Presented by
Shane MacLaughlin, Atlas Computers Ltd
Dr Paddy Prendergast, DIT
Overview
‘A new specification
designed to address
the demanding needs
of engineering design
in a tightly
constrained urban
environment, in terms
of consistency,
accuracy, re-usability,
and quality’
Background
 QBN Experience pre-2005
 Inconsistent quality of surveys
 Large amount of rework by engineers
 Delivered work not fit for purpose
 Need for improvement
Background
 Surveyors experience
 Weak specification
 Poor statement of requirements
 Falling prices leading to falling quality
 Negative client feedback
Background
 QBN topographic specification
 Developed by Atlas Computers Ltd in conjunction with
Dublin City Council QBN project office
 Rigorously enforced consistency based on use of SCC
software
 Based on IG75 grid
 Presented at Survey Ireland 2007 conference
 Met stated objectives but had shortcomings
Shortcomings in 2007 spec
 Lack of explicit QA/QC procedures
 Lack of illustrative documentation for the contractor
 Based on old IG75 grid rather than new grid
 Based on implicit requirements through provision of
SCC feature library
New specification
 Overcome the shortcomings of the previous
specification
 Generalise the scope to include similar works
 Form a working group representing the interests of all
parties and including the necessary expertise to
represent those interests
Working Group
Working Group
 Peter Muller, QBN Project Office
 Tom Curran, Dublin City Council, Survey and Mapping
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Department
Shane MacLaughlin (Chair) and Áine Martin, Atlas
Computers Ltd
Dr Paddy Prendergast, Irish Institute of Surveyors
Tom Mulreid, Apex Surveys and Society of Chartered
Surveyors
Vincent Molloy, Local Government Computer Services
Board
Ray Murphy and Stan Schoene, Murphy Surveys Ltd
Gerry Healy, RPS Consulting Engineers
Objectives
 Include documented QA/QC procedures to verify the
quality of the delivered product
 Provide consistent results in terms of content,
accuracy, and output
 Move from IG75 to ITM while continuing to support
IG75
 Achievable by the survey contractors
 Cost effective for the client
Components
 Introduction and executive summary
 Specification main body
 Feature library
 User guide
 Sample reports
Quality Assurance
 What is quality?
 ISO 9000 – Say what you do, do what you say, and be able prove it
 ‘conformance to requirements’ – Phillip Crosby
 To create quality we have to understand our requirements. ISO
8402-1986 standard defines quality as "the totality of features and
characteristics of a product or service that bears its ability to satisfy
stated or implied needs.“
 ‘Quality is value to some person or persons’ - Gerald Weinberg
 Quality is subjective and exists within the context of providing value to a given
audience.
 ‘Staying in business’ - W Edwards Deming
 Quality also relates to achieving the requirements with the available resources.
In the context of providing services this amounts to meeting the needs of the
client in a manner that is cost effective to both client and contractor.
 ‘Quality is predictability’ - W Edwards Deming
QA and QC in the specification
 Ensure all client requirements are clearly and unambiguously stated
 Designed such that necessary checks and procedures are included to
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ensure that work being delivered meets stated requirements
Providing visible and meaningful quality checks within all aspects of
the survey
Doing this in such a way that is achievable by the contractor and cost
effective to the client
Recognizing the need for continuous improvement through revisions
to the specification resulting from feedback from all stakeholders
Recognizing the limited scope of this particular specification, and the
need to revisit the requirements to extend its scope
Consistency - Content
 Feature library
 Naming conventions
 Colours, layers, styles
 Annotation
 Significance to the DTM
 Output conventions to
CAD, MX, etc…
 Field implications
 1,2 and 3 point features
 Strings and geometry
Consistency - Accuracy
Manifestation
Missing Node
Two reference points
Pseudo Node
Duplicate Line
Overshoot
Undershoot
Sliver
No reference point
Guptill & Morrison, 1995
Consistency - Accuracy
 Relative & Absolute Accuracy
Recorded Position
333333.333mE, 333333.333mN
RA = 0.34m
RMSE = ?
Building
AA = 0.34m
RMSE = ?
