conflation with jcs automated and human-assisted conflation using the jcs conflation suite presented...
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Conflation with JCS
Automated and Human-Assisted Conflation Using the JCS Conflation Suite
Presented at GeoTec 2003Vancouver, BC
Martin Davis, Technical Architect
Conflation with JCS
Overview of Conflation
• “Conflation” is a very broad term• Conflation problems need to be precisely
defined in order to be automated• Conflation algorithms difficult to generalize• Still awaiting “Grand Unifying Theory” of
conflation
Conflation with JCS
Overview of ConflationTerminology
• Matching – identifying features or data elements which represent the same real-world entity
• Alignment – whether two features or data elements have coincident geometry
• Adjustment – altering geometry or attributes of matched features to make them align
• Reference –dataset to be conflated to (usually of greater spatial accuracy)
• Subject – dataset to be matched or adjusted
Conflation with JCS
Overview of ConflationProblem Categorization
• Horizontal – conflation between adjacent datasets e.g. Boundary Alignment
• Vertical – conflation between datasets covering the same area e.g. Coverage Alignment, Road Network Matching
• Internal – conflation between items in a single dataset e.g. Coverage Cleaning
Conflation with JCS
Overview of ConflationAutomated VS Human-Assisted
• Automated uses algorithm(s) to match and adjust features
automatically. May not be able to fix 100% of problems
• Human-Assisted use manual editing tools to adjust features Assisted by automated tools to detect
problems, perform precise adjustment
Conflation with JCS
Overview of Conflation Workflow
• Acquire Datasets• Data Preparation & Validation (QA)• Problem Detection and Visualization• Automated Conflation• Human-assisted Conflation (if
necessary)
• Persist Updated Data
Conflation with JCS
The JCS Conflation Suite Project
• Project sponsor: Dr. Mark Sondheim - Base Mapping and
Geomatic Services Branch, MSRM
• With support from:GeoConnectionsMinistry of Sustainable Resource
Management, Province of BC
• Project Timeline Initiated: March 2002Finish: ~March 2003
Conflation with JCS
The JCS Conflation Suite
• Goals:Address real-world conflation problemsLeverage existing spatial tools and modern
software development techniquesOpen development philosophy Build toolbox for performing conflation
• JCS written in 100% pure Java• JCS is Open Source (GPL license)
Conflation with JCS
JCS Architecture
• JCS provides:APIGUI
• Built using: Java Topology Suite (JTS)Unified Mapping Platform (JUMP)
Conflation with JCS
JTS Topology Suite
• Implementation of OpenGIS Consortium Simple Features Specification
• Open-Source, 100% Java• Goals:
Fast, production quality Robust Explicit precision model
Conflation with JCS
JTS Topology SuiteGeometry Model and Operations
• Geometry model: Points, LineStrings, Polygons, collections
• Spatial predicates (using Dimensionally Extended 9-Intersection Model)
• Boolean operations, buffer, convex hull, centroid, etc.
Conflation with JCS
JUMP Unified Mapping Platform
• 100% pure Java• Open Source (GPL license)• Both API and GUI
• Goals: Rich GUI environment for developing spatial algorithms,
visualizing data and output Interactive environment for supporting human-assisted spatial
processes Leverage capabilities of Java platform for spatial processing Easily extensible
Conflation with JCS
JUMP - API
• Features with attributes and geometry• Feature Collections• Spatial Access Methods
Quadtree, STR-Tree, Binary Interval Tree
• Warping Affine Transform Bilateral Interpolated Triangulation
• Dataset I/O Well Known Text, GML, ESRI Shapefile
Conflation with JCS
JUMP Workbench• Multi-Window GUI• Supports multiple layers of spatial data; rich styling
options• Provides GUI for JUMP API functions• Geometry & Attribute editing• Easily extensible via Plugin framework
Conflation with JCS
Conflation in JCS Overview
• Provides tools for:Dataset QAProblem detectionAutomated ConflationHuman-assisted conflation (manual edits)
• Kinds of conflation algorithmsCoverage AlignmentRoad Network Matching
Conflation with JCS
Coverage AlignmentProblem Subtypes
• Boundary Alignment e.g. Municipal Parcels “Horizontal Conflation”
• Coverage Cleaning “Internal Conflation”
• General Coverage Alignment e.g. aligning suburb boundaries to
parcels “Vertical Conflation”
Conflation with JCS
Coverage AlignmentAlgorithm
• Key idea: Lines that are “close” should be identical
• Match Line segments Hausdorff distance < tolerance Relative angle < tolerance
• Adjust Vertices Snap close vertices Add or merge vertices if necessary
• Heuristics: Do not break topology Minimize change to existing vertices
Conflation with JCS
Coverage CleaningError Detection
Conflation with JCS
Coverage CleaningAutomated Alignment
Conflation with JCS
Coverage Cleaning QA of Automated Process
Conflation with JCS
Coverage CleaningManual Tools – Vertex Snapping
Conflation with JCS
Boundary AlignmentError Detection
Conflation with JCS
Boundary AlignmentAutomated Conflation
Conflation with JCS
General Coverage AlignmentError Detection
Conflation with JCS
General Coverage Alignment Automated Conflation
Conflation with JCS
Road Network MatchingProblem Example
Conflation with JCS
Road Network MatchingAlgorithm
• Match Nodes and Edges based on weighting
• Node Match weight Distance between nodes Topology match between incident edges
• Edge Match weight Hausdorff distance between edges Relative length of edges For “straight edges”, relative angle
Conflation with JCS
Road Network MatchingMatching & Visualization
Conflation with JCS
Road Network MatchingWarping based on Matching
Conflation with JCS
Further Development
• New / improved conflation algorithms Complete Road Network Matching tools Improve Coverage Alignment algorithm Alignment to natural boundaries
E.g. Admin Boundary / Heights-of-land Stream Network matching (Refractions Research)
• Additional JUMP functionality Colour-theming by attribute More flexible GML support
• JTS improvements Robustness of spatial functions, buffer