1. Digital spatial history

2. • Mapping helps us make sense of how we
relate to the world around us
• They are socially constructed perspectives on
the world
• Maps reflect a tension between scientific
objectivity and subjectivity.
• Maps are not reflections of reality. They are
selections of reality.

3. Influences
• External controls (e.g. the purpose of a map
and who creates it)
• Internal rules (e.g. science and technology of
mapmaking)
• 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
annotate maps.

5. We can
• Make experimental maps
• Visualize change over time
• Bring different kinds of information together
in a spatial framework to compare and
contrast
• Let’s look at some sample uses of digital
mapping technologies.

6. Georectification
• Georectification is the process of layering
historical maps from different points in time.
• Georectification helps us see change over
time.
• It’s accomplished, in part, by matching
coordinates (georeferencing
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
Chicago 1857.
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,
agricultural statistics.
• Census data is a common source of thematic
maps.
• Bubble maps and chloropleth maps are
frequently used to present thematic data.

9. • Each map representation requires different kinds
of information.
• A bubble map presents circles (bubbles) with
sizes in proportion to the associated data.
• You need boundaries—that is, clear geographic
coordinates
• You need data specific to those boundaries.
• Look at Mike Bostok’s bubble map of US
population by counties. (next slide). What works?
What doesn’t?

10. • Mike Bostock created a bubble map of US
population by county.

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
data.

12. In this map, data was analyzed on the state level.

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
1940-2000

16. Interactive Maps
• Interactive maps are often used for data
exploration
• http://www.nytimes.com/interactive/2014/04
/23/upshot/24-upshot-baseball.
html?abt=0002&abg=0

17. Geocoding
• 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
maps.

18. Riot Maps
• 1968 Washington DC.
http://www.washingtonpost.com/wp-srv/
metro/specials/mlk40/map/
2014 Ferguson
https://mapsengine.google.com/map/embed?mid=zQ
XCU9jTCWt8.k_AxWZwk4ODM
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?