Actual dimension
on Ground = 4.12m
Recorded dimension
in Database = 3.78m
True Position
333333.000mE, 333333.402mN
Boundary Wall
 Relative Accuracy - closeness
between the recorded distance
between two features in a
database and the true distance
 Absolute Accuracy - closeness
of recorded position (coords)
to its true position (Most
Probable Value) – use GPS
Consistency - Accuracy
 Horizontal & Vertical Accuracy - Control
 Absolute - OSi GPS Network - 20mm for horizontal, but
vertical = 2.5 times horizontal (satellite geometry)
 Relative - a few mm possible with vertical (points fixed), but
horizontal ~10mm (due to setting up errors)
 Horizontal & Vertical Accuracy - Topographic detail
 Absolute - width of pogo stick beside wall & trying to hold
pogo vertical rather than centreline ~10cm
 Relative - +/- 10cm at one end and +/-10cm at other end = +/20cm
 Hard & soft surfaces - block wall versus overgrown hedge
with fence (horiz) or paved road versus ploughed field (vert)
Consistency - Accuracy
 Accuracy (repeatability) - daily repeatability test by
University of Melbourne (Gordini et al., 2006) - differences in
metres between ‘true value’ and VRS solutions
Eastings
Northings
Ellipsoidal Heights
• Single shot NRTK observations are not suitable for survey control
• Must be static observations, for a set period & post processed
Consistency - Output
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Cartography
TIN ground model
Sections
Deliverables
 CAD,SCC,MX
 Raw data
 Reports
 Main survey report
 Correction, reduction and
adjustment details
 Station location
 Instrument set-up
 Digital signing
Consistency – Grid System
 Improvement in absolute accuracy from 0.65m to
0.05m if move from IG75 to ITM
(using static GPS obs @ 20kms)
0.7 m
0.5 m
 ITM recommended as
primary CRS by Irish
Institution of Surveyors in
2004
 Supply data in IG75 during
intervening period for legacy
systems & projects
Active GPS Network =
Passive GPS Network =
Trig Network =
IG75 (Trig Network)
0.3m
0.1 m
ITM
IG75 (Polynomial)
IG75 (7 parameter)
Consistency – Grid System
 Benefits of using ITM
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Surveys are GPS compatible
Computations simpler - no transformations
Significant improvement in absolute accuracy
Less impact of scale-factor
INSPIRE compatible
 Using Grid in Quest
 On www.osi.ie
 Standalone on own PC
 Embedded in software
 New standard test to prove new versions
from OSi & equipment suppliers
Establishing Control
 Horizontal Control – linear surveys
 GPS baselines link traverses to ITM & provide extra rigor
 Link to IG75 trig network not permitted (discontinued by OSi)
 Constraints include:
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Maximum distance between stations = 150m & maximum distance
between GPS stations = 1500m
All stations must be inter-visible to at least 2 other stations
AA < ±25mm @ 95% confidence & RA < ±5mm
GPS Stations
Traverse Stations
Establishing Control
 Vertical Control – linear surveys
 Hold 1 station fixed to GPS height in middle of network
 Double levelling loop between stations using digital levels
 AA < ±20mm &
RA < ±10mm * k (where k =√ distance in
kilometres) = ±3.9mm @ 150m
 Link to Benchmarks not permitted (discontinued by OSi)
Establishing Control
 Survey Control Report
 Description of observation methodology (Horiz & Vert)
 Description of adjustment methodology (Horiz & Vert)
 QA checks (SOPs) applied in the field and during
processing
 Results - list of deliverables as well as map products
 Certification by surveyor that information supplied is
correct & company has Professional Indemnity Insurance
 Copy of all raw data in standardised formats
Establishing Control
 Survey Control Report
 Schedule of results of control stations
ETRF89
Station
No
1
2
3
4
Lat
Long
ITM
Easting
Northing
IG75
Easting
Northing
Height Description
Malin
Head
Establishing Control
 Survey Control
Report
 Traverse Route
Diagram
 GPS Network
diagram
Establishing Control
 Survey Control Report
 Station error ellipses – quantify
magnitude and orientation metrics
of station accuracies
Establishing Control
 Survey Control Report
 Standardised location
diagrams for control
stations
Topography
 RTK not allowed for surveying topographic features
 Density of information
 10m on strings for sectioning
 10m spot level interval
 Redundant measurements – to check & prove accuracy
requirements are achieved
 Report – to include info on standard operating
procedures
Quality Control – Sources of error
 Gross Errors (blunders - measurement & computation)
 Misreading equipment, mis-recording a correct reading,
casualness, verticality of pogo, GPS observations beside
vegetation & buildings, rounding errors, …etc)
 Eliminated by using standard operating procedures
 Systematic errors (observation bias)
 Pattern in observations - causes can be identified, size of error
can be quantified - elimination by equipment calibration & P
 Random errors (normal observation errors)
 Due to range of different equipment specifications and
observer’s competency - accuracy can be quantified statistically
Quality Control – Check Surveys
 Method
 Higher order of accuracy
 Redundant measurements
 No sight of main contract values
 Use of independent contractors
 Visual inspection for missing detail
 Reporting
Check Surveys
 Reports
 Summaries for control
and detail
 Breakdown of errors and
analysis
 Problems highlighted
Auditing the digital data
 QA check list
 Analysing reports
 Visual inspection
 Topography
 Sections
 3d surface
Auditing - QA Check list
 Naming conventions
adhered to
 Model content is correct
 No duplicate points
 No crossing breaklines
 No missing breaklines
 Correct data included and
excluded from the TIN
 Accurate boundary
 Correct annotation
 etc….
