It’s the Geography, Cupid!
Embed Size (px)
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!
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
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
Operational ModelANSI-SPARC Model for software development
Operational ModelANSI-SPARC Model for software developmenthow we systematically define ideasGIS are Systems to Model the World
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
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
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