Maintaining boundary relationships within spatial databases Lesley Arnold Landgate

Conclusion What Next Management Case StudiesStrategy Concepts Introduction Problem Need to manage co-linearity – with in spatial databases – between agency data sets Misalignment due to: – different levels of data capture precision and accuracy – varying degrees of data currency – conflicting business needs Problem exacerbated by need to spatially upgrade cadastre Problem exposed through SLIP Administrative, operational and cadastral boundaries are often coincident in reality Introduction

The Misalignment Problem Creates an overhead in data maintenance –Ad hoc changes logistically difficult to manage –New data must be duplicated and managed in multiple databases –Agencies apply data shifts to keep data synchronised Misalignment causes uncertainty in data usage Results of geographic analysis are invalid – spatial queries retrieve incorrect results – incorrect area calculations Conclusion What Next Management IntroductionCase StudiesStrategy Concepts Problem

State’s Cadastral Database SCDB is a dynamic database –Integration of new surveys 500 new surveys per month 69% automatically integrated –Spatial upgrades (87% complete) Digitised points reduced by 5500 points/month 210,000 points remaining –ad hoc anomaly resolution –Administration boundaries updated –New representations of coastline and inland waters –Roads voids being polygonised Conclusion What NextConcepts Problem IntroductionCase Studies Management Strategy

Department of Planning Metropolitan and Regional Planning Scheme Boundaries Cadastre is used as a reference base for all planning products Misaligned boundary data issues –Poor presentation –Slivers and incorrect information –planning decisions ambiguous –misalignment with aerial imagery –Incorrect SLIP – Interest Enquiry – decisions –Multiple versions of cadastre stored –high costs of managing spatial discrepancies Conclusion What NextConcepts Problem IntroductionCase Studies Management Strategy

Water Corporation Manages the States Water Supply Network –Maintain a land parcel data layer –Water pipelines, sewers and connection points are offset from land parcel boundaries Conclusion What NextConcepts Problem IntroductionCase Studies Management Strategy

Water Corporation Mismatch between Water Corp land parcel data and cadastre Periodic shift vectors applied to maintain object relationships Linear objects not always reconcilable Sliver polygons between cadastre and planning boundaries Use of imagery increases perception of error Water Corp customers subjected to data shifts Conclusion What Next Management Strategy Concepts Problem IntroductionCase Studies

Strategy Cross government strategies require a Sustainable Approach –Development of real time business processing consistent data currency across the geographic data sets accurate data for social, economic and environmental decision making –Use of robust, flexible and cost effective systems that enable efficient data validation economical technology renewal reuse of data, processes and workflows –Use of automation to address human and technology resource constraints –Participatory model to ensure the longevity and usage of data resources, systems and products well into the future. Conclusion What Next Management Concepts Problem IntroductionCase StudiesStrategy

Topological concepts Topology refers to knowledge about relative positioning of spatial features Topological representations modeled in terms of –Network Connectivity –Planar: Containment, Adjacency, Disjoint Conclusion What Next Management Problem IntroductionCase StudiesStrategy Concepts

Topological concepts Planar Topology = rubber sheeting effect –Relationship of each piece of data does not change – adjacency maintained –Same number of pieces, same order –Edges match retained Conclusion What Next Problem IntroductionCase StudiesStrategy Concepts Management

Referential Topology Management Two main approaches 1.Using Topology Data Management Toolsets/rules 2.Building topological relationships within spatial databases Conclusion What Next Problem IntroductionCase StudiesStrategy Concepts Management

Referential Topology Management Using Topology Data Management Toolsets/rules Persisted topological structures Geometry stored as nodes, edges, faces Data validation is pre-processed Time consuming to bring together agency data sets Example: 1Spatial Radius Topology Primary Geographic Database Topological validation CAD ADMIN New Data Conclusion What Next Problem IntroductionCase StudiesStrategy Concepts Management

Referential Topology Management Building topological relationships within spatial databases Suited to managing data within a single database No topology is stored only the user defined rules Geometry stored as coordinate pairs Topology maintained during editing Example ESRI Geodatabase Relational Implementation Topological validation New Data Primary Geographic Database Error resolution Conclusion What Next Problem IntroductionCase StudiesStrategy Concepts Management

Traditional Boundary Management Agency Users must manage –Conflation between data sets –Management of incremental updates or redo version enhancements –Boundary maintenance as topological relationships not possible Primary Geographic Database Agency Database Data Copy Agency users/ editors Data version or incremental update SLIP Users X Conclusion What Next Problem IntroductionCase StudiesStrategy Concepts Management

Data Hosting and Direct Editing Approach – integrated data sets – requires same software solution Referential topology between boundary data managed via sematic relationships and logical adjacency Benefit to state: Topologically correct integrated boundary data Agency Boundary Data One off database replication Primary Geographic Database Trickle feed updates Internal users and editors Agency data editors Agency Primary Database SLIP Users Boundary data changes managed automatically Conclusion What Next Problem IntroductionCase StudiesStrategy Concepts Management

Native Title Spatial Services (NTSS) Experience Native Title Boundaries are aligned to cadastre or prescribed coordinates NT Data critical to accurate interrogation (SLIP IE) Approach: NTSS data hosted in SCDB –4 additional boundary admin layers - shared line usages –135 NT Applications/Determinations/ Indigenous Land Use Agreements –composed of 62,000 lines, 40% are linked to cad lines –cost $45,000 plus 2 FTEs for six months SmartPlan –Tools for the creation and maintenance of the NT datasets –Referential topology rules trigger cadastral boundary changes to NT boundaries automatically –Changes associated with permanent points are manually adjusted via automatic notifications Conclusion What Next Problem IntroductionCase StudiesStrategy Concepts Management

Positional Accuracy Improvement Group Coordinator Jenny Smith - Cross Agency Representation Department of Planning Department of Minerals and Petroleum Water Corporation Department of Conservation and Environment Department of Water Landgate National Native Title Tribunal Local Government Representative Also represented SLIP IE Native Title Spatial Services Aerial Photography Topography Database Conclusion Problem IntroductionCase StudiesStrategy Concepts Management What Next

Positional Accuracy Improvement Group Draft Terms of Reference Best Practise Data Management Managing relationships between boundary data sets Emphasis on States Cadastral Data Set Strategies Bring forward completion of the Spatial Cadastral Upgrade Ad hoc upgrades are logistically more difficult to mange than new subdivisions Partnerships arrangements required Develop processes, such as the supply of shift vectors, to manage integration of spatially upgraded data Examine software solutions to better manage boundary relationships Conclusion Problem IntroductionCase StudiesStrategy Concepts Management What Next

Conclusion Maintaining boundary relationships in spatial databases is a challenge that requires significant cooperation and commitment across government agencies With this in mind it is important to have a clear shared vision on how data can be managed more strategically, and importantly, how we can incorporate sustainability principles into out data management processes What Next Problem IntroductionCase StudiesStrategy Concepts ManagementConclusion

Thank you Lesley Arnold Landgate