2. • Mapping helps us make sense of how we
relate to the world around us
• They are socially constructed perspectives on
• Maps reflect a tension between scientific
objectivity and subjectivity.
• Maps are not reflections of reality. They are
selections of reality.
• External controls (e.g. the purpose of a map
and who creates it)
• Internal rules (e.g. science and technology of
• Regulation of access to knowledge (who
decides what is mapped and why?)
4. Digital mapping
• Digital technologies democratize mapping:
that is, those of us who are not trained
geographers or cartographers can create and
5. We can
• Make experimental maps
• Visualize change over time
• Bring different kinds of information together
in a spatial framework to compare and
• Let’s look at some sample uses of digital
• Georectification is the process of layering
historical maps from different points in time.
• Georectification helps us see change over
• It’s accomplished, in part, by matching
latitude/longitude), and then warping the
layers so that they correspond to each other
as much as possible.
7. Mapping sites
• Here’s David Rumsey’s georectified map of
On Google Earth and
Check out more David Rumsey georectified
maps here: http://rumsey.geogarage.com/
Visit and experiment with the New York Public
Library map warper.
8. Thematic maps
• Thematic maps are data maps. That is, they
focus on mapping specific kinds of
information, e.g. social, political, economic,
• Census data is a common source of thematic
• Bubble maps and chloropleth maps are
frequently used to present thematic data.
9. • Each map representation requires different kinds
• A bubble map presents circles (bubbles) with
sizes in proportion to the associated data.
• You need boundaries—that is, clear geographic
• You need data specific to those boundaries.
• Look at Mike Bostok’s bubble map of US
population by counties. (next slide). What works?
11. Chloropleth Maps
• Chloropleth maps need boundaries as well.
• The group data into classes and then show
variations using color, patterns, or shades of
gray and black.
• The two following representations of White,
non-Hispanic population in the US show
different levels of granularity in analyzing
13. In this map, data was broken down to the county level, giving a more substantial
indication of population dispersion than the first map.
14. Aggregation maps
• Aggregation maps display large bodies of data
in depth, so that a single data point reveals
multiple layers of information. It helps users
browse through vast amounts of spatially-linked
information in manageable chunks.
• See Histories of the National Mall.
15. Animated Maps
• Good for showing change over time.
• Here’s an animated map of Hispanic
population change in Los Angeles County
16. Interactive Maps
• Interactive maps are often used for data
• With Geocoding, you can create maps using
the coordinates of a particular place.
• We’ll be doing this with Google Maps Lite—
we’ll be adding historic data to contemporary
18. Riot Maps
• 1968 Washington DC.
Evaluate these two maps. How do they present a
narrative? The Ferguson map was a crowdsourced on-the-
spot creation. How would you change or reorder
the information the data points include?