• Examine the location patterns of Cambridge stores by using the 'spatial join' tools to tag store location data (bookstores, ice cream shops, record stores) with the demographic characteristics of their neighborhood. (This is a 'point-in-polygon' operation.)
• Estimate the number of children living near Ames Street by:
  • Creating a buffer around Ames St.
  • Intersecting the Ames street buffer with the Cambridge blockgroup data
  • Apportioning children in each block group that is split by the buffer in proportion to the block group area in the buffer

Lab #5 Issues:

• Join-by-location is different from select-by-location. Joining actually moves attribute information across layers. Selecting only affects which features are displayed (and which features can subsequently be exported or operated upon).
• Join: no need to copy all attribute fields; can use the 'Fields' tab in layer properties to turn fields on/off for display and joining purposes.
• Buffering Ames St. is similar to previous buffering done on Mass Ave; but pay particular attention to the instructions on setting map and display units.
• Apportioning Cambridge children to the parts of each block group that falls within the buffer.
  • Union and Intersect operations retain the old polygon areas.
  • You need to compute the new-polygon areas after the buffer cuts the block groups into smaller sections.
  • The Field/Calculate-geometry option simplifies the area calculations.
    • But this lab shows you how to do it with Python code.
    • Using Python code allows access to the internal data model, which is a powerful key to building customized GIS apps.

General ArcMap Tips:

• Folder, shapefile, and table names:
  • Use only letters and numbers with NO spaces, special characters, etc.
  • Start all names with a letter.
• Save early and often:
  • Always have a recent unused copy of any MXD documents (the ArcMap document mymapfile.mxd).
  • Every time you start an ArcMap session from a saved document, save it right away into an mxd document with a new name (version2, ver3, or with the session's date).

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Last modified 2017- 2020 Joe Ferreira and Juan Camilo Osorio.