Spatial AnalysisDescription and AnalysisProcess, Pattern and AnalysisSpatial Analysis: successive levels of sophisticationGeoStatistics & Spatial StatisticsThe Pitfalls of Spatial AnalysisFundamental Spatial ConceptsImplementing Spatial Analysis in ArcGIS 9DifferencesAnalysis Tools in ArcToolboxThe Components of An Analysis and the elements of its documentationLiterature ReviewDoing a Literature ReviewHow to Format Citations1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas1Spatial AnalysisAn Introduction to Concepts and theirImplementation in ArcMap1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas2Description and Analysis•Most GIS systems are acquired by large organizations for the purpose of representing and describing features of the real world which are relevant to that organization’s mission–Spatial databases perform this function–Most concepts discussed so far relate to this•Points, lines, polygons concepts for representation•Coordinate systems as fundamental properties of spatial data•geographic file formats for storageMost GIS system capabilities are focused here•Analysis involves gaining an understanding of the patterns, and associated cause and effect processes, underlying the features which have been described in order to–Help the organization better carry out its mission•Make better decisions, for example–Understand the phenomena as a goal in itself•This is the role of scienceGIS systems are less capable here, and often must be supplemented1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas3Process, Pattern and Analysis•Processes operating in space produce patterns•Spatial Analysis is aimed at:–Identifying and describing the pattern–Identifying and understanding the process1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas4Spatial Analysis: successive levels of sophistication•Spatial data manipulation: classic GIS capabilities–Spatial queries & measurement, buffering, map layer overlay•Spatial data analysis: descriptive and exploratory–Visualization through data manipulation and mapping•John Snow’s maps of cholera in 1850s London•Spatial statistical analysis: hypothesis testing–Are data “to be expected” or are they “unexpected” relative to some statistical model, usually of a random process•Spatial modeling: prediction–Constructing models (of processes) to predict spatial outcomes (patterns)–What if analyses1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas5GeoStatistics & Spatial StatisticsObject View•The real world is a series of entities located in space.–An object is a digital representation of an entity•Objects analyzed with Spatial Statistics–The focus of this courseField View•The real world has properties which vary continuously over space–every place has a value•Fields analyzed with GeoStatistics–The focus of the Spatial Analysis course1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas6The Pitfalls of Spatial Analysis•Spatial autocorrelation–Data from location near to each other are more likely to be similar than data from location remote from each other–Causes serious problems with traditional statistical models•Spatial statistical models are essential•Modifiable areal unit problem (MAUP)–Results may depend on the areal unit used•Census tracts versus counties (scale issue)•Census tracts versus zip codes (not a scale issue)•Ecological fallacy–Results obtained from aggregated data (e.g. census tracts) cannot be assumed to apply to individual people–A special case of the MAUP problem–Encountered in spatial and non-spatial analysis•Scale affects representation and results–Cities may be points or polygons–MAUP may be viewed as a scale issue•Nonuniformity of Space and Edge Issues–Phenomena is not distributed evenly in space•Bank robberies cluster ‘cos banks are clustered in space–Edges, beyond which there is no data, can significantly effect results1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas7Fundamental Spatial Concepts•Distance–The magnitude of spatial separation–Euclidean (straight line) distance often only an approximation•Adjacency–Nominal or binary equivalent of distance–Levels of adjacency exist: 1st, 2nd, 3rd nearest neighbor, etc..•Interaction–The strength of the relationship between entities–An inverse function of distance•Neighborhood–An association between one entity and those around it–May be based upon•Interaction: flows or connections (functional)•Similarity of attributes (formal)1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas8Primarily carried out in ArcMap:•via Selection/Select by Location–this selects features of one layer(s) which relate in some specified spatial manner to the features in another layer –if desired, selected features may be saved later to a new theme via Data/Export Data–Individual features are not themselves modified•via Spatial Join (right click layer in T of C, select Join/Joins and Relates, then click down arrow in first line of Join Data window---see Joining Data in Help for details)–Use for: points in polygon (identifies polygon in which point is located)lines in polygon (identifies polygons crossed by line)points on lines (to calculate distance to nearest line)points on points (to calculate distance to “nearest neighbor” point)–operate on tables and normally creates a new table with additional variables, but again does not modify spatial features themselves•via ArcToolbox –Generally these tools modify geographic feature, thus they create a new layer (e.g. shape file)–Tools are organized into multiple categoriesImplementing Spatial Analysis in ArcGIS 91/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas9Differences•Selection: simply selects (“highlights”) entire spatial features in the target layer, but doesn’t modify these features–Selection only–Only Selected features (a subset of all features) are “output”–No new output file saved unless you use Export/data•joins: operate on tables and normally creates a new table with additional fields or variables (columns), but again does not modify actual spatial features (rows) –adds attributes (columns) to the layer’s table from another layer’s table–All features are “output”–No features modified–No new output file saved unless you use Export/data•Analysis Toolbox (and others) in ArcToolbox –Often these modify or create