Topographic Survey Specification for Urban Projects

Topographic Survey Specification for Urban ProjectsPresented by Shane MacLaughlin, Atlas Computers LtdDr Paddy Prendergast, DITOverview

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

BackgroundQBN Experience pre-2005Inconsistent quality of surveysLarge amount of rework by engineersDelivered work not fit for purposeNeed for improvement

BackgroundSurveyors experienceWeak specificationPoor statement of requirementsFalling prices leading to falling qualityNegative client feedbackBackgroundQBN topographic specification Developed by Atlas Computers Ltd in conjunction with Dublin City Council QBN project officeRigorously enforced consistency based on use of SCC softwareBased on IG75 gridPresented at Survey Ireland 2007 conferenceMet stated objectives but had shortcomings

Shortcomings in 2007 specLack of explicit QA/QC proceduresLack of illustrative documentation for the contractorBased on old IG75 grid rather than new gridBased on implicit requirements through provision of SCC feature library

New specificationOvercome the shortcomings of the previous specificationGeneralise the scope to include similar worksForm a working group representing the interests of all parties and including the necessary expertise to represent those interestsWorking Group

Working GroupPeter Muller, QBN Project OfficeTom Curran, Dublin City Council, Survey and Mapping DepartmentShane MacLaughlin (Chair) and ine Martin, Atlas Computers LtdDr Paddy Prendergast, Irish Institute of SurveyorsTom Mulreid, Apex Surveys and Society of Chartered SurveyorsVincent Molloy, Local Government Computer Services BoardRay Murphy and Stan Schoene, Murphy Surveys LtdGerry Healy, RPS Consulting Engineers

ObjectivesInclude documented QA/QC procedures to verify the quality of the delivered productProvide consistent results in terms of content, accuracy, and outputMove from IG75 to ITM while continuing to support IG75Achievable by the survey contractorsCost effective for the clientComponentsIntroduction and executive summarySpecification main bodyFeature libraryUser guideSample reports

Quality AssuranceWhat is quality?ISO 9000 Say what you do, do what you say, and be able prove itconformance to requirements Phillip CrosbyTo 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 WeinbergQuality is subjective and exists within the context of providing value to a given audience.Staying in business - W Edwards DemingQuality 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 specificationEnsure all client requirements are clearly and unambiguously statedDesigned such that necessary checks and procedures are included to ensure that work being delivered meets stated requirementsProviding 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 scopeConsistency - ContentFeature library Naming conventionsColours, layers, stylesAnnotationSignificance to the DTMOutput conventions to CAD, MX, etcField implications1,2 and 3 point featuresStrings and geometry

Consistency - AccuracyMissing NodeTwo reference pointsPseudo NodeOvershootNo reference pointGuptill & Morrison, 1995Duplicate LineSliverUndershootManifestationConsistency - AccuracyRelative & Absolute Accuracy

Boundary WallBuildingRecorded dimension in Database = 3.78mActual dimension on Ground = 4.12mRelative Accuracy - closeness between the recorded distance between two features in a database and the true distance RA = 0.34mRMSE = ?True Position333333.000mE, 333333.402mNRecorded Position333333.333mE, 333333.333mNAbsolute Accuracy - closeness of recorded position (coords) to its true position (Most Probable Value) use GPSAA = 0.34mRMSE = ?Consistency - AccuracyHorizontal & Vertical Accuracy - ControlAbsolute - 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 detailAbsolute - width of pogo stick beside wall & trying to hold pogo vertical rather than centreline ~10cmRelative - +/- 10cm at one end and +/-10cm at other end = +/-20cmHard & soft surfaces - block wall versus overgrown hedge with fence (horiz) or paved road versus ploughed field (vert)Consistency - AccuracyAccuracy (repeatability) - daily repeatability test by University of Melbourne (Gordini et al., 2006) - differences in metres between true value and VRS solutions

Single shot NRTK observations are not suitable for survey controlMust be static observations, for a set period & post processedEastingsNorthingsEllipsoidal HeightsConsistency - OutputCartographyTIN ground modelSectionsDeliverables CAD,SCC,MXRaw dataReportsMain survey reportCorrection, reduction and adjustment detailsStation locationInstrument set-upDigital signing

Consistency Grid SystemImprovement in absolute accuracy from 0.65m to 0.05m if move from IG75 to ITM(using static GPS obs @ 20kms)0.1 m0.3m0.5 m0.7 mIG75 (Trig Network)IG75 (7 parameter)ITMIG75 (Polynomial)Active GPS Network =Passive GPS Network = Trig Network = ITM recommended as primary CRS by Irish Institution of Surveyors in 2004Supply data in IG75 during intervening period for legacy systems & projects

Consistency Grid SystemBenefits of using ITMSurveys are GPS compatibleComputations simpler - no transformationsSignificant improvement in absolute accuracyLess impact of scale-factorINSPIRE compatibleUsing Grid in QuestOn www.osi.ie Standalone on own PCEmbedded in softwareNew standard test to prove new versions from OSi & equipment suppliersEstablishing ControlHorizontal Control linear surveysGPS baselines link traverses to ITM & provide extra rigorLink to IG75 trig network not permitted (discontinued by OSi)Constraints include:Maximum distance between stations = 150m & maximum distance between GPS stations = 1500mAll stations must be inter-visible to at least 2 other stationsAA < 25mm @ 95% confidence & RA < 5mm GPS StationsTraverse StationsEstablishing ControlVertical Control linear surveysHold 1 station fixed to GPS height in middle of networkDouble levelling loop between stations using digital levelsAA < 20mm & RA < 10mm * k (where k = distance in kilometres) = 3.9mm @ 150mLink to Benchmarks not permitted (discontinued by OSi)

