a hierarchical vector data model for distributed geospatial processing
DESCRIPTION
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: - PowerPoint PPT PresentationTRANSCRIPT
A Hierarchical Vector Data Model for Distributed Geospatial
Processing
Eric B. WolfBarbara P. ButtenfieldUniversity of Colorado
at BoulderNSF BCS 0451509
Presentation for the AAG National Conference 2007
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
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
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
Ballard Strip Tree (1981)
• HierarchicalMBR
• Efficient storage search
• Complete RDP order
Creation of Strip-Trees
Presentation for the AAG National Conference 2007
MRVIN Data Structure
Presentation for the AAG National Conference 2007
Mathematical Topology
A topology on a set X is a collection T of subsets of X having the following properties:
1. Ø and X are in T
2. The union of elements of any
subcollection of T is in T
3. 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
Examples of Topologies
Equivalent Topologies Comparable Topologies
Presentation for the AAG National Conference 2007
Internal & Relative Topology
Presentation for the AAG National Conference 2007
Self-Crossing Feature
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
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
Preserving Relative Topology
Presentation for the AAG National Conference 2007
MRVIN Architecture
Presentation for the AAG National Conference 2007
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.
Future Research
Presentation for the AAG National Conference 2007