Saturday, May 10, 2014

Mapping London's Cholera Outbreak


Sooner or later all online mapping platforms must be used to recreate John Snow's 1854 dot map of cholera deaths in London's Soho.

Snow plotted the deaths caused by cholera around Broad Street in Soho and the location of eleven water pumps used by the locals. The distribution of the dots helped Snow discover that cholera occurred most frequently among those who drank from the Broad Street water pump.

Snow's map helped to disprove the then popular theory that diseases such as cholera and bubonic plague were air borne and spread by 'bad air'. These days John Snow's map seems to be most used by neo-geographers to test the capabilities of online mapping platforms.

This Esri map of John Snow's Map is a nice example of how John Snow's data can be used as data layers on a digital map. John Snow's Map uses an overlay of Snow's original map as one layer. The locations of the water pumps are available in another layer and the locations of the recorded deaths has been added as yet another layer.

For good measure the map's creator has also added a Flickr layer to the map so that you can view photos of the John Snow pub, the Broad Street water pump and the John Snow plaque on Broad Street.

If you want to create your own version of John Snow's map then you can grab the data in a number of formats from Robin's Blog. Robin's Blog has geo-coded the locations of the water pumps and cholera deaths and provides options to download the data as raster files, KML files or in a Google Fusion Table.
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