空间统计书单4arcgisimpl

1、1/3/2008GISC 6382 Applied GIS Briggs UT-Dallas1Spatial Analysis:Implementation in ArcGISArcGISMost common software used for GISFrom ESRI, Inc (Environmental Systems Research Institute. Inc.) in Redlands, CAFounded and owned by Jack DangermondReleased ArcInfo in 1971, the first commercial vector-base

2、d GIS systemThree main modules ArcMap for map production and analysisArcCatalog for data managementArcToolbox contains all the tools in ArcMap and ArcCatalog, plus many moreArcGIS Modules or ComponentsArcMap for map production and analysisArcCatalog for data managementArcToolbox contains all the too

3、ls in ArcMap and ArcCatalog, plus many moreEach has a different user interfaceThe Levels of ArcGISCosts more $sDoes moreArcView Map production and analysis ArcEditorData creationArcInfoHigh level analysisEach has the same user interface1/3/2008GISC 6382 Applied GIS Briggs UT-Dallas5Primarily carried

4、 out in ArcMap:via Selection/Select by Locationthis 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 Datageographic features are not themselves modifiedvia

5、 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

6、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 featuresvia ArcToolbox Generally these tools modify geographic feature, thus they create a new layer (e

7、.g. shape file)Tools are organized into multiple categoriesImplementing Spatial Analysis in ArcGIS 91/3/2008GISC 6382 Applied GIS Briggs UT-Dallas6DifferencesSelection: simply selects spatial featuresSpatial features are not modified.Selected features are highlighted on map and in the tableNo new ou

8、tput file saved unless you use Export/datajoins: 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 layers table from another layers tableAll geographic features ar

9、e “output” and no features are modifiedNo new output file saved unless you use Export/dataAnalysis 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.1/3/2008GISC

10、6382 Applied GIS Briggs UT-Dallas7Analysis Tools in ArcToolboxArcToolbox, particularly the Analysis Tools toolbox containsExtract toolset, includingClip 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, includingI

11、ntersect, which combines two polygon layers-with output limited to common areaUnion, which combines two polygon layers-with output covering full extent of both layersProximty toolset, includingBuffer, for creating buffer polygons at a specified distance around points, lines or polygonsPoint Distance

12、, for calculating distances between points within a specified radiusStatistics toolset, includingFrequency, which gives you counts of attribute value combinationsSummary Statistics, which gives you summary descriptive statistics for columns in a table, including sum, mean, min, max, etc.Tools useful

13、 for analysis of vector data are located in other toolsets as well! For example: Data Management ToolsGeneralization, containsDissolve, which removes boundaries between polgyons ObjectiveThe objective of the research is to answer the question: Are certain groups (the poor, or racial and ethnic minor

14、ities) more exposed to pollution than the population as a whole? Method 1: all schoolsWe have data for Dallas, TX on:Toxic emission sitesDemographic characteristics of schools We will create a 1 mile buffer around each toxic siteWe will compare the demographic characteristics of schools within the b

15、uffer to those outside the buffer Hypothesis 1Null Hypothesis: there will be the same percentage for each demographic group beyond and within the bufferAlternative hypotheses: there will be a higher percentage of Black, Low e, Hispanic, and Asian students, and a lower percentage of white students wi

16、thin the buffer.Method 2: schools within buffer onlyWe have data for Dallas, TX on:Toxic emission sitesDemographic 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

17、 the demographic characteristics of the ten (10) schools with the highest scores to the rest of the schools within the buffer.Hypothesis 2Null Hypothesis: there will be the same percentage for each group in the Top Ten schools compared with the rest of the buffer schoolsAlternative hypotheses: there

18、 will be a higher percentage of Black, Low e, Hispanic, and Asian students and a lower percentage of white students in the Top Ten toxic schools.1. Bring in the data files (C:UsersbriggsDocumentschinalecturesproject-armapdata)Dal_toxic_SPCS,shp contains the toxic sites and their toxicity scoresDal_s

19、chool_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

20、 mile of toxic sites- use SelectionSelect by location to select all schools within distance of 1 mile (5280 feet) from Dal_toxic-select features from Dal_school-that “are within distance”-Dal_toxic_SPCS-add variable (e.g called buffer) to Dal_schools and code for inside(=1) and outside (=0) -open at

21、tribute table for Dal_school-click Options and Add Field (short integer) called Buffer-right click column heading for buffer field (Dal_school_SPCS.buffer)-select Field Calculator-calculate Dal_school_SPCS.buffer = 1-be sure there is a in Calculate selected records only-Clear Selected Features after

22、 doing this (important!)3. Obtain student count totals within and beyond buffer.-Join Dal_school_SPCS layer with Dal_sch_stats table -right click on Dal_school_SPCS and select Joins and RelatesJoin- Box 1 ORG_NUM (for Dal_school_SPCS)-Box 2 Dal_sch_stats-Box 3 CAMPUS (for Dal_sch_stats in Box 2) -op

