Topographic Survey Specification for Urban Projects

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Topographic Survey Specification for Urban
Projects

• Presented by
• Shane MacLaughlin, Atlas Computers Ltd
• Dr Paddy Prendergast, DIT

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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
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Background

• QBN Experience pre-2005
• Inconsistent quality of surveys
• Large amount of rework by engineers
• Delivered work not fit for purpose
• Need for improvement

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Background

• Surveyors experience
• Weak specification
• Poor statement of requirements
• Falling prices leading to falling quality
• Negative client feedback

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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

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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

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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

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Working Group
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Working Group

• Peter Muller, QBN Project Office
• Tom Curran, Dublin City Council, Survey and
  Mapping 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

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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

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Components

• Introduction and executive summary
• Specification main body
• Feature library
• User guide
• Sample reports

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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

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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 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

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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

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Consistency - Accuracy
Missing Node
Two reference points
Manifestation
Pseudo Node
Duplicate Line
Overshoot
Undershoot
Sliver
No reference point
Guptill Morrison, 1995
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Consistency - Accuracy

• Relative Absolute Accuracy

RA 0.34m RMSE ?
Building
Recorded dimension in Database 3.78m
Actual dimension on Ground 4.12m
Boundary Wall

• Relative Accuracy - closeness between the
  recorded distance between two features in a
  database and the true distance

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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)

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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

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Consistency - Output

• 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

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Consistency Grid System

• Improvement in absolute accuracy from 0.65m to
  0.05m if move from IG75 to ITM
• (using static GPS obs _at_ 20kms)

• 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
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Consistency Grid System

• Benefits of using ITM
• 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

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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
• Maximum distance between stations 150m
  maximum distance between GPS stations 1500m
• All stations must be inter-visible to at least 2
  other stations
• AA lt 25mm _at_ 95 confidence RA lt 5mm

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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 lt 20mm RA lt 10mm k (where k v distance
  in kilometres) 3.9mm _at_ 150m
• Link to Benchmarks not permitted (discontinued by
  OSi)

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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

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Establishing Control

• Survey Control Report
• Schedule of results of control stations

ETRF89 ETRF89 ITM ITM IG75 IG75 Height Description
Station No Lat Long Easting Northing Easting Northing Malin Head
1
2
3
4
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Establishing Control

• Survey Control Report
• Traverse Route Diagram
• GPS Network diagram

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Establishing Control

• Survey Control Report
• Station error ellipses quantify magnitude and
  orientation metrics of station accuracies

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Establishing Control

• Survey Control Report
• Standardised location diagrams for control
  stations

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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

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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 observers competency -
  accuracy can be quantified statistically

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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

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Check Surveys

• Reports
• Summaries for control and detail
• Breakdown of errors and analysis
• Problems highlighted

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Auditing the digital data

• QA check list
• Analysing reports
• Visual inspection
• Topography
• Sections
• 3d surface

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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.

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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

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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

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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

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Using the specification (Contractor)

• Field tools
• Onboard feature libraries
• Leica
• Trimble
• PocketDTM
• SCC

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Using the specification (Client)

• Training
• Recommended usage
• Check your requirements
• Accuracy
• Content
• New features by group and category
• Output formats
• Grid

• Cost expectation
• QA implications for additions
• Tools
• SCC
• Crystal reports

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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

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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/QBNProjec
  tOffice/Pages/TopographicSurveySpecification.aspx

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Enhancements moving forward

• Moving to open standards
• LandXML
• 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
• See http//www.opengeospatial.org/standards/gml

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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

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Thank you

• Mr. Shane MacLaughlin
• Managing Director
• Atlas Computers Ltd
• 15 Moyville Lawns
• Taylors Lane, Rathfarnham
• Dublin 16
• Tel 00353 (1) 4958714
• Email shane_at_atlascomputers.ie
• Web www.atlascomputers.ie

• Dr. Paddy Prendergast
• 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_at_dit.ie
• Web www.irish-surveyors.ie