Key Ideas in Lab #4:

1. Handling one-to-many relationships in ArcMap
   • Tricky to map population density when towns may have more than one part (polygon).
   • Common complication since geometry and data tables come from different sources
   • More common with detailed (large scale & small area) maps - Boston has more than one 'part'
2. Constructing meaningful indices:
   • Requires excluding cases and normalizing data
   • May require creation of new features and attributes in writeable directories.
3. Charts and business graphics in ArcMap
   • Another useful dimension: business graphics linked to selected sets in maps and tables
4. Handling one-to-many relationships in MS-Access
   • Equivalent to 'summarize' command for ArcMap attribute tables (but more powerful)
   • Need to turn on 'totals' row in the query builder GUI
   • 'Group by' the column(s) you want to collapse into one unique value per row
   • Specify an aggregation function for the other columns (count, sum, average, minimum, ...)

Key Techniques in Lab #4:

1. Joining attribute tables in ArcMap
• Identify matching columns for each table
• Direction matters! start with geographic table
• Join operation will ignore >1 match to any mapable row!
2. Summarizing ArcMap attribute tables:
• Aggregate/summarize all the other attributes for the rows that have the same value in the 'summarize' column
• Highlight the 'group by' column (where each unique value results in one output row)
• Select other columns that you wish to aggregate (via 'count,' 'sum,' 'max,' etc.)
3. Charting the correct table
   • May need to 'summarize' a table before charting
   • Be careful about which table to join to maps (i.e., the one-to-one table after summarization)
   • Selecting on map can impact chart as well as highlighting attribute table rows (if correct tab is checked)

Debriefing (about prior labs and homework):

1. Resetting ArcGIS configuration files (when your customzied ArcMap startup settings are screwed up):
   • user customizations are saved in H:\WinData\Application Data\ESRI
   • The ArcMap template file is: H:\WinData\Application Data\ESRI\ArcMap\Templates\normal.mxt
     
   • Phil Thompson (at CRON) suggests using these commands to erase the ESRI subdirectory (and related registry setting) in order to start fresh when restarting ArcGIS
     • Exit from ArcGIS apps and run these two commands in a ' command prompt' window:
     • reg delete hkcu\software\esri
     • rmdir /s /q "%APPDATA%\esri"
       
2. Debugging skills: Verify success of each step of many-step procedure:
   • If buffering: did you buffer all features or only a selected subset of features?
   • If adding columns, summarizing, calculating: do you have write-access to the feature shapefile?
3. Customizing layers:
   • Shapefiles (and coverages) on disk (or in SDE):
     • One 'shapefile' includes many separate files on disk to store all retained information (including projections, indices)
     • Need write access to change any one of them
   • Layers in ArcMap
     • Can view in different projection by setting active 'data frame' projection
     • Can exclude features (rows) via the 'definition query' tab in layer properties (in which case the excluded features are retained on disk but not used within ArcMap processing of that data layer)
     • Can choose to manipulate only 'selected features' or 'all features' with most operations
     • Can 'export' shapefile and/or table of selected features and visible attribute columns to writeable space
     • Can retain symbology and other settings by saving as 'layer' in personal geodatabase
     • Can have more than one 'copy' of the same shapefile (or coverage) in a data frame
4. Comments on Labs 1 and 2: Follow this link for comments and sample maps for Labs 1 and 2:
   

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