GIS and Spatial Analysis

1. GIS and Spatial Analysis Michael F. Goodchild University of California Santa Barbara

2. Outline • GIS-oriented definitions of spatial analysis • The role of the GIS • Taxonomies of spatial analysis • A six-way classification • Issues and concerns

3. Definitions • Spatial data • information about phenomena organized in a spatial frame • the geographic frame • Methods applied to spatial data that • add value • reveal patterns and anomalies • support decisions

4. Spatial analysis • Methods whose results depend on the locations of phenomena in the frame • are not invariant under relocation • Some types of relocation may not affect social processes • rotation • relocation • inversion

5. The geographic frame • The atomic form <x,z> • Location abstracted • distance matrix • adjacency matrix • invariance under rotation, inversion, relocation

6. Spatial analysis as a collaboration • The computer as butler to the human mind • Are maps “mere”? • Humans as sources of context • cross-sectional data are already rich in context

9. The role of the GIS • The infrastructure for handling data types • to spatial data as Excel is to tables, as S-Plus is to statistical data, as Word is to text • spatial data or geographic data? • the housekeeper • the editor • The visualization tool

10. The GIS data types • Discrete geographic features • points, lines, areas • the contents of maps • with associated attributes • countable • conceived as tables with associated feature geometry • ESRI shapefiles

13. Fields • Geography as a collection of continuous variables • measured on nominal, ordinal, interval, ratio scales • vector fields of direction and magnitude • exactly one value per point • z=f(x) • population density, land ownership, zoning

17. Field representations • Raster of rectangular cells • Raster of uniformly spaced points • Irregularly spaced points • Irregular areas (polygons) • Digitized contours • Triangular mesh (triangulated irregular network or TIN) • ESRI coverages

18. GIS as a data access mechanism • The geolibrary • place-based search • integrating information about a place • making access transparent

30. Taxonomies of spatial analysis • Thousands of methods • every one a command, menu item, icon, … • Based on data type • point pattern analysis • area (polygon) analysis • analysis of interactions • Bailey and Gatrell, Haining, Unwin

31. A six-way conceptual classification • Query and reasoning • Measurement • Transformation • Descriptive summary • Optimization • Hypothesis testing

33. Queries and reasoning • Real-time answers to geographic questions • Where is…? • What is this? • How do I get from here to here? • Based on alternative views of a database

38. Measurements • Area • Distance • Length • Perimeter • Slope, aspect • Shape

40. Transformations • Buffering • Points in polygons • Polygon overlay • Spatial interpolation • Density estimation

42. City limits Areas reachable in 5 minutes Areas reachable in 10 minutes Other areas

46. Courtesy of Dick Block

47. Descriptive summary • Centers • Measures of spatial dispersion • Spatial dependence • Fragmentation • Fractional dimension

49. Optimization • Design to achieve specific objectives • Location of central point-like facilities to serve dispersed demand • Location of linear facilities • Design of boundaries for elections