NOAA CoastWatch produces near real-time true color satellite images
for U.S. coastal regions
from the Visible Infrared Imaging Radiometer Suite (VIIRS)
on-board the polar-orbiting Suomi-NPP satellite.
True color satellite images are like a camera photo.
The instrument's visible measurements at the red, green, and blue
wavelengths are combined to create a color-realistic image, just
like a digital photograph.
Land and water features can be seen in these images. Because cloud
coverage is very obvious, these images can be used to quickly determine
if a particular day's image is useful for observing a land or water feature.
NOAA/NESDIS processes the VIIRS Sensor Data Record (SDR) calibrated
radiances for all wavelengths, and CoastWatch then generates data files
of the red, green and blue surface reflectance measurements for
generating true color images.
Currently, CoastWatch true color data and image
files are available for the VIIRS instrument's 750 m
spatial resolution wavelength bands. The surface reflectances are
corrected for atmospheric effects, such as a Rayleigh correction.
In the future, CoastWatch anticipates
offering true color data and images at the much higher spatial resolution
of 375 m for U.S. coastal regions.
NOAA CoastWatch East Coast Node began featuring true color images made
with surface reflectance on November 9, 2018. Before that, true color
images were made with top-of-atmosphere radiance