Establishing ControlSurvey Control ReportDescription of observation methodology (Horiz & Vert)Description of adjustment methodology (Horiz & Vert)QA checks (SOPs) applied in the field and during processingResults - list of deliverables as well as map productsCertification by surveyor that information supplied is correct & company has Professional Indemnity InsuranceCopy of all raw data in standardised formatsEstablishing ControlSurvey Control ReportSchedule of results of control stationsETRF89ITMIG75HeightDescriptionStation NoLatLongEastingNorthingEastingNorthingMalin Head1234Establishing ControlSurvey Control ReportTraverse Route DiagramGPS Network diagram

Establishing ControlSurvey Control ReportStation error ellipses quantify magnitude and orientation metrics of station accuracies

Establishing ControlSurvey Control ReportStandardised location diagrams for control stations

TopographyRTK not allowed for surveying topographic featuresDensity of information10m on strings for sectioning10m spot level intervalRedundant measurements to check & prove accuracy requirements are achievedReport to include info on standard operating proceduresQuality Control Sources of errorGross 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 proceduresSystematic errors (observation bias)Pattern in observations - causes can be identified, size of error can be quantified - elimination by equipment calibration & PRandom errors (normal observation errors)Due to range of different equipment specifications and observers competency - accuracy can be quantified statisticallyQuality Control Check SurveysMethodHigher order of accuracyRedundant measurementsNo sight of main contract valuesUse of independent contractorsVisual inspection for missing detailReportingCheck SurveysReportsSummaries for control and detailBreakdown of errors and analysisProblems highlighted

Auditing the digital dataQA check listAnalysing reportsVisual inspectionTopographySections 3d surface

Auditing - QA Check listNaming conventions adhered toModel content is correctNo duplicate pointsNo crossing breaklinesNo missing breaklinesCorrect data included and excluded from the TINAccurate boundaryCorrect annotationetc.

Auditing Accuracy and reportsAccuracy tolerances appear to have been achievedCorrect grid system has been usedCheck corrections used are consistentCheck model is consistent with raw dataCheck all specified items have been deliveredCheck all files are digitally signed and check signatures

Dealing with non-compliant workNeed to enforce the specificationGood for the survey industry : Prices must be based around meeting the specification, accepting substandard work defeats competitive tenderingGood for the client : Quality and consistency improve quickly Re-submission is at the contractors expenseThe survey contractor should complete the QA process prior to submittalNon compliant work should be rejected

Using the specification (Contractor)TrainingUser guideRationale behind specific itemsUsing SCC to complete such itemsDiscussion of absolute and relative accuracyUsing SCC to process check surveysAnalysis of failed check surveys

Using the specification (Contractor)Field toolsOnboard feature librariesLeicaTrimblePocketDTMSCC

Using the specification (Client)TrainingRecommended usageCheck your requirementsAccuracyContentNew features by group and categoryOutput formatsGrid

Cost expectationQA implications for additionsToolsSCCCrystal reportsResults to dateMarked improvment in quality of delivered surveysErrors discovered by QA processInconsistent application of scaleAccuracy shortfallsIncorrect namingGPS height processingFailure to provide all necessary dataMissing servicesRevisions to specification based on resultsSupport for GPS controlChanged accuracy statementStandardising of reportsAdditional reportsDistribution of first releaseIntended audienceLocal authoritiesSurveying bodiesEngineersSurvey contractors500 printed copied, 1,000 electronic copiesCommunications with RICS and TSAAvailable electronically from Dublin City Councilhttp://www.dublincity.ie/RoadsandTraffic/QBNProjectOffice/Pages/TopographicSurveySpecification.aspx

Enhancements moving forwardMoving to open standardsLandXML Broadly supported by a wide range of land survey and civil engineering packagesUsed internationally See http://www.landxml.org/ for further informationGML, to be included as part of the upcoming UK Highways Agency specificationSee http://www.opengeospatial.org/standards/gml

Enhancements moving forwardSupport for related survey activitiesRiver surveysStructures, building and bridge facadesCombined engineering / GIS surveysSupport for emerging and changing survey technologiesScanners & LIDARImplications of using huge datasetsFeedback following release Enhancements and revisions based on project feedback Thank youMr. Shane MacLaughlin Managing DirectorAtlas Computers Ltd15 Moyville LawnsTaylors Lane, RathfarnhamDublin 16Tel: 00353 (1) 4958714Email: shane@atlascomputers.ieWeb: www.atlascomputers.ie

Dr. Paddy PrendergastIrish Institute of SurveyorsC/O Easons & Son (4th Floor)40-42 Lower O'Connell StreetDublin 1Tel: 00353 (1) 8720194Email: patrick.prendergast@dit.ieWeb: www.irish-surveyors.ie