Technical Background
Under dark sky conditions, the use of night vision goggles (NVG) allows military personnel
to view objects up to 984 feet (300 meters away); however, sources of light in the
surrounding region can decrease the NVG effectiveness to 164 feet (50 meters) or less,
depending on the amount of light and how close it is. Off‐installation lighting, such as
street lights or other elevated structures that are lit at night, produce a halo effect
around objects that further reduces visibility and resolution for air and ground personnel.
The amount of ambient light experienced on the ground is a function of:
Intensity of nearby light sources (up to 20 miles away);
Distance from the light sources;
Spectra of the light sources (blue light decays faster in the atmosphere);
Density of the cloud deck;
Height of the clouds; and
Relative humidity.
When measuring light pollution, proximity to a community has a significant effect on the
amount of light pollution that saturates the sky. For example, if proximity to lighting is
increased two‐fold, sky glow from the lighting will appear roughly six times brighter.
Figure 5‐17 provides a light pollution map of the JLUS Project Area. The map shows the
light pollution as measured in radiance units (W / cm2 * sr). The larger the number, the
greater the light pollution as shown by red shading on the map. Areas of the least light
pollution are shown in gray shading. The map was created using the “Light Pollution Map
Info” computer application. The application projects VIIRS data on top of land base data
layers such as roadways. Data collected from user light / darkness measurements can
also be projected using the map application. Areas colored red and yellow indicate
where there is greater light pollution, whereas gray and blue colors indicate lesser levels
of light pollution. As expected, greater amounts of light pollution are associated with
cities and other developed areas. The map is a useful reference tool in support of the
discussion presented in the compatibility assessments where light pollution is referenced.
Light pollution directly from fixtures or from light reflected off the ground or other
surfaces can interfere with military nighttime training activities. The impacts of outdoor
lighting in the region around an installation are determined by two primary factors–the
amount of developed land (density) and the distance of the developed land from the
installation.
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Compatibility Assessment