Auditing – Accuracy and reports
 Accuracy tolerances appear to have been achieved
 Correct grid system has been used
 Check corrections used are consistent
 Check model is consistent with raw data
 Check all specified items have been delivered
 Check all files are digitally signed and check signatures
Dealing with non-compliant work
 Need to enforce the specification
 Good for the survey industry : Prices must be based
around meeting the specification, accepting
substandard work defeats competitive tendering
 Good for the client : Quality and consistency improve
quickly
 Re-submission is at the contractors expense
 The survey contractor should complete the QA process
prior to submittal
 Non compliant work should be rejected
Using the specification (Contractor)
 Training
 User guide
 Rationale behind specific items
 Using SCC to complete such items
 Discussion of absolute and relative accuracy
 Using SCC to process check surveys
 Analysis of failed check surveys
Using the specification (Contractor)
 Field tools
 Onboard feature
libraries
 Leica
 Trimble
 PocketDTM
 SCC
Using the specification (Client)
 Training
 Cost expectation
 Recommended usage
 QA implications for
 Check your requirements
 Accuracy
 Content
 New features by group
and category
 Output formats
 Grid
additions
 Tools
 SCC
 Crystal reports
Results to date
 Marked improvment in quality of delivered surveys
 Errors discovered by QA process
 Inconsistent application of scale
 Accuracy shortfalls
 Incorrect naming
 GPS height processing
 Failure to provide all necessary data
 Missing services
 Revisions to specification based on results
 Support for GPS control
 Changed accuracy statement
 Standardising of reports
 Additional reports
Distribution of first release
 Intended audience
 Local authorities
 Surveying bodies
 Engineers
 Survey contractors
 500 printed copied, 1,000 electronic copies
 Communications with RICS and TSA
 Available electronically from Dublin City Council
 http://www.dublincity.ie/RoadsandTraffic/QBNProject
Office/Pages/TopographicSurveySpecification.aspx
Enhancements moving forward
 Moving to open standards
 LandXML
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Broadly supported by a wide range of land survey and civil
engineering packages
Used internationally
See http://www.landxml.org/ for further information
 GML, to be included as part of the upcoming UK
Highways Agency specification
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See http://www.opengeospatial.org/standards/gml
Enhancements moving forward
 Support for related survey activities
 River surveys
 Structures, building and bridge facades
 Combined engineering / GIS surveys
 Support for emerging and changing survey technologies
 Scanners & LIDAR
 Implications of using huge datasets
 Feedback following release
 Enhancements and revisions based on project feedback
Thank you
Mr. Shane MacLaughlin
Dr. Paddy Prendergast
Managing Director
Atlas Computers Ltd
15 Moyville Lawns
Taylors Lane, Rathfarnham
Dublin 16
Tel: 00353 (1) 4958714
Email: shane@atlascomputers.ie
Web: www.atlascomputers.ie
Irish Institute of Surveyors
C/O Easons & Son (4th Floor)
40-42 Lower O'Connell Street
Dublin 1
Tel: 00353 (1) 8720194
Email: patrick.prendergast@dit.ie
Web: www.irish-surveyors.ie