API-231 / GIS-PubPol / Meeting 00 (GIS 101)
Yuri M. Zhukov
Visiting Associate Professor of Public Policy
Harvard Kennedy School
January 22, 2024
Welcome to API-231!
What is GIS?
What are Geographic Information Systems?
- tools for collection, maintenance, storage, analysis, visualization, distribution of geospatial data
- a.k.a. “geospatial data science”
Policy applications
- GIS help us understand
- where social, economic, public health problems occur
- who is affected by them
- how to monitor, manage and mitigate them
Scientific applications
- GIS help us
- acquire data
- test hypotheses
- make forecasts and predictions
History of geospatial data analysis / Public health
The blue wraith
In 1854, there was an outbreak of Cholera in London’s Soho district.
It killed 616 people.
The blue death
Cholera is an infectious disease of the small intestine.
It causes severe dehydration in its victims. It is quite deadly.
The experts
The Board of Health struggled to find the epidemic’s cause.
The scapegoats
The leading theory was that Cholera was caused by foul air and poor hygiene.
The geospatial data science
Dr. John Snow believed that Cholera was spread by contaminated water, not foul air. To test his theory, he created a map of Cholera cases at each address in Soho.
The pump
He found a cluster of cases around a water pump on Broad St.
The public health campaign
He told authorities to break pump’s handle so people couldn’t draw water from it.
Data scientist has policy impact
Cholera cases drop in Soho, supporting Snow’s theory about contaminated water.
History of geospatial data analysis / Military intelligence
A new weapon
During WWII, Germany launched 1,358 V-2 Rockets at London.
No way to intercept, no way to defend
V-2’s speed and trajectory made it invulnerable to anti-aircraft guns and fighter jets.
Terror rains from the sky
V-2 strikes kill 2,724 people in UK + 6,000 civilians and military across Europe.
(+ $~$15,000 concentration camp prisoners died constructing the V-2)
Locations of V-2 strikes in London
Bomb damage maps were interpreted by some analysts as showing that impact sites were clustered. This suggested the V-2’s guidance system was more sophisticated than intel estimates thought. Allies tried to jam V-2’s guidance system, to no effect.
Wartime geostatistics
R.D. Clarke applied a statistical test to assess whether any hard evidence could be found for clustering. For each square, Clark recorded the total number of observed bomb hits (537 total in study area), and number of squares with \(k=1,2,3,\dots\) hits.
Poisson cumulative density function
Clarke derived the expected number of squares with \(k\) hits from the cumulative density function of the Poisson distribution \(\sum_{k=1}^{n}\frac{e^{-\lambda}\lambda^{k}}{k!}\), with \(\lambda=\frac{537}{576}\) and \(n=576\).
| No. of bombs per square | Expected | Observed |
|---|---|---|
| 1 | 226.74 | 229 |
| 2 | 211.39 | 211 |
| 3 | 98.54 | 93 |
| 4 | 7.14 | 7 |
| 5+ | 1.57 | 1 |
The distribution of observed V-2 strikes conformed quite closely to the Poisson distribution (\(\chi^{2}=1.17, p=0.88\)). If strikes were clustered, we would have seen many more squares with a high number of bombs.
Conclusion: V-2 impact sites were random, not clustered.
Rocket strikes were indiscriminate (within city of London), not targeted.
Contemporary uses of geospatial data analysis
Example: Track violence in the Russia-Ukraine War
Example: Provide situational awareness during military operations
Example: Provide real-time information for emergency management
Example: Analyze residential segregation in American cities
