Handout 1.pdf

8/22/2019 Handout 1.pdf

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Engineering Graphics & Models

Part 1: Surveying

Part 2: Engineering Graphics & Models

Lecture overview

Part 1: Surveying

Introduction to surveying

Introduction to Height Measurement

Angle & Distance measurement

Detail survey

Lecture overview

Part 2: Engineering Graphics & Models Introduction to Graphics Communication

Sketching

Engineering Geometry

Modeling Fundamentals

Multiviews and visualization

Auxiliary Views

Pictorial projections

Section Views

Dimensioning and Tolerancing

Working Drawings and Assemblies


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Introduction to Surveying

What is surveying?

What do surveyors do?

Why is surveying important?

What is Surveying?

Acquisition, analysis and

presentation of spatial data

Positioning features on and

below the surface of the Earthand representing these

features on a map

Position determined by

measurement of angles,

distances and heights


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What do surveyors do?

Acquirespatial

data using a wide

range of equipmentand techniques

Visualise 2D and

3D data using

AutoCAD, GIS, 3DStudio Max, Maya

etc

Process and analyse

measurements

Total Stations

Taping

Levelling

GPS

Laser Scanning

Coordinate Geometry

Trigonometry

Statistics

GIS

Excel

StarNet

Leica GeoOffice

THE PLOWMAN'SCRAVEN HOUSEFREE

Surveyors in Civil Engineering... Produce accurate, up-to-date plans for the project design process

Map topography to assess the best locations for the construction of tunnels,

bridges, roads etc. (i.e. Detailing)

Set out a site so that structures are built in the correct location and with the

correct building dimensions

Provide stations and benchmarks s to control and monitor the construction

process

Record final as-built positions

Establish control networks for monitoring future movement of structures such as

dams and bridges (deformation monitoring)

Other types of Surveying

Hydrographic Surveying

Photogrammetry

Remote Sensing


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Deformation Monitoring


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What skills does a good surveyor have?

good spatial awareness

trigonometry and coordinate geometrystatistical analysis

computer-aided drawing

project management

using digi tal Geomatics resources

using a wide range of specialist equipment

data acquisition by a range of methods

cartography

Geographic Information Systems (GIS)

www.rics.org

1nd Year Surveying Curriculum

Lecture: Introduction to Surveying & Mapping Science

Lecture: Introduction to Height Measurement Levelling

Lecture: Introduction to Angle and Distance Measurement

Lecture: Detail Survey

Practical: Levelling

Practical: Total Stations

Computer Class: AutoCAD

Computer Class: ArcMap GIS

Map Scales

Ratio of map distance to

ground distance

e.g. 1:10,000 scale implies that 1

unit on the map represents 10,000

units on the ground

The smaller the scale, the

less detail will be shown

small scale > 1:50000medium scale 1:500 to 1:50000

large scale < 1: 500

The smallest distance discernable on a map is 0.2mm (i.e. the thinnest line width

that can be seen by the human eye)

For a 1:500m survey, what level of detail should be recorded?


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Accuracy and Precision

Inaccurate

Precise

Accurate

Imprecise

Accurate

Precise

Types of Error

1. Gross

2. Systematic

3. Random

Plane Surveying

VS

Geodetic Surveying


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Rectangular Coordinate Systems

P

X

Y

x

y

Location of P defined as (x, y)

SOURCE: Bostock and Chandler (1990, p. 75)

Describe the location of London here -

Fundamental Surveying Problem

A

B

N

E

E?

N?


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Trigonometry

A

B

Opposite (b)

Adjacent (c)

sin = opposite/hypotenuse

cos = adjacent/hypotenuse

tan = opposite/adjacent

Polar to Rectangular Conversions

If the coordinates of A (EA, NA) are known, the coordinates of B (EB,

NB) are obtained from A as follows:

EB = EA + EAB= EA + DABsinAB

NB = NA+ NAB = NA + DABcosAB

DAB= the horizontal distance from A to B

AB= the whole circle bearing from A to B

Polar Coordinate Systems

P

rq

N

O

Location of P defined as (r,q)


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SOURCE: Bostock and Chandler (1990, p. 75)

Describe the location of London here -


EB = EA + EAB = EA + DABsinAB


Horizontal Distance

BearingKnown coordinates

BearingsThe bearing () is the direction of a line between two points, measured

as a clockwise angle from Grid North.

2S

1S

q

q

180

N

N


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Polar to Rectangular Conversions: Example

The coordinates of A are 311.617m E, 447.245m N.

Calculate the coordinates of B, where:

DAB = 57.916m and AB = 371120.

SOURCE: UREN & PRICE (2006, p. 189)

Rectangular to Polar Conversions: Example

The coordinates of two points A and B are known as

EA = 469.721m, NA = 338.466m and

EB= 501.035m, NB = 310.617m.

Calculate the horizontal distance DAB and whole-circle bearing

AB of line AB.

