will continue to flow to NGDC until 2010 or 
even 2015. The nighttime low light imaging 
capabilities of the OLS will be continued in the 
combined DoD - NOAA polar orbiting 
meteorological satellite program (NPOES). 
We have developed algorithms for mapping 
fires, human settlements, and gas flares using 
time series of nighttime DMSP-OLS 
observations. NGDC is currently completing 
the first systematic global inventory of human 
settlements based on satellite observations. 
NGDC has completed a six year (1992-97) 
nightly inventory of fires in Madagascar for 
the U.S. AID using DMSP-OLS data. The core 
set of algorithms and details regarding the 
sensor and data characteristics are described in 
Elvidge et al. (1997a,b,c). Data products can 
be obtained at “Nighttime Lights of the World" 
(http://WWW .ngdc.noaa.gov:8080/production/ 
html/BIOMASS/night.html). 
NGDC is completing a global radiance 
calibrated map of human settlements using a 
times series of nighttime OLS observations 
from 1996-97. Imagery are only used from the 
darkest third of each lunar cycle to avoid 
problems with moonlight clouds and 
moonlight reflections of water bodies. 
3. RESULTS 
The radiance calibrated lights are produced in 
the 1 km equal area grid of the Interrupted 
Goode Homolosine Projection (IGHP), but are 
subsequently converted to a 30 arc second 
latitude-longitude grid. The time series data 
are analyzed to determine the percent 
frequency with which lights were observed in 
each grid cell within the set of cloud-free OLS 
observations. By normalizing for variation in 
the number of cloud-free observations, it is 
generally possible to distinguish between fixed 
light sources (cities and towns) from 
ephemeral events, such as fires. A frequency 
threshold of 6 to 10 % is applied, removing 
most fires and other ephemeral events. 
Manual editing is then used to complete the 
removal of fire detects in certain regions. 
Features include the lights from cities, towns, 
villages, industrial sites, fishing boats and gas 
flares. Field checking in the USA indicates 
that towns as small as 120-200 people can be 
detected. 
An example of lights derived for Europe are 
presented in Figure 1. As a final step in 
assembling a global map of human 
settlements, NGDC will edit the stable lights to 
remove gas flares, fishing boats and other 
features which are not associated with human 
settlements. 
The relation between area lit, derived from the 
DMSP-OLS radiance calibrated lights, 
population, economic activity, and electric 
power consumption are currently being 
investigated. A preliminary examination of 
the data indicates that the satellite radiances 
are highly correlated, in most countries, to 
these and other basic measures of human 
activity. 
4. CONCLUSION 
We report on progress towards the completion 
of a radiance calibrated global inventory of 
human settlements, derived from nighttime 
data from the Defense Meteorological 
Satellite Program (DMSP) Operational 
Linescan System (OLS). The DMSP-OLS has 
a unique capability to observe faint sources of 
visible - near infrared emissions present at the 
Earth’s surface, including cities, towns, 
villages, gas flares, and fires. NGDC receives 
global coverages of DMSP-OLS data in near 
real time and has developed algorithms for 
producing georeferenced fire and human 
settlements products. The global human 
settlement product is being assembled at 1 km 
resolution using a time series of DMSP-OLS 
observations spanning the 1996-97 time 
period. Data applications which are being 
explored include the spatial apportionment of 
human populations, fossil fuel trace gas 
emissions, urbanization impacts on food 
production, and urban heat island effects on 
meteorological records. 
5. REFERENCES 
Elvidge, C.D., Baugh, K.E, Kihn, EA, 
Kroehl, H.W, Davis, E.R, 1997a, Mapping of 
city lights using DMSP Operational Linescan 
System data. Photogrammetric Engineering 
and Remote Sensing, v. 63, p. 727-734. 
Elvidge, C.D., Baugh, K.E, Kihn, E.A, 
Kroehl, H.W, Davis, E.R, Davis, C., 1997b, 
Relation between satellite observed visible - 
near infrared emissions, population, and 
energy consumption. International Journal of 
Remote Sensing, v. 18, p. 1373-1379. 
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
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