Census Thematic Mapping

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Census Thematic Mapping

• Brianna Richards, Danielle Micale,
• Carrie Saylor

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Overview

• Create three thematic maps
• Each map must use different data themes
• One map must be created using Decennial Census
• One map must be created using the American
  Community Survey
• Two maps must have the same area and correlating
  themes so they can be compared

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Purpose of Thematic Maps

• To illustrate the geographic distribution of one
  particular attribute or the relationship between
  a few selected attributes
• Made for a single intended purpose, unlike
  reference maps which are more general
• Useful in transforming geographic data into
  geographic information because thematic mapping
  can reveal spatial patterns that arent portrayed
  by data sets

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Thematic Map Example
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Types of Thematic Maps

• Dot Density Map
• Represents the distribution of a certain
  attribute through an arrangement of dots.
• Each dot represents a specified amount of the
  attribute.

• Proportional Symbol Map
• Represents the distribution of an attribute with
  a specific symbol.
• The size of the symbol varies directly with the
  amount of the attribute being represented.

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Choropleth Map

• Geographic areas are colored in shades that
  represent specific amounts of the attribute being
  displayed.
• Benefit- it is possible to accurately represent
  location.

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Data Classifications

• The purpose of data classifications are to
  arrange entities with similar properties into
  groups.
• On a thematic map the different groups are
  represented by different symbols.
• In this way data classification makes thematic
  maps easier to interpret.

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Data Classes Equal Interval

• The intervals in this classification are the same
  size, but do not necessarily have an equal
  distribution of data points.
• Class One 1-10
• Class Two 11-20
• Class Three 21-30
• Class Four 31-40

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Data Classes Quantile

• The intervals in this classification contain an
  equal number of data points, but the intervals
  vary in size.
• Class One 1-4
• Class Two 5-15
• Class Three 16-18
• Class Four 19-23

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Data Classes Natural Breaks

• This classification divides the data points into
  groups that naturally appear.
• Think of the in-class project.

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Instructions

• Go to http//factfinder.census.gov
• Place your mouse over Maps (on the left side of
  the screen) and click Thematic Map
• Click on the theme of your choice (under the
  categories of People, Housing, and Business and
  Government).
• Once the map is displayed click on Data Classes
  on the upper left side of the screen.

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• Click the Boundaries tab.
• There should be a scroll bar beneath the words
  Choose a survey instance. Click on this and
  select 2005 American Community Survey.
• Click the Classes tab and select a Classing
  method. These should be changed for each map.
• Select Update.
• Select Print/Download at the top of the screen.
• Click Download.
• Select Download the Map and Legend in PDF Format
  at the bottom of the screen.

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• Save the map, then open.
• Do a screen capture by pressing the AltPrint
  Screen keys.
• Save this picture and import it into Frontpage.
• Repeat the above steps while varying the themes
  and the data source.
• At least one data source should be from the
  American Community Census and one from the
  Decennial Census.
• Try to make at least two of the maps with themes
  can could be related (ex poverty levels and high
  school education).
• You should also vary the Classing method with
  each map (ex Natural Breaks).

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• When you are finished with all three of your
  maps, do a comparison of two of them that are of
  the same area and similar themes. Do you notice a
  trend between the two themes? Why do you think
  this trend exists?
• Make sure to include a list of the sources you
  used at the end of your project.

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Sources

• DiBiase, David (2002) Understanding Geographic
  Data. Module 6 Census Data. ESRI Virtual Campus
  http//training.esri.com Accessed April, 2007.
• United States Bureau of the Census (2002)
  American FactFinder. http//factfinder.census.gov
  Accessed April, 2007.

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Websites

• You can find these directions at
• dlm5029
• blr5033
• css5072