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A Hierarchical Vector Data Model for Distributed Geospatial Processing

A Hierarchical Vector Data Model for Distributed Geospatial Processing. Eric B. Wolf Barbara P. Buttenfield University of Colorado at Boulder NSF BCS 0451509. Presentation for the AAG National Conference 2007. The Problem. Spatial data is compiled by NMAs at fixed scales:

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A Hierarchical Vector Data Model for Distributed Geospatial Processing

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  1. A Hierarchical Vector Data Model for Distributed Geospatial Processing Eric B. Wolf Barbara P. Buttenfield University of Colorado at Boulder NSF BCS 0451509 Presentation for the AAG National Conference 2007

  2. The Problem • Spatial data is compiled by NMAs at fixed scales: • E.g., 1:24,000, 1:100,000, 1:1,000,000 • Mixing fixed-scale data corrupts topology. • Incorrect generalization -> incorrect modeling output. • Lack of persistent storage for generalized representations. Presentation for the AAG National Conference 2007

  3. Our Project: MRVIN • MRVIN: Multiple Representations for Vector INformation. • A hierarchical architecture for vector geospatial data. • Provides multiple representations across a range of resolutions. • Preserves topology within each data theme and between data themes. • Sustains distributed data retrieval through standard interfaces. Presentation for the AAG National Conference 2007

  4. Previous Work • Ramer 1972, Douglas-Peucker 1973 • Ballard 1981 • Herschberger and Snoeyink 1992 • Saalfeld 1999 • Bertolotto and Egenhofer 1999 • Buttenfield 2002 Presentation for the AAG National Conference 2007

  5. Ballard Strip Tree (1981) • Hierarchical • MBR • Efficient • storage • search • Complete • RDP order

  6. Creation of Strip-Trees Presentation for the AAG National Conference 2007

  7. MRVIN Data Structure Presentation for the AAG National Conference 2007

  8. Mathematical Topology A topology on a set X is a collection T of subsets of X having the following properties: • Ø and X are in T • The union of elements of any subcollection of T is in T • The intersection of the elements of any finite subcollection of T is in T Munkres, J. R. 2000. Topology. Second ed. Upper Saddle River, NJ: Prentice Hall. P. 76. Presentation for the AAG National Conference 2007

  9. Examples of Topologies Equivalent Topologies Comparable Topologies Presentation for the AAG National Conference 2007

  10. Internal & Relative Topology Self-Crossing Feature Presentation for the AAG National Conference 2007

  11. Preserving Topology “If two convex hulls do not overlap, the contents of those hulls will not overlap.” (Saalfeld 1999) Presentation for the AAG National Conference 2007

  12. Preserving Topology in Multi-Part Features • Compound Vectors are stored as “groves” of “trees” • The convex hull for each tree is calculated and stored. • A convex hull for the grove is calculated and stored. • Saalfeld’s test is applied among all trees in each grove and among groves. Presentation for the AAG National Conference 2007

  13. Preserving Relative Topology Presentation for the AAG National Conference 2007

  14. MRVIN Architecture Presentation for the AAG National Conference 2007

  15. Future Research • Extending MRVIN to points and polygons. • Managing dimensional collapse (when a polygon becomes a line or a point) • ArcGIS script like “TerraServer Download”. • Merge MRVIN into PostGIS and extend Minnesota Map Server to create tiles from MRVIN for WMS access. • Keyhole Markup Language output for Google Earth. Presentation for the AAG National Conference 2007

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