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Automated schematization using open standards, by Nottingham Uni

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  • 1. AUTOMATED SCHEMATIZATION CASESTUDY Suchith Anand Jerry Swan Mike Jackson Mark Ware
  • 2. Presentation Overview Introduction Generalization background Automated Schematization Conclusions
  • 3. The Centre for Geospatial Science (CGS) Th C t f G ti l S i Established November 2005 as a cross- faculty post-graduate research centre. Research focus: – spatial data infrastructures (SDI), – geospatial intelligence, – geospatial interoperability – location-based services. location based
  • 4. Creating Intelligent Applications Goal: Make it easier for geospatial researchers to incorporate proven geospatial techniques into their workflow. The idea is to create generic frameworks that are customized with the problem-specific details. problem specific Initial efforts have concentrated on an object-level object level optimization framework using state-space search.
  • 5. Bigger picture Maturity of open Geospatial Standards source software (for (for ex. OGC spec.) ex. OSGeo stack)
  • 6. OS Geo Product development statistics 2008 http://wiki.osgeo.org/wiki/Project_Stats
  • 7. CGS Optimization Framework • Currently implemented: – Hillclimbing, Simulated Annealing – (Reactive) Tabu Search – Simple Genetic Algorithm • Implementation targets JVM and hence easily integrated with Geotools52North WPS etc ith etc.
  • 8. Why – G h Generalization ? li i The process of simplifying the form or shape of map features, usually carried out when the map is changed from a large scale to a small scale, is referred to as generalisation. Map g p generalisation is a pprocess of extracting the important g p and relevant spatial information from reality.
  • 9. Map Generalization operators M G li ti t Simplification Amalgamation l Elimination Typification Exaggeration Displacement
  • 10. Simplification Si lifi ti Douglas-Peucker algorithm (1973)
  • 11. Amalgamation DeLucia and Black (1987) - triangulation-based area amalgamation procedures. These ideas are taken up and advanced in Jones et al (1995) Su et al (1997) - A raster-based aggregation method (forms the basis of ESRI's AreaAggregate function) Ai and van Oosterom (2002) - displacement vectors p o to a a ga at o a d a Ooste o ( 00 ) d sp ace e t ecto s prior amalgamation
  • 12. Elimination Regnauld (2001) – area features (includes deletion and aggregation of features)
  • 13. Typification f Feature clusturing - (Mackaness 1994, Ormsby and Mackaness 1999, Mackaness and Mackechnie 1999) Sester (2003) and Moulin (2003) -Kohonen Self Organizing Maps Regnauld (1996) - Minimum Spanning Trees
  • 14. Exaggeration gg Mackaness (1995) - alpha analysis for classifying urban road ac a ess ( 995) a p a a a ys s o c ass y g u ba oad networks hierarchically, providing a means for removing roads at smaller scale while still conveying essential characteristics of the network
  • 15. Displacement Lonergan and Jones (2001) - map quality is measured in terms of minimum distance violations, and polygon displacement achieved by calculating displacement vectors in an iterative fashion Li et al (2002) - polygon displacement using a two-level agent-based architecture.
  • 16. Harry Beck’s Schematic Tube Map Source: London Transport Museum
  • 17. Schematic Map - Characteristics •Topologically consistent. T l i ll i t t •Simplified lines (Douglas-Peucker). •May be desirable to re-orient lines so that they are horizontal, vertical or diagonal. •Scale in congested areas expanded at the expense of scale in areas that are less so so.
  • 18. Graphic manipulations for producing a schematic map Lines are simplified and re-oriented to conform to a regular grid. Congested areas are increased in scale at the expense of scale in areas of lesser node density
  • 19. Constraints Topological Orientation Clearance Angle Rotation Displacement Length g
  • 20. Topological Original network and derived schematic map should be topologically consistent Topological – original (Left), topological error (Middle) and acceptable solution (Right)
  • 21. Orientation If possible, network edges should lie in horizontal, vertical or diagonal direction Orientation – original (L) and schematized (R)
  • 22. Angle If possible, the angle between a pair of connected edges should be greater than some minimum angle Angle – edges re-oriented but Angle constraint violated (L) and acceptable solution
  • 23. Rotation An edge’s orientation should remain as close to its starting orientation as possible :Rotation – original (L), acceptable solution (M) and better solution (R)
  • 24. Clearance If possible, the distance between disjoint features should be g greater than some minimum distance Clearance – constraint violated (L) and resolved (R)
  • 25. Displacement Vertices should remain as close to their starting positions as possible possible. Displacement – original (L), acceptable solution (M) and better solution (R)
  • 26. Length Length – original (L) and congestion reduced by enforcing Length constraint (R)
  • 27. Core Process •Evaluate – For each vertex: Count topological errors Measure constraint violations Heuristic l i th H i ti value is the sum of the above f th b Modify Displace vertices
  • 28. Demo – Original Featureset
  • 29. Demo – Schematized Featureset
  • 30. Conclusions •Implements a usecase for automatic production of schematic maps •Proof-of-concept implemented for WFS, using schematization as transformation exemplar. p
  • 31. Thank You

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