1. An Exploration of using Nighttime Satellite Imagery from the DMSP OLS for Mapping Population and Wealth in Guatemala Paul C.Sutton psutton@du.edu Department of Geography University of Denver

2. Outline Motivation: Why do this? Is is worthwhile? Brief Summary of DMSP OLS image processing How Nighttime images can be used to map urban areas and estimate urban populations. How Nighttime images can be used to estimate and map economic activity How Nighttime images may be used to estimate Human Impact on the environment

3. Why Use Nighttime Imagery to Map/Model Demographic and Socio-Economic Phenomena? Social, Economic, and Behavioral Demographic Data are the major gaps to be filled in globally integrated geo- information Existing Information is degrading due to increasing human mobility, and the fact that a growing proportion of the earth’s population live in developing countries which can’t afford to conduct accurate censuses Spatially referenced demographic information is a vital component of studies of: Hazard Planning and Response, Sustainability and Development Issues, and countless other cross-disciplinary investigations

4. Two sun-synchronous polar orbiting satellites (865 km orbit) Observations at 1) ~ Dawn & Dusk, 2) ~ Noon & Midnight Pixel Size: smoothed ~2.4 km 2, fine ~ 0.5 km 2, Swath Width ~3000 km Two Bands: 1) Panchromatic VNIR, 2) Thermal Infrared Dynamic Range: VNIR more than 4 orders of magnitude larger than traditional sensors optimized for daytime observation (e.g. sees light from reflected moonlight to reflected sunlight) Data available from early 1970’s to Present, Digital Archive est. in 1992 Data Products derived from imagery (hyper-temporal mosaicing): % cloud cover, % light observed, Fires, Lantern Fishing, Gas Flares, City Lights, Radiance Calibrated City Lights, Atmospherically corrected radiance calibrated city lights System Overview Defense Meteorological Satellite Program Operational LineScan System (DMSP OLS)

5. Example of Cloud Screening over Italy VNIR over Italy Thermal over Italy

6. A comment on aggregation & scale: This is a 1 km 2 pixel in Denver, Colorado

7. Nighttime Satellite Imagery

8. Fires, Fishing, Flares, & City Lights Lantern Fishing In Japan City Lights along the Nile Forest fires in Australia Gas Flares in the Persian Gulf

9. Mapping Population Ln(area) vs. Ln(pop) regression method for Estimating the Population of Urban Clusters Intra-Urban measures of population density: Light Intensity as a proxy for Population Density Works better in countries with high % of population in urban areas. Rural Electrification in Guatemala probably reduces utility of these methods.

10. Light Intensity from DMSP OLS imagery matched with Photographs using GPS

11. Night Lights and Pop Den in Guatemala

12. Mapping Economic Activity and GDP per Capita Just as Night Lights are a proxy measure of population they are also a proxy measure of Economic Activity. Again, relationship is far from perfect (see next slide); however, Light intensity can be used as a proxy measure of GDP. GDP of Guatemala ~50 Billion; 25% apportioned to dark area to account for agriculture, remaining 75% apportioned based on light intensity. Using LandScan Population Density dataset and dividing it into this map of GDP produces a map of GDP per Capita.

13. Scatterplot of Night Light Energy & PPP of GDP for 208 nations

14. Global map of Marketed Economic Activity as measured by Nighttime Satellite Image Proxy

15. Dividing ‘map’ of GDP from DMSP by Pop Density from Landscan

16. Using Nighttime Imagery to Create an “Environmental Sustainability Index” Measure Environmental Endowment of Nations using Ecosystem Service Value of Nation’s Lands Measure Human Impact of Nation from DMSP OLS nighttime Image Divide The above measures to create and ESI (Environmental Sustainability Index)

17. Measuring Human ‘Impact’ What data can be used in the I = P*A*T formulation? If you use Population for P, GDP/Capita for Affluence, and CO 2 Emissions/GDP for Technology, then ‘Impact’ simplifies to total CO 2 emissions Daily & Ehrlich used Energy Consumption per Capita to capture the A*T “Impact” is a function of both population size and individual consumption levels Nighttime Imagery from the DMSP OLS correlates with Population, Energy Consumption, CO 2 emissions, and GDP and may be the best spatially explicit, single variable, measure of ‘Impact’

18. Ecosystem Service Valuation: IGBP to Nature Conversion Table

19. Global map of ‘Non-Market’ economic activity from ecosystem services

20. Deriving The Eco-Value / Night Light Energy Environmental Sustainability Index This index is similar to the inverse of population density e.g. ‘square kilometers of land per person’ However; ‘square kilometers of land’ is adjusted by the land’s ecosystem service value; and, ‘per person’ is measured by the nighttime satellite imagery provided by the DMSP OLS

21. A representation of the datasets used to calculate Eco-Value and Impact from around Central America

22. Conclusions DMSP OLS nighttime imagery shows a great deal of promise for myriad applications such as population estimation, mapping of economic activity, and measuring human impact on the environment. More Validation and fine tuning of models is needed. Issues of spatial scale of measurement still problematic.