It’s the Geography, Cupid!

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It’s the Geography, Cupid!. GTECH 201. Lecture 04 Introduction to Spatial Data. Today’s Content. Types of spatial data World models Spatial data models Spatial data structures The geo-relational principle. Types of Spatial Data. Locations or regions Relative positions - PowerPoint PPT Presentation

Transcript of It’s the Geography, Cupid!

  • Its the Geography, Cupid!

  • GTECH 201Lecture 04 Introduction to Spatial Data

  • Todays ContentTypes of spatial dataWorld modelsSpatial data modelsSpatial data structuresThe geo-relational principle

  • Types of Spatial DataLocations or regionsRelative positionsPoints, lines, or areasRegular vs. irregularContinuous vs. discrete

  • Geostatistical Data aka random field dataMeasurements taken at fixed locationsSpatially continuousSmall-scale variationToblers Law of Geography

  • Lattice DataRegular latticeSatellite imageIrregular latticePolygon map

  • Spatial Point PatternsDistribution of locations e.g., bald eagles or earth quakes

  • Why do we Need Models?It wont fit!

  • Vector View

  • Raster / Image View

  • What is where? versus Where is what?What is where? Vectorspace is occupied by objects that are described by their attributes Where is what? Rastervariation of an attribute as a continuous field

  • Raster VectorEach world view presents different aspects of the real worldThus we can:ask different questions (e.g. apply different operations)get different answers (e.g. apply different analytical tools)

    .. so choose carefully

  • Raster Vector continuedConverting between the raster and vector data models results in error

  • Chrismans Spheres

  • ANSI-SPARC Model for Software DevelopmentGIS are systems to model the worldUser Model Conceptual Model Operational Model

  • GIS are Systems to Model the World

    User Model how we intuitively think

    Conceptual Model

    Operational ModelANSI-SPARC Model for software development

  • User Model

    Conceptual Model

    Operational ModelANSI-SPARC Model for software developmenthow we systematically define ideasGIS are Systems to Model the World

  • User Model

    Conceptual Model

    Operational Model

    how we fuse systematic thinking into a technologically defined contextGIS are Systems to Model the World

  • The ANSI/SPARC Model and Chrismans Spherescomputer sciencegeoinformation theoryapplication disciplines

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

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

  • Vector Data ModelsSpaghetti 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

  • Raster ModelsPros : Simple, computer friendly, scanner friendly, field- friendly, compressibleCons : Large, unstructured, inflexible

  • Vector ModelsPros : Structure, cognitive consonance(!), compactness(?), accuracyCons : Inflexibility, complexity, spuriously precise(?), atemporal

  • Object-centered ModelsPros : Structure, power, potential process links, consistency(?)Cons : Extreme complexity, power hungry

  • Data Structure

  • AttributesForest Inventory

  • Geo-Relational Principle

  • Database Relations

  • Further ReadingANSI/SPARC modelLaurini & Thompson. Fundamentals of GIS, p.357-362Chrismans SpheresChrisman, N. 1997. Exploring Geographic Information SystemsKey Text for ConceptsDe Mers, M. 2004. Fundamentals of Geographic Information Systems. NY: John Wiley & Sons