It’s the Geography, Cupid! - PowerPoint PPT Presentation

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It’s the Geography, Cupid!

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  1. It’s the Geography, Cupid!

  2. GTECH 201 Lecture 04Introductionto Spatial Data

  3. Today’s Content • Types of spatial data • World models • Spatial data models • Spatial data structures • The geo-relational principle

  4. Types of Spatial Data • Locations or regions • Relative positions • Points, lines, or areas • Regular vs. irregular • Continuous vs. discrete

  5. Geostatistical Data –aka random field data • Measurements taken at fixed locations • Spatially continuous • Small-scale variation • Tobler’s Law of Geography

  6. Regular lattice Satellite image Irregular lattice Polygon map Lattice Data

  7. Spatial Point Patterns • Distribution of locations • e.g., bald eagles or earth quakes

  8. Why do we Need Models? It wont fit!

  9. Vector View

  10. Raster / Image View

  11. What is where? versus Where is what? • “What is where?” – Vector space is occupied by objects that are described by their attributes • “Where is what?” – Raster variation of an attribute as a continuous field

  12. Raster Vector • Each world view presents different aspects of the “real” world • Thus we can: • ask different questions (e.g. apply different operations) • get different answers (e.g. apply different analytical tools) …….. so choose carefully

  13. Raster Vector continued • Converting between the raster and vector data models results in error

  14. Chrisman’s Spheres

  15. ANSI-SPARC Model for Software Development GIS are systems to model the world User Model Conceptual Model Operational Model

  16. GIS are Systems to Model the World User Model – how we intuitively think Conceptual Model Operational Model ANSI-SPARC Model for software development

  17. GIS are Systems to Model the World User Model Conceptual Model Operational Model ANSI-SPARC Model for software development how we systematically define ideas

  18. GIS are Systems to Model the World User Model Conceptual Model Operational Model how we fuse systematic thinking into a technologically defined context

  19. context discipline spatial modeling conceptual modeling logical data modeling physical data modeling OPERATIONAL The ANSI/SPARC Model and Chrisman’s Spheres application disciplines geoinformation theory computer science

  20. Digital Maps as Models • Representing a complex reality • Continuous variation • Spatial Data: spatial, temporal and thematic • Data Models

  21. What sort of Models are These? • Raster Model - The world as regular tessellations defined by areal property • Vector Model - The world as points, lines, areas and attributes….. making objects • Object Model - The world as interacting entities with spatial dimensions

  22. Vector Data Models • Spaghetti model • Topological models A file of spatial data that is a just a collection of co-ordinate strings. Each entity (or piece of spaghetti) is represented by one data entry. There is no topology. Topology refers to the spatial relationships between objects. The topological model represents spatial relationships such as: - length - area - connectivity - contiguity

  23. Raster Models Pros : Simple, computer friendly, scanner friendly, field- friendly, compressible Cons : Large, unstructured, inflexible

  24. Vector Models Pros : Structure, cognitive consonance(!), compactness(?), accuracy Cons : Inflexibility, complexity, spuriously precise(?), atemporal

  25. Object-centered Models Pros : Structure, power, potential process links, consistency(?) Cons : Extreme complexity, power hungry

  26. Data Structure

  27. unique stand number dominant cover group avg. tree height stand site index stand age 001 deciduous 3 G 100 002 dec/con 4 M 80 003 dec/con 4 M 60 004 coniferous 4 G 120 Attributes Forest Inventory

  28. Geo-Relational Principle

  29. Database Relations

  30. Further Reading ANSI/SPARC model Laurini & Thompson. Fundamentals of GIS, p.357-362 Chrisman’s Spheres Chrisman, N. 1997. Exploring Geographic Information Systems Key Text for Concepts De Mers, M. 2004. Fundamentals of Geographic Information Systems. NY:John Wiley & Sons