23、en the attribute table for Dal_school_SPCS -be sure join it is correct!-click on heading for Dal_school_SPCS.buffer,select Summarize and Sum the six Dal_sch_stats demographic fields(Dal.sch.stats.CPETALLC, CPETBLAC, CPETECOC, CPETHISC, CPETPACC, CPETWHIC)-click expansion box, then check SUM -name th

24、e output table Sum_buffer: - the output table should have two rows-1= within buffer-0= outside buffer -it is saved as .dbf file which can be read by Excel4. Use Excel to open Sum_buffer.dbf and calculate the percentages for within and beyond buffer-you may need to close ArcMap-you should calculate p

25、ercentages relative to total within buffer and beyond buffer-this is the row sum given by the variable Sum_CPETALNull Hypothesis: there will be the same percentage for each group beyond and within the bufferAlternative hypotheses: there will be a higher percentage of Black, Low e, Hispanic, and Asia

26、n students and a lower percentage of white students within the buffer.bufferCountTotalBlack-AfAmLow eHispanicAsianWhiteBeyond (0)378 270,742 79,994 143,326 102,226 10,304 77,020 Within (1)95 61,750 11,948 38,428 33,199 2,328 13,997 Percentages relative to total within and total beyond (row sum)beyon

27、d29.552.937.83.828.4within19.362.253.83.822.7Supports hypothesis?NoYesYesNoYes5. We need to calculate a toxicity score for each school based on distance to toxic sites and the toxicity score of the site. The ArcToolbox tool called POINTDISTANCE will calculate distance to all points within a given ra

28、dius. However, it is only available in ArcInfothe “top level” version of ArcGIS.To run POINTDISTANCE (if you have ArcInfo), go to ArcToolboxAnalysisProximityInput features: dal_schoolsNear features: dal_toxOutput table: sch_tox_disSearch radius: 5280 feetThe sch_tox_dis table is available in the dat

29、a folder if you do not have ArcInfo.6. Add sch_tox_dis.dbf table to ArcMap and open it (right click on layer name and select Open)-INPUT_FID is the feature identification (ID) number for schools -NEAR_FID is the ID for toxic sites within 1 mile (5280 feet) of a schoolSort by INPUT_FID (right click c

30、olumn name and select Sort Ascending)-note how some schools are listed multiple times (e.g. #5)-there are multiple toxic site within 1 mile Right click on sch_tox_dis (join table) and join with dal_Tox_spcs (target table) using: Box 1 Near_ID Box 2 dal_Toxix_SPCS Box 3 FID This adds toxic scores for

31、 each toxic site tosch_tox_dis table. It is a “one to many” join7. Weight toxic score by distance from school to toxic site. Add variable (field): Open table, click Options and then Add Field Score_dist as type Float (Floating point)-its added “in the middle” of the columns as sch_tox_di.Score_Dist

32、To calculate values: right click on this name and select Field Calculator Yes, to calculate outside an edit session.Build the expression:sch_tox_dis.Score_Dist =Dal_toxic.SCORE / sch_tox_dis.DISTANCERemove join by right clicking on table name (dal_tox_SPCS) and select Joins-Table has 5 variables and

33、 135 observations (OID 0-134)8. Aggregate observations in sch_tox_dis table by schoolSort sch_tox_dist. by INPUT_FID (schools) to see need for aggregation by school (multiple toxic sites per schoolnote #5 and #34)Right click on Score_dist column heading and select Summarize1. Field to summarize: INP

34、UT_FID (school) 2. Summary statistics Click expansion box for Score_dis and select SUM3, Output table is: sch_tox_scoreOutput table has four variables and 95 observations (rows): OID, INPUT_FID (school ID), frequency count, sum-score_dis9. Identify “Top 10” schools with highest toxicity scores Find

35、top ten:-Open sch_tox_score table-right click on the heading Sum_Score_Dist and select Sort Descending-select the top 10 schools by dragging mouse pointer down the grey boxes on the left side of the table (selected rows are highlighted in blue)Create variable to identify Top 10: -open the sch_tox_sc

36、ore table (if not already open)-click Options (at bottom of table) and Add Field (type: short integer) called TopTen-click column heading for TopTen -select Field Calculator-calculate TopTen = 1-Calculation is applied to the “selected fields” only10. Map the top 10 toxic schools using Proportional S

37、ymbols.Join sch_tox_score with spatial layer:(sch_tox_score is a table and not a spatial layer. We must first join it to the original school layer (dal_school_SPCS) for mapping.)Right-click on dal_school_SPCS and select Joins and RelatesJoin Box 1 Dal_school_SPCS_FIDBox 2 sch_tox_scoreBox 3 INPUT_FID Important: In the Join Options box, check This will keep only the schools within the 1 mile bufferMap the schools:Right click Dal_school_SPCS and