Pythagoras Theorem: Distance

The distance formula for Cartesian coordinates is derived from the

Pythagorean theorem. If (x0, y0) and (x1, y1) are points in the plane, then

the distance between them is given by

D = (E2 + N2)

D =1

2


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Quadrants


If the change in E and change in N are both positive, your line

lies in Quadrant I

If the change in E is positive and your change in N is negative

your line lies in Quadrant II

If the change in E and change in N are both negative, your line

lies in Quadrant III

If the change in E is negative and your change in N is positive

your line lies in Quadrant IV

Principle of Radiation

A

r

r = horizontal distance

= horizontal angle subtended from line AB to the detail point

P

(known

coords)

B

(known

coords)

Calculate bearing

from coords of A and B

Calculate bearing

from bearing AB and Hz angle

Calculate coords of P

using bearing and

distance


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Control Points

All survey work is based on a series of control points

Located throughout a site at fixed positions within a

coordinate system

q Starting points for detail survey (topographic mapping) projects

q Dimensional control for setting out

qMeasured repeatedly in deformation monitoring

Final Map

Control Points


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Detail Points

Control Surveys


Baselines, traverses, networks: all require measurement ofangles and distances.

Extended by Intersection and

Resectiontechniques

Definitions of North

Arbitrary North

Common method used on siteto define bearings andcoordinates

Magnetic North

Defined using a prismaticcompass

Grid North

This is the direction defined bythe axes of a coordinate systemand its grid.

True North

Based on the spin-axis of theEarth. Used only in specialconstruction projects.


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Defining a 2D coordinate system

Parameters Position (2), Orientation & Scale

i) define coordinates of one point forposition

ii) define the bearing of one line for orientation

iii) incorporate distances in the survey for scale

(237,155)(237,155)

315

BUILDING 3

BUILDING 1BUILDING 2

1S

4S 3S

2S

Boundary

Establishing control on site

BUILDING 3

BUILDING 1

BUILDING 21S

4S 3S

2S

1000 E

2000 N

Arbitrary Bearing

Arbitrary

Coordinates

Key

____ Measured Horizontal Distances

____ Measured Horizontal AnglesBy traversing

Boundary

[Arbitrary]


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Tying into an existing system

Parameters Position (2), Orientation & Scale

a) start at one known point forposition

b) observe an angle from a 2ndknown point (RO) fororientation

c) incorporate distances in thesurvey for scale

BUILDING 3

BUILDING 1BUILDING 2

1S

4S 3S

2S Boundary

RO

Key

____ Measured Horizontal Distances

____ Measured Horizontal AnglesBy traversing

Known

Coordinates

Known

Coordinates

Tying into existing grid

Determine forward bearings of all the traverse lines

If the internal angles have been measured:

forward bearing = back bearing -clockwise angle (Hz Angle)

If the external angles have been measured:

forward bearing = back bearing + clockwise angle (Hz Angle)

The forward bearings are then used in polar to rectangular

conversions along with the measured horizontal distances to

calculate E and N from one control point to the next


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Bearing is computed using the opening bearing

(either arbitrary or calculated from two known

points) and the horizontal angle measured by

the Total Station


EB = EA + EAB = EA + DABsinAB


Horizontal Distance

measured by total station

Known coordinates

(either arbitrary, existing or

computed)

Intersection

Method of coordinating a point without setting up on it

Establish coordinates for landmarks around a site, e.g. church spires and

tall buildings

Fixing the framework of building structure surveys from ground level

baselines

Used often in setting out, particularly during construction projects with

tall structures

d

gb

A

C

B

D NBC

D EBC

N

D NBC

DEBC

qBC

Elevated point

of unknown coords

Geometry for horizontal observations and computation by

intersection-from-a-baseline

Baseline established from STN A to STN B


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VABC

hi

datum

hB

hC

DhBC

dBC

B

C

hihi

hB

hC

DhBC

HzDistBC

Geometry for vertical observations and computation by

intersection-from-a-baseline

hC=hB +hiB+DhBC

Calculation

Step 1: Calculate the bearing BC

Step 2: Distance BC cannot be measured directly so use the Sine Rule to compute it

Step 3: Calculate the Eand N from B to C

Step 4: Apply Eand N to coordinates of B to c alculate Eastings and Northing of C

Step 5: Calculate the height of Point C use the trigonometric height method, hC= hB +hiB +DhBC

The Sine Rule

^^^

sinsinsin A

BC

B

AC

C

AB==

^

^sin.

sin

A

C

ABBC=


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Intersection: Measurements

To calculate Eastings and Northings of the elevated point, Hz

Angles [b and g] at each station, along the baseline to the elevated

point need to be observed

To calculate the height of the elevated point, the V Angle [V] from

one station to the point needs to be observed

The height of the instrument above the ground mark [h i] must also

be recorded for the trigonometric method for computing height.

Weak observation geometries for intersection-from-

a-baseline

A B

C

A B

C

B

C

qBC

A B

C

A B

C

A B

C

B

C

qBC

Example

The image partwith relationship ID rId2was not found in the file.

A baseline has been established between

Point A and Point B.

A third point, C, is located at the top of anearby church spire.

Calculate the horizontal coordinates and

height of point C.

Instrument height at B = 1.560 m


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Recap

After this introductory lecture you should begin to understand:

Modern definitions of surveying, the importance of surveying and

the role and activities of surveyors within civil engineering

The structure of the surveying curriculum how it relates to the

learning outcomes

The importance of control to all survey projects

How to define a 2D coordinate system

The mathematics behind plane surveying

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