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Key Ideas in Lab #3:  (Mapping and charting population density in Mass)

1. Review of assignment due dates:
• Lab #2 due today and Homework #1 is due next Monday (February 24)
• Lab #3 (today's lab) is due next Wednesday (February 26)
2. Mapping population density with too-detailed a map -- 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'
3. Constructing meaningful indices (such as population density)
   • Requires excluding cases and normalizing data
   • May require creation of new features and attributes in writeable directories.
4. Charts and business graphics in ArcMap
   • Another useful dimension: business graphics
   • Careful about which data gets mapped
     • Understand the one-to-many linkages among tables
     • Be aware of selected sets in maps and tables - most operations act on selected sets and you may forget about the selections
5. Handling one-to-many relationships in MS-Access
   • Equivalent to 'summarize' command for ArcMap attribute tables (but more powerful)
   • Need to activate '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 #3: (Data manipulation in ArcGIS)

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
   • You will want to 'summarize' by town name before charting
   • Be careful about which table to join to maps (i.e., the one-row-per-town table after summarization)
   • Selecting on the map can impact chart as well as highlighting attribute table rows (if correct tab has been checked)
4. Copying web services into ArcMap from earlier ArcMap documents
• Double-click on 11.188_lab2_web.mxd in the class data locker and then drag-and-drop web services into your Lab #3 ArcMap session.
5. Open 11.188_lab2_web.mxd and copy web services into your Lab #3 document if you want to use the ESRI and MassGIS web services
6. Moving tables from ArcGIS into MS-Access

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