GIS Analysis for Public Health: �Sample Projects and Methods�
1737 Cambridge St. CGIS Knafel building Concourse level
Presentation for students in GHP 534: Introduction to Spatial Methods for Public Health
By Jeff Blossom, Center for Geographic Analysis (CGA), Harvard University
May, 2026
Image sources:
World Atlas: https://www.worldatlas.com/articles/which-countries-border-lesotho.html
Google Street View https://www.google.com/maps/@-29.8411419,28.0530202,3a,75y,128.27h,74.36t/data=!3m6!1e1!3m4!1sG5DCNyOy1zHAGSJdPwizMQ!2e0!7i13312!8i6656
Research Question:
What percent of Lesotho’s total population has access to a health facility?
Access defined as < 3 hour walk
What percent of Lesotho’s total population has access to a health facility?
Input data (all publicly available sources)
Elevation – For slope creation to estimate walking speed.
Trails, roads, rivers, bridges - OpenStreetMap.
Land Cover – European Space Agency
Population – WorldPop (U. of Southampton, U.K.)
Health Centers – Ministry of Health, Lesotho.
GIS Analysis Methods
ESA land cover classifications with travel coefficients.
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GIS Analysis
What percent of total population has access to a health facility?
Access is defined as within a 1 hour walk to a health facility in urban areas; within a 3 hour walk in rural areas.
78% of the population has access
GIS Analysis
What percent of total population has access to a health facility?
Access is defined as within a 1 hour walk to a health facility in urban areas; within a 3 hour walk in rural areas.
By adding 50 new health facility locations based on the GIS analysis to the model, 90% of the population has access.
PRISM data example – one day, one variable
Conclusions: We found that greater short-term precipitation may trigger airway inflammation in adolescents, particularly among those with asthma.
Link to American Thoracic Journal publication:
https://www.atsjournals.org/doi/abs/10.1513/AnnalsATS.202209-805OC
Link to the code used, ISPRS publication, and FOSS4G presentation: https://gis.harvard.edu/high-performance-computing-address-level-climate-data-extraction
Case 3: Visual Analysis / Cartography
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Artificial Intelligence (AI) in GIS
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��https://www.google.com/search?q=language+learning+models ��https://www.ontotext.com/knowledgehub/fundamentals/what-is-a-large-language-model/
Language Learning Models (LLM)
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GeoAI
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GeoAI tools in ArcGIS Pro
ChatGPT can be produced to generate geographic data. If you use ChatGPT for data or informational purposes, make sure to cite it. ��
Leaflet HTML code created from ChatGPT answering “map the last 10 superbowl venues”
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Jan. 2024�Question to ChatGPT with DALL-E: “Please make a map of Texas with Cities, Rivers, Counties” ��Result 🡪�not great.
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May, 2025�Question to ChatGPT with DALL-E: “Please make a map of Texas with Cities, Rivers, Counties” ��Result 🡪�pretty close to the real thing.
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May, 2026�Question to ChatGPT with DALL-E: “Please make a map of Texas with Cities, Rivers, Counties” ��Result 🡪�pretty close to the real thing.
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May, 2026�Question to Claude, Sonnet 4.6: “Please make a map of Texas with Cities, Rivers, Counties” ��Result 🡪�only cities!
Explore your data with interactive Dashboards in ArcGIS Online
May, 2026�Question to Claude, Sonnet 4.6: “Can you make a line chart with county_name on the horizontal, population on the vertical axis, with all of the 'contains' fields available as filter toggles, and the ability to sort by population with the attached data”
Attached data, in .csv format:
This produced an interactive chart in html format. Download the html at this link and open on your computer to check it out.
May, 2026�Question to Claude, Sonnet 4.6: “Can you make a line chart with county_name on the horizontal, population on the vertical axis, with all of the 'contains' fields available as filter toggles, and the ability to sort by population with the attached data”
A recent project: Mapping riverine villages in Amazonas, Brazil
Challenge: Converting ~150 community location coordinates from a poor quality PDF. Manually entering this into a spreadsheet is tedious and subject to data entry error.
Optical character recognition is needed, but did not work on this PDF in Adobe Acrobat or Illustrator.
Solution: Taking screenshots of the PDF like the one above, and loading these .jpg images into ChatGPT 5 with the prompt “please convert to .csv format with village, lat, long, in decimal degree format”.
Result: A file like this, ready for mapping:
Manually checking a sample of these locations against
modern base maps confirmed their accuracy.
The resulting map focused on showing just 6 of these locations, and was designed with simplicity in mind
AI for Geo
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AI for Geo
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GeoAI example
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GeoAI example
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Give a score from 1 to 10 for the Safety, Greenery, Cleanliness and Walkability, in this image, and provide a short reason for each.
Current work in development by Lingbo Liu and others, Harvard CGA
AI for Geo �With increasing data collection (both temporally and topically) from Earth observation and human observation sensors, Geo-AI is essential for computation and the metamorphosis of turning data into useful, timely information.��Much of what humans know and do can be loaded into an LLM. How the AI can be best utilized is a more important challenge to solve.
AI is becoming better and better at interactive data visualization, but still struggles with geo-mapping.
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Training at the CGA
Training at the CGA
One more workshop this spring…
Thank You!
Jeff Blossom
See more CGA projects: https://gis.harvard.edu/research-portfolio
CGA website: http://gis.harvard.edu/
CGA staff email addresses: https://gis.harvard.edu/teams
CGA general contact: http://gis.harvard.edu/contactus �
Center for Geographic Analysis (CGA)
CGA People
CGA Core Services
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Instructional Programs
GIS Site Licenses
Web GIS & Hosted Mapping
Fusion Tables
Research Consultation
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Venues of the 2012 London Olympics
CGA Service Projects: Maps and Visualization
Land cover of Gujarat province, India
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The “Out of Eden Walk” project
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Visualizing Paul’s GPS data on a web map
Visualizing Paul’s GPS data in 3D
Geographic storytelling with Story Maps
More on the Out of Eden Walk: https://gis.harvard.edu/out-eden-walk
See more CGA projects on our portfolio site