Digital spatial history

• 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.

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?)

Digital mapping

• Digital technologies democratize mapping: that is, those of us who are not trained geographers or cartographers can create and annotate maps.

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.

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 (georeferencinglatitude/longitude), and then warping the layers so that they correspond to each other as much as possible.

Mapping sites

• Here’s David Rumsey’s georectified map of Chicago 1857.

On Google Earth and

Check out more David Rumsey georectifiedmaps here: http://rumsey.geogarage.com/

Visit and experiment with the New York Public Library map warper.

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.

• 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?

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

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.

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

In this map, data was broken down to the county level, giving a more substantial indication of population dispersion than the first map.

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.

Animated Maps

• Good for showing change over time.

• Here’s an animated map of Hispanic population change in Los Angeles County 1940-2000

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

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.

Riot Maps

• 1968 Washington DC. http://www.washingtonpost.com/wp-srv/metro/specials/mlk40/map/

2014 Ferguson https://mapsengine.google.com/map/embed?mid=zQXCU9jTCWt8.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?