Screen Sharing: http://mit.webex.com/meet/jf

Key Ideas in Lab #4:  (Mapping and charting population density in Mass)

1. Review of assignment due dates:
• Lab #3 due today and Homework #2 is now online
• Lab #4 (today) is due next Monday (March 11)
• Hwk #2 part 1 due Wed. March 13
• Lab #5 (vector analysis) next Monday is due Wed. March 20
• In-class (open book) test on Monday March 18
• Hwk #2 part 2 due Friday. March 22
• END OF 11.205 (Friday, March 23) 
• <--- Spring Break --->
• Very preliminary project topic idea due Monday, April 1
• Lab #6 (raster analysis) on Mon. April 1  and due April 8
• This lab #6 and the rest are required ONLY for 11.188 and 11.520
• Lab #7 (GIS data gathering) on Mon. April 9 and due Mon. April 23
• Hwk #3 part 1 due Wed. April 17
• Hwk #3 part 2 due Wed. April 24 (last homework)
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 #4: (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
5. Open 11.188_lab2_web.mxd and copy web services into your Lab #5 document if you want to use the ESRI and MassGIS web services
6. Moving tables from ArcGIS into MS-Access

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