lecture 6: tacheometry & contents detail...

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Basic Surveying for Engineers: Detail SurveysC. Roberts, L. Ge, School of Surveying and SIS, UNSW, Bruce Harvey (c)

Lecture 6: Tacheometry & Detail Surveys

Field proceduresElectronic data recordingComputer plottingChap. 9 (Uren & Price)

UNSW

Contents

'Breaking down' controlPlotting and scalesOlder mapping methodsModern 'field-to-finish' electronic surveysCase study

Detail Surveys: Some Comments

Heirarchy of control networks - - details surveys are 'connected' to control (providing starting coordinates).Detail surveys are used for many purposes.Detail surveys provide data for project design - -electronic data recording, input to CAD packages.Details surveys carried out at appropriate (plot) scale - -not 'general purpose'.Details surveys nowadays synonymous with "tacheometry".

Plotting

Plans have limited accuracy!!

Accuracy about 1/2 of line thickness+ drawing error ± 0.2 - 0.3 mm

At 1:1000 0.3mm is 30cm

Q: What scales are street directories ?


Plan and Map Scales

Suburban cadastralEngineering constructionStreet directoryTopographic, bushwalkingRegionalAtlas

Typical values1:2001:5001:20,0001:25,0001:100,0001:1,000,000

Plane Table Mapping

A B

Drawing Board

Plane Table and accessories

PlumbLine

Alidade

222

'Chain' Surveys - Tape Only

4.81

14.67

Shed

Grass

7.46

0.71

4.222.00

3.730.60

2.41

0.48

Trees and shrubs

Grass Patio

Patio

-16.15-

-7.47-

-7.15-

House


Optical Distance Measurement

Stadia Tacheometry:no electronicsslower and less accurate than electronic tacheometers

See Lecture 3 on Distances + text book

Theodolite + Tape Survey

G I ShedSilky Oak0.3d 10s

Gum0.2d 4sTea tree

0.1d 3sPalm0.2d 4s

W.C.

Brick & G.I. Roof

Conc.D’way

Conc.Driveway

QUEEN MARY ST

150 Conc K & GELP

PMG

Old P

aling0.23 w

ide

New Paling Lapped & Capped

KIN

GG

EOR

GE

SR

OA

D

ELP

Conc. B

lk Ret w

all

Post & rail

Bk. Fence 1.8 high

SV ELP

ELP

ELP ELP


Gum0.2d 4sTea tree

0.1d 3sPalm0.2d 4s

W.C.

Brick & G.I. Roof

Conc.D’way

Conc.Driveway

QUEEN MARY ST

150 Conc K & GELP

PMG

Old P

aling0.23 w

ide


KING

GEO

RG

ES

RO

AD

ELP

Conc. B

lk Ret w

all

Post & rail

Bk. Fence 1.8 high

SV ELP

ELP

ELP ELP



Gum0.2d 4sTea tree

0.1d 3sPalm0.2d 4s

W.C.

Brick & G.I. Roof

Conc.D’way

Conc.Driveway

QUEEN MARY ST

150 Conc K & G

ELPPMG

Old P

aling0.23 w

ide


KIN

GG

EO

RG

ESR

OAD

ELP

Conc. B

lk Ret w

all

Post & rail

Bk. Fence 1.8 high

SV ELP

ELP

ELP ELP



Electronic Distance Measurement

INFRARED instruments, use prisms as reflectors, limited range (<5km), light and integrated within theodolite ("total station").LASER instruments, long range (30-60km), high accuracy.MICROWAVE instruments, very long range (up to 100km), not common for engineering applications.

333

B

A

DV Ht

Hi

Horiz Dis

∆h

RLB = RLA + h

= RLA + Hi + v - Ht

∆

Theodolite + Distance


EDM Tacheometry

Electronic tacheometers sometimes also called "total stations".Traversing, set- outs and detail surveys can be carried out rapidly.Electronic measurement of angle and distance, and data recording - - "field to finish" surveying.Feature coding using keyboard, barcodes, etc.Large variety of computer software for plan preparation.


Principles of Tacheometric Surveys

Large-scale plans -- "detail surveys" Product is a planimetric or contour plan showing man-made and natural details.Many plans are now computer generated.Set-up instrument at point of known position and height.'Radiate' points of detail.


