Maintaining boundary relationships within spatial databases

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Maintaining boundaryrelationships within
spatialdatabases
Lesley Arnold Landgate Email lesley.arnold_at_landgat
e.wa.gov.au
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Case Studies
Strategy
Introduction
Problem
Conclusion
Management
What Next
Concepts
Introduction

• Administrative, operational and cadastral
  boundaries
• are often coincident in reality

• 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

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
States 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

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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

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Strategy
Introduction
Case Studies
Problem
Conclusion
Management
What Next
Concepts
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

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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.

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
Topological concepts

• Topology refers to knowledge about relative
  positioning of spatial features
• Topological representations modeled in terms of
• Network Connectivity
• Planar Containment, Adjacency, Disjoint

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
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

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
Referential Topology Management

• Two main approaches
• Using Topology Data Management Toolsets/rules
• Building topological relationships within spatial
  databases

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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

CAD
New Data
ADMIN
Primary Geographic Database
Topological validation
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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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

New Data
Topological validation
Primary Geographic Database
Error resolution
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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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

X
SLIP Users
Agency users/ editors
Data Copy
Primary Geographic Database
Data version or incremental update
Agency Database
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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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

?
SLIP Users
Internal users and editors
Primary Geographic Database
Boundary data changes managed automatically
Agency Primary Database
One off database replication
Agency Boundary Data
Trickle feed updates
Agency data editors
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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
What Next
Concepts
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

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
Concepts
What Next
Positional Accuracy Improvement Group

• Coordinator Jenny Smith - Jenny.smith_at_walis.wa.g
  ov.au
• 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

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Introduction
Case Studies
Strategy
Problem
Conclusion
Management
Concepts
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

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Introduction
Case Studies
Strategy
Problem
Management
Conclusion
What Next
Concepts
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
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Thank you
Lesley Arnold Landgate Email lesley.arnold_at_landgat
e.wa.gov.au