Spatial Analysis:ArcGISArcGIS Modules or ComponentsThe Levels of ArcGISImplementing Spatial Analysis in ArcGIS 9DifferencesAnalysis Tools in ArcToolboxObjectiveMethod 1: all schoolsHypothesis 1Method 2: schools within buffer onlyHypothesis 2Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 281/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas 1Spatial Analysis:Implementation in ArcGISArcGIS•Most common software used for GIS•From ESRI, Inc (Environmental Systems Research Institute. Inc.) in Redlands, CA–Founded and owned by Jack Dangermond•Released ArcInfo in 1971, the first commercial vector-based GIS system•Three main modules– ArcMap for map production and analysis–ArcCatalog for data management–ArcToolbox contains all the tools in ArcMap and ArcCatalog, plus many moreArcGIS Modules or Components•ArcMap –for map production and analysis•ArcCatalog –for data management•ArcToolbox –contains all the tools in ArcMap and ArcCatalog, plus many moreEach has a different user interfaceThe Levels of ArcGISCosts more $sDoes more•ArcView •Map production and analysis •ArcEditor•Data creation•ArcInfo•High level analysisEach has the same user interface1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas 5Primarily 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 as a new layer using Data/Export Data–geographic features are not themselves modified•via Spatial Join (right click layer in Table of Contents , select Join/Joins and Relates, then click down arrow in first line of Join Data window)–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 point)–operate on tables and normally creates a new table with additional variables, but again does not modify geographic features•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-Dallas 6Differences•Selection: simply selects spatial features–Spatial features are not modified.–Selected features are highlighted on map and in the table–No new output file saved unless you use Export/data•joins: operate on tables and normally adds additional fields or variables (columns), but again does not modify actual spatial features (rows) –Normally, adds attribute variables (columns) to one layer’s table from another layer’s table–All geographic features are “output” and no features are modified–No new output file saved unless you use Export/data•Analysis Toolbox (and others) in ArcToolbox –Often these modify or create spatial features thus they output new spatial filesDifferent approaches can be used, in some cases, to produce same results.1/3/2008 GISC 6382 Applied GIS Briggs UT-Dallas 7Analysis Tools in ArcToolboxArcToolbox, particularly the Analysis Tools toolbox contains•Extract toolset, including–Clip which limits one layer to the exact outer boundary of another layer(e.g. limit a Texas road layer to Dallas county only)•Overlay toolset, including–Intersect, which combines two polygon layers--with output limited to common area–Union, which combines two polygon layers--with output covering full extent of both layers•Proximty toolset, including–Buffer, for creating buffer polygons at a specified distance around points, lines or polygons–Point Distance, for calculating distances between points within a specified radius•Statistics toolset, including–Frequency, which gives you counts of attribute value combinations–Summary Statistics, which gives you summary descriptive statistics for columns in a table, including sum, mean, min, max, etc..Tools useful for analysis of vector data are located in other toolsets as well!!! For example: –Data Management Tools>Generalization, contains•Dissolve, which removes boundaries between polgyonsObjective•The objective of the research is to answer the question: Are certain groups (the poor, or racial and ethnic minorities) more exposed to pollution than the population as a whole?Method 1: all schools•We have data for Dallas, TX on:–Toxic emission sites–Demographic characteristics of schools •We will create a 1 mile buffer around each toxic site•We will compare the demographic characteristics of schools within the buffer to those outside the bufferHypothesis 1•Null Hypothesis: there will be the same percentage for each demographic group beyond and within the buffer•Alternative hypotheses: there will be a higher percentage of Black, Low Income, Hispanic, and Asian students, and a lower percentage of white students within the buffer.Method 2: schools within buffer only•We have data for Dallas, TX on:–Toxic emission sites–Demographic characteristics of schools •We will create a toxicity score for each school within 1 mile of a toxic site based on distance to the toxic site and the toxicity of the site •We will compare the demographic characteristics of the ten (10) schools with the highest scores to the rest of the schools within the buffer.Hypothesis 2•Null Hypothesis: there will be the same percentage for each group in the Top Ten schools compared with the rest of the buffer schools•Alternative hypotheses: there will be a higher percentage of Black, Low Income, Hispanic, and Asian students and a lower percentage of white students in the Top Ten toxic schools.1. Bring in the data files (C:\Users\briggs\Documents\china\lectures\project-armap\data)Dal_toxic_SPCS,shp contains the toxic sites and their toxicity scoresDal_school_SPCS.shp contains the location of the schoolsHighways_NCTCOG_SPCS.shp contains major roads in the Dallas Fort Worth area County_NCTCOG.shp contains the county outlines for the counties in the Dallas/Fort Worth areaDal_sch_stats.dbf contains the demographic statistics2. Identify school within 1 mile of toxic sites-- use Selection>Select by location to select all schools within distance of 1 mile (5280 feet) from Dal_toxic--select features