Principles ...

Use check measurements.Calculate coordinates and height.Be aware of scale of finished plan:– (1:100 implies 1mm on plan is 0.1m on ground)

Spacing of natural surface points must reflect scale of plan and nature of terrain.


Principles ...

May use grid, but prefer to locate change of ground slope.Contouring can be done automatically by plotting software.Survey trees (note trunk & crown diameters, variety, etc.).Detailed description of object. Pick up enough points to define curves.Pick up top and bottom of kerbs (for height difference, not plot).Particular attention around buildings (remember there are usually right-angled corners!).Always check for blunders, bumped instrument, etc.Better to have too many points than too few!

Computer Contouring

60

62

64

66

6858

56

54

5259.1 60.9

65.2

57.1

56.5 62.5

66.6

68.558.2

59.7 62.3

64.4

66.0

67.466.265.163.1

62.3 62.8

59.7

53.6

444

If you want heights or contours, measure height of instrument!

FL & FR Theodolite Measurements?

2 faces requires repeat obs, mean reduces random errors, differences detect gross errors.2 faces reduce systematic errors: axis tilt, collimation error, etc.2 faces does not reduce vertical axis (levelling) tilt or centring errorTraverse / control = 2 faces, Radiation = 1 face1 face obs faster & plotting requires low precision.

Electronic Data Recording

1. Measure and record data

2. Down load data into computer

3. Process and plot plans


Field Coding

Record measurements:e.g. point ID, direction, ZA, slope distanceRecord codes or comments:e.g. date, height of target, coordinates,

feature ID / codes, etc.

555



Feature Codes

Entity & strings, e.g. 40902 409 = top of kerb,

02 = join kerb points togethere.g. 00100203

001 = permanent survey mark00 = individual point, not a string

203 = point number / ID

100m

Detail Survey - Case Study

St John’s College, MorpethJuly 1998

Survey: G. Donovan, C. Reid, T. Rofe

Civilcad & Calcs: C. ReidPowerPoint: B.Harvey


Control Traverse


Control Traverse by another group Basic Surveying for Engineers: Detail Surveys

C. Roberts, L. Ge, School of Surveying and SIS, UNSW, Bruce Harvey (c)

Control Traverse by another group

666


Triangular mesh


LEGEND

CLIENT: Mr.S.Ganeshan

SURVEYOR: Cameron.E.Reid,2174004

DATE: 22/08/98

LOCALITY: Morpeth

LGA: Maitland

SCALE 1:500DETAIL AND LEVEL SURVEY

AREA: Section 3 No:2 ,Closebourne Convention Centre.

SUBJECT: GMAT6052 Filed Projects 2

REFERENCE NUMBER: 980001

357800

357800

357900

357900

358000

358000

358100

358100

13769001376900

1377000 1377000

1377100 1377100

VEGETABLE

GARDEN

CARPARK

TENNIS

COURT

GREEN

STAND OF

TREES

BRICK

BUILDING

PLAYGROUND

GAS TANK

FIBRO

BUILD

SA NDSTO N

E

BUIL DI

N G

GRAV E

L

ROAD

BITUMEN

ROAD

BRICK BUILDING

(TILE ROOF)

BRICK

BLD

(TILE ROOF)

BITUMEN

ROAD

BRICK

BUILDI

NG

SANDSTONE

BUILDING

OLDSTONE

BLD

PRIVATE

PROPERTY

LAUNDRY

HOUSE

(TIMBER

AND ALUMUNIUM)

PP

PP

PP

LP

SUNDIAL 912

906

913

902916

917

914

915

901

911

910

PP

LP

GIP

GIP

FOOTPATH

FOOTPATH

STAND

OF TREES

35

35

35 35

35

35

35

35

35

35

35

35

35

35

35

FENCE

CLOTHES LINE

SEWERAGE PIT

NORTH

STATION

VERANDAH

POWER POLEPP

UNDERGROUND

WATER TANK

CONTOUR INTERVAL: 0.5m

RETAINING

WALL

NATURAL SURFACE

Final computer generated plan

LEGEND

CLIENT: Mr.S.Ganeshan

SURVEYOR: Cameron.E.Reid,2174004

DATE: 22/08/98

LOCALITY: Morpeth

LGA: Maitland

SCALE 1:500DETAIL AND LEVEL SURVEY

AREA: Section 3 No:2 ,Closebourne Convention Centre.

SUBJECT: GMAT6052 Filed Projects 2

REFERENCE NUMBER: 980001

357800

357800

357900

357900

358000

358000

358100

358100

13769001376900

1377000 1377000

1377100 1377100

VEGETABLE

GARDEN

CARPARK

TENNIS

COURT

GREEN

STAND OF

TREES

BRICK

BUILDING

PLAYGROUND

GAS TANK

FIBRO

BUILD

SA NDSTO N

E

BUIL DI

N G

GRAV E

L

ROAD

BITUMEN

ROAD

BRICK BUILDING

(TILE ROOF)

BRICK

BLD

(TILE ROOF)

BITUMEN

ROAD

BRICK

BUILDI

NG

SANDSTONE

BUILDING

OLDSTONE

BLD

PRIVATE

PROPERTY

LAUNDRY

HOUSE

(TIMBER

AND ALUMUNIUM)

PP

PP

PP

LP

SUNDIAL 912

906

913

902916

917

914

915

901

911

910

PP

LP

GIP

GIP

FOOTPATH

FOOTPATH

STAND

OF TREES

35

35

35 35

35

35

35

35

35

35

35

35

35

35

35

FENCE

CLOTHES LINE

SEWERAGE PIT

NORTH

STATION

VERANDAH

POWER POLEPP

UNDERGROUND

WATER TANK

CONTOUR INTERVAL: 0.5m

RETAINING

WALL

NATURAL SURFACE

Final computer generated plan

TENNISCOURT

STAND OFTREES

BRICK BUILDING

PLAYGROUND

SAN

DSTO

NE

BU

ILDIN

G

GR

AVELRO

AD

BRIC

K BU

ILDI

NG

(TIL

E RO

OF)

BRICKBLD

(TILE ROOF)

BRICK

BUILDING

SANDSTONE

BUILDING

PP

LP

SUNDIAL 912

913

914

PP

LP

GIP

FOOTPATH

FOOTPATH

STAN

DO

F TR

EES

35

35


Large Scale Mapping: Comments

Large amount of digital data already available in GIS databases -- utilities, cadastral boundaries, etc.Low-level aerial photography can be used -- scanned and digitally converted to DTMs, etc.Metre-level satellite imagery/photography available.Future map 'products' will be result of data fusion from different sources, then 'draped', warped and viewed as 'fly-throughs' or VR landscapes.

Latest Developments

Robotic instruments.GPS, laser scanners, etc.Field computer screen plots.More complex, & realistic visualisations.

777


Real-time Kinematic (RTK) GPS for detail surveys

• Requires 2 GPS receivers and a radio link for real-time differential positioning

• cm-level accuracy

• High productivity

• Not good under thick tree cover

• Compatible with most CAD softwares


Photogrammetry

A plane equipped with a high resolution camera takes overlapping aerial photographs of the terrain.Adjacent pairs of photographs are oriented to replicate the aircraft position at time of exposureStereo images can be used to generate contours and detailTraditional method of map making – still in use although becoming more digital and automated

Courtesy http://www.crssa.rutgers.edu/courses/airphoto/airphoto7

Airborne laser scanning

Laser scanner is mounted in an aircraft and emits a laser beam which is reflected off the ground surfaceElevation of scanned surface can be determined by signal time-of-flightRequires accurate information of orientation and position of aircraft during flight

Courtesy AAM Surveys

3D laser scanning

Tripod mounted device, measures flight time of emitted radiation to produce a “point cloud” of 1000s of points. Data can be edited to produce 3D mapsUseful for structural monitoring and high definition surveying


Summary

Traverse technique to 'bring in control'.Points or features of interest can be 'picked up' by radiating them using a tacheometer.Electronic measurement of angles & distance, and data recording (inc. attributes) -- "field to finish" surveying.Real-time high precision GPS techniques are increasingly used.'Measuring up' using tapes & offset techniques useful.Latest developments more suited to larger jobs requiring high productivity.

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