1.  Data Models in Commercial GIS Systems E. Hoel, page 215-219 CSCI 5715 – Fall 2014 10/14/2014 Sameera Shah Shyam Sundar Somasundaram

2. Relevance  Week 2 - Spatial Concepts and Data Models ( Ch. 2) 2

3. Categorization Commercial GIS Data ModelsRasterVectorSpaghettiTopologyNetworkDirectedUndirectedDEM Raster DEM TIN (Vector) 3

4. Raster Model  Stores data in matrix form  Useful for data varying continuously e.g. aerial photograph  Single images  Raster Catalog  Collection of rasters Source: https://courses.washington.edu/gis250/lessons/introduction_gis/spatial_data_model.html 4

5. Vector Model (1/4)  Co-ordinate based data model  Useful for storing data that has discrete boundaries  Classified into further subtypes  Spaghetti  Network  Topological 5

6. Spaghetti Model (2/4)  Simple Data Model or Spaghetti Plot  Geometric representations have no explicit relationship  E.g. Hurricane model Source: https://ecodatarecovery.wordpress.com/tag/data-backup/ 6

7. Network Model (3/4)  One dimensional collection of point (junction) and line(edges) features  Directed e.g. water flow modeling  Hydrologic networks  Utility networks  Undirected e.g. transportation network Source: http://www.dublintunnel.ie/images/routes/dublin_map.gif 7

8. Topology Models (4/4)  Control geometric relationships  Collection of nodes, arcs, faces and their inter relationships  E.g. United States Census geographic data Source: http://docs.oracle.com/cd/B19306_01/appdev.102/b14256/sdo_topo_concepts.htm Point features (traffic signs), shown as dark circles: S1, S2, S3, and S4 Linear features (roads or streets), shown as dashed lines: R1, R2, R3, and R4 Area features (land parcels), shown as rectangles: P1, P2, P3, P4, and P5 8

9. Digital Elevation Model (DEM)  Represent the surface topography of the earth  Built from remote sensing data or survey methods  E.g. perform line-of-sight for cell phone  Classified based on type of source data as:  Raster DEM  TIN DEM 9 Source: http://www.temis.nl/data/topo/gtopo30tiles.gif

10. TIN DEM  A.k.a Vector based surface model  Contiguous non – overlapping triangles  Nodes, edges, triangles  Facilitates surface modeling 10 Source http://wtlab.iis.u-tokyo.ac.jp/~wataru/lecture/rsgis/rsnote/cp6/6-10-2.gif

11. Future Directions  Available data for specific times /dates  Augment existing data models to support temporal data 11

12. References  Data Models in Commercial GIS Systems, E. Hoel, page 215-219  Spatial Databases: A Tour, S. Shekhar and S. Chawla, Prentice Hall, 2003 12

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