of an overhang.contours, except in the case of an overhang.

e.g. a cliffe.g. a cliff

The height between successive contours isThe height between successive contours is

called the vertical interval or the contour intervalcalled the vertical interval or the contour interval


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ContourContour

Contour interval value depends on the variation in heightContour interval value depends on the variation in heightof the area being contouredof the area being contoured

-- the contour interval is kept constant for a plan or mapthe contour interval is kept constant for a plan or map

The plan spacing between contour line indicates theThe plan spacing between contour line indicates thesteepness of slopessteepness of slopes

-- Closely spaced lines indicates a steep gradientClosely spaced lines indicates a steep gradient

-- Widely spaced lines indicate a flatter gradientWidely spaced lines indicate a flatter gradient


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ExampleExample

5

5

10

10

15

25

20

15 2025


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Productions of contoursProductions of contours

Direct methodDirect method

Finding points on the ground with the value ofFinding points on the ground with the value of

the required contourthe required contour

Indirect methodIndirect method

Random spot heightsRandom spot heights

Grid of spot heightsGrid of spot heights


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Productions of contoursProductions of contours

(indirect method)(indirect method)

From random spot heights

From a grid of spot heights


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For next practicalFor next practical

Determine the crossDetermine the cross--section and longsection and long--

section for a road, with distance of 100msection for a road, with distance of 100m

Contouring using the Grid and LevellingContouring using the Grid and Levellingmethodmethod

Use the rise/fall or HC method for dataUse the rise/fall or HC method for data

calculationcalculation

surveying bec102 4 - longitudinal and cross sections

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