Image Processing Reference
If you use a DMSP OLS data product be appreciative of the work of literally
hundreds of people that were involved in the acquisition, storage, processing and
analysis of the imagery that has been 'packaged' for you. It is important to appreci-
ate these issues in order to make the most accurate and appropriate use of any
remotely sensed imagery.
Summary of Several Applications of the Nighttime
There are many myriad applications of the DMSP OLS imagery. A brief description
of several of them follows.
The city lights data product is clearly a measure of human activity on the planet
that is a complex combination of population density, cultural variability, and levels
of economic development. Fortuitously, the cultural variability and levels of eco-
nomic development are less variable within national boundaries. This allows for
interesting inter-national comparisons of the imagery. The nighttime imagery has
been used to delineate urban extent nationally in the United Sates (Imhoff et al.
1997 ). Clearly, this delineation of urban extent can be applied globally by changing the
light intensity threshold that defines 'urban'. This threshold
changes from nation to nation primarily because of the vary-
ing levels of economic development and varying cultural
practices associated with land use and energy consumption.
Utilization of the imagery to delineate urban extent allows
for the measurement of the areal extent of urban clusters and
estimation of their population. This has been done in China
(Lo 2001, 2002 ), the United States (Sutton et al. 1997 ), and
globally (Sutton et al. 2001). The spatially explicit nature of
the data has been used to compare the saturated areas of the
high-gain data to theoretical models of urban population
density (Sutton 1997 ). The DMSP OLS imagery has also
been used for classifying urban areas in the creation of finer resolution land-cover
datasets of the United States with Landsat data (Vogelmann et al. 2001 ).
Because nighttime imagery is a good proxy measure of population it is also a
good proxy measure of correlates of population such as economic activity and
energy consumption. Consequently the DMSP OLS imagery has been used to mea-
sure CO 2 emissions nationally (Elvidge et al. 1996 ; Doll et al. 2000 ) and to map
economic activity locally (Sutton and Costanza 2002 ). Variation in the light intensity
within urban areas has also been used to map the impervious surface of the conter-
minous United States (Elvidge et al. 2004 ) and map intra-urban 'ambient' population
density (Sutton et al. 2003 ). These applications of the DMSP OLS imagery take
advantage of the time of observation, spatially explicit nature of the data, and global
coverage of the DMSP OLS imagery. The following examples should enhance your
appreciation of how the DMSP OLS data products can be used.
city lights can be
used as a proxy
levels of economic