Lec Intro Construction Surveying I PDF

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Course Description- Applications- Taping Errors - Electronic Distance Measurement...

Description

Construction Surveying I SUR8411 – Construction Technician - Civil Technology (Academic Level 01)

Course instructor:

Federico Fernández, Ph.D., P.Eng. Email: [email protected] Text Message: (613) 978-1060

Course Description • Textbook Surveying with Construction Applications, Barry Kavanagh and Dianne K. Slattery, 8th Edition, ISBN13: 9780132766982 E-Textbook

• Lectures – – – – –

Room CA122 Review of Concepts Problem Examples Assignments Evaluations

• Fieldwork: – – –

West Entrance ACCE Front Entrance Bldg B Conducted in groups, evaluated individually

Notes: •

The schedule may change as a result of a number of circumstances, including weather.

•

Students are expected to prepare for class sessions by reviewing relevant textbook sections as well as notes, demonstrations and examples posted on Blackboard.

•

The midterm and final exams are “closed book”, allowing only the use of writing instruments and a standard calculator.

Expectations Item

Rationale

Will track Attendance

Participation is Evaluated

Will form Groups (Random)

Fieldwork is done by Surveying Crews

Will track Equipment (Sign in / out)

Assigned by Group Number

Will keep CA122 locked when all Groups are out during Fieldwork

To maintain a secure learning environment

No food or disruptive activities in class

To maintain a good learning environment

Will follow safe procedures

To maintain a safe learning environment

Text or Call (613) 978-1060 for Assistance

To remain accessible to all 6 groups

Agreed

√ √ √ √ √ √ √

My School Hours:

Consultation Options: E-mail: [email protected] Text Message: (613) 978-1060 In Person: Please make appointment by E-mail or Text

Brief Outline of SUR8411 • • • • • •

Distance Measurements Leveling Field Notes Angle Measurements Traverses Intro to Total Station

Distance Measurement • Various methods for making linear measurements: – – – – – – – – –

pacing chaining odometer optical rangefinders tacheometry (stadia) subtense bar taping electronic distance measurement (EDM) GPS, etc

• Pacing –

can provide sufficient accuracy for some applications (geology, forestry, etc.)

–

can be used to check for blunders

• Odometer –

converts to distance the number of turns of a wheel of known circumference

–

can also be used as a rough check for blunders

• Stadia –

quickly determines the horizontal distance and elevation of a point

–

reading the top and bottom cross hairs through a telescope instrument

–

capable of an accuracy of 1 part in 500

Applications Method

Accuracy

Application

Pacing

1/50 to 1/100

Reconnaissance

Odometer

1/200

Reconnaissance

Tacheometry

1/500 to 1/3,000

Reference checking

Taping

1/1,000 to 1/5,000

Land surveys

EDM

Up to 1/300,000

All surveying

Taping Errors

• Sources of Common Mistakes: – – –

Instrumental (e.g. tape kinks) Natural (e.g. rain, wind effects) Personal (e.g. reading posture)

• Systematic Errors: –

Lcorr

=

L+C

Tape Length: the correction (CL) is determined from the actual tape length (l), the tape’s nominal length (l’) and the measured length (L):

CL = L (l - l’) ÷÷ l’ –

Temperature: steel tapes are standardized for T = 20 °C. the correction (CT) is determined from the coefficient of thermal expansion (k), the tape temperature at the time (T1 ) of measurement and the measured length (L):

CT = k (T1 - T) L –

Inconsistent Pull: tapes stretch under tension and the correction (CP) is determined from the cross sectional area (A), modulus of elasticity (E) and pull applied to the tape(P1) relative to the standard pull (P):

CP = (P1 - P) L ÷ (A E) –

Sag Correction: tapes that are not supported along the entire length will sag and the correction (CS) is determined from the tape’s weight (w), the tape’s length (L) and pull applied to the tape (P1): 3

2

CS = - w2 L ÷ (24 P 1 )

Electronic Distance Measurement • Velocity of electromagnetic energy –

Reflector

V = ƒ λ where, ƒ is the frequency in hertz (cycles/second) and λ is the wavelength

• In vacuum, electromagnetic waves move at speed of light (c = 299,792,458 m/sec) –

V = c/n where, n is the refractive index of the medium through which the wave propagates in air, the n value is approximately 1.0003 and ranges from 1.0001 to 1.0005 depending on pressure and temperature

• Process of Electronic Distance Measurement: – –

For a constant speed of V over a straight distance L in a time interval ∆t, then L = V ∆t = (c/n) ∆t But since the speed of light (c) is very high, the time interval ∆t would need to be measured extremely accurately. Instead, the principle of EDM is based on the following relationship:

1

λ

2

λ

4

3

λ

λ

5

λ

6

λ

7

λ λ 2L

2L = (nλ λ + p) 10

9

8

λ

λ

11

λ

12

λ

p

Survey Leveling • Concepts: – –

Determining elevations of points or differences in elevation Many applications in mapping, design and construction: • • • • •

vertical alignment (roads, canals, sewers, etc) layout to planned elevations earthwork quantities (cut/fill volumes) drainage studies and mapping ground subsidence (settlement)

• Basic Methodology: – – – – – –

Sta. BM

Locate Benchmark (BM or TBM) Set-up Level instrument Take Backsight (BS) reading Compute Height of Instrument (HI) Read Foresight (FS) Compute Elevation

B.S. 0.982

H.I.

F.S.

Elev. (m) 87.400

88.382 Elev

1.225

87.157

Backsight

Foresight

Leveling Instruments

Differential Leveling •

Required when the dimensions exceed the reach of the level – –

In this case, over 33 feet difference in elevation which exceeds the length of the rod Could also be required if the horizontal distance is too far for one reliable reading

Sta. BM

B.S. 1.33

TP1

0.22

H.I.

F.S.

Elev. (ft) 2,053.18

8.37

2,046.14

7.91

2,038.45

11.72

2,027.69

8.71

2,019.44

2.61

2,028.78

0.68

2,040.65

0.21

2,053.21

2,054.51 2,046.36 TP2

0.96 2,039.41

TP3

0.46 2,028.15

Oak

11.95 2,031.39

TP4

12.55 2,041.33

TP5

12.77 2,053.42

BM

Field Notes •

Records of work done in the field – – –

•

Only permanent record of fieldwork Subject to court review in litigation cases The information is worth several thousand $$$

Requirements – – – – –

•

Accuracy Integrity Legibility Arrangement Clarity

Notekeeper Recommendations – – – – – – – – –

Sharp pencil 3-H, not soft, not ball pen Erasure is not permitted, strikethrough Avoid crowding, paper is cheap Draw sketches to proportion, not to exact scale Include meridian (North) arrow in all sketches Repeat aloud values for verification Show precision by means of significant figures Make all checks before leaving the field Sign in the lower right-hand corner

•

Field Note Contents – – – – – –

Project Name, location, date and times of fieldwork Weather Conditions Surveyors names and duties Instrument type and number Observations, sketches, descriptions, explanations. Owner’s name, address, phone number in notebook cover with permanent ink

Sample of Leveling Field Notes Note keeper Rod Person Instrument Operator

Closure Check

Arithmetic Check

Signed by Note keeper

Angle Measurements • Various methods for making angle measurements: – Plane table – Sextants – Compass – Tape (or other distance measurement) – Theodolite – Total Station

• Generally define angles by 3 characteristics: –

Starting Line (Backsight)

– Direction of turning (clockwise or counterclockwise) – Angular distance (value)

α

• Units of angle measurement: –

Sexagecimal (Degrees, minutes, seconds or Decimal Degrees) - North America

– Grad - metric (100 grads per quadrant or 400 grads per revolution) - Europe – Radians (2π radians per revolution) - for computations

Components of a Digital Theodolite Objective Lens

Peep (Open) Sight Focus Knob Parallax Adjustment Battery Housing

Optical Plummet

Vertical Fine Motion Adjustment

Vertical Clamp

Fine (tube) Level Vial

Horizontal Clamp

LCD or Digital Display

Leveling Screw

Horizontal Fine Motion Adjustment Coarse Level (Fisheye) Vial

Traverses “OPEN TRAVERSES” Distance and angles measured

P (Np, Ep)

α4 α2 α1

D3

α3

D4

D2

D1

P (Np, Ep)

Na, Ea

D2

α3 D3

α2 D1

Na, Ea

α1

“CLOSED TRAVERSES” α4 Distance and angles measured

D4 D6

α6

D5

α5

Components of a Total Station

Electronic Theodolite + EDM + On-Board Micro-processor + Data Storage

Peep (Open) Sight Objective Lens

Parallax Adjustment Focus Knob Vertical Fine Motion Adjustment

Vertical Clamp

Fine (tube) Level Vial

Horizontal Clamp

Battery Housing

Horizontal Fine Motion Adjustment

Operational Panel

Optical Plummet

External Power Connector LCD Digital Display

Coarse Level (Fisheye) Vial Tribrach Clamp

Data Input/Output Connector Leveling Screw

Fieldwork: Distance and Leveling • Site Reconnaissance: – Walk out the area to identify: • Access conditions (traffic, obstructions, etc.) • Fieldwork hazards (terrain, animals, equipment, weather, etc.) • Personnel Protective Equipment (Vests, signage, etc.)

BM

• Safety First: – – – –

Stay OFF the road Wear Protective Equipment Watch your step (trip/falls) Do not rush!

• Complete the Assignment: – – – –

Review instructions and Examples Plan and do the fieldwork Complete calculations and checks Submit the fieldnotes...