This document summarizes a project to recreate Dr. John Snow's 1854 "Ghost Map" of the London cholera epidemic using GIS. The project analyzed the epidemic's spread and tested the hypothesis that cholera is waterborne by geocoding pump locations and cholera deaths. Results from raster, vector, and geostatistical analyses all showed highest death densities around the Broad Street pump, supporting Snow's conclusion that contaminated water from this pump spread cholera in the Soho neighborhood. The geostatistical analysis identifying the mean center of deaths was deemed the most compelling presentation of Snow's findings, showing spatial correlation between the Broad Street pump and cholera cases.

1. Executive Summery
Lidia Roy for GISC 2420 on September 12, 2018
The goal of the project is to recreate, analyze and present the Ghost Map utilizing GIS. In 1854
Dr. John Snow mapped the cholera epidemic, that spread out in London SOHO neighborhood.
The two theories which raised the question about exact cause of the disease - 1.the Contagion
theory (that some kind of agent passed between cholera victims) and the 2. Miasma theory (that
bad odors emanating from certain environments, caused cholera). So, the question came as per
miasma theory, if it is airborne then why had some buildings in the SOHO neighborhood been
almost out of cholera threat? Why not to other cities or areas? Dr. John Snow with his
assistance Reverend Henry Whitehead collected data to support their contagion theory and was
able to convince the officials that the cholera is a waterborne disease, which spread through the
Broad Street water pump. John Snow had performed his analysis only with pen and paper, but
here we have created a Raster, Vector and Geostatistical map to recreate, analyze and present
the ghost Map utilizing modern GIS.
To create a raster, vector and statistical analysis, I downloaded and extracted the data from my
course of work, then I created the metadata by exploring the project. To recreate and analyzing
the original Ghost Map, I needed to geocode the pumps and georeferenced the Ghost Map to
locate the pumps. To find out the number of cholera deaths and occurrence on which street, I
geocoded the deaths and then analyze the death by street using summarized table by a basic
statistical analysis.
Now to determine if there is a spatial connection between Broad Street Pump and 1854 London
Cholera Epidemic, firstly I visually analyzed the cholera fatalities using symbology. To quantify
the analysis, I had created theissen polygons to show the proximity of household fatalities to
each public water pump in the area and used spatial join to allocate to deaths for each location
using vector analysis.
To perform a raster analysis by calculating the density of cholera facilities, that highlights those
areas where facilities were more common. The kernel density tool calculated the number of
deaths per hectare.
Lastly, I calculated the standard deviational ellipse and mean of the deaths by using
geostatistical analysis to identify the mean geographic Center of the deaths.
After performing all the analysis, the results show that the water supply of the Broad Street
pump and the Cholera epidemic are correlated. In Raster, Vector and Geostatistical analysis the
Broad Street Pump area shows the highest death density. I believe the Geostatistical analysis is
the most compelling way to present the case of the cholera epidemic in SOHO neighborhood in
London as it showed the center of the total deaths. John snow realized this and presented his
analysis in an effort to convince the St. James Parish Board of governors to remove the handle
from the Broad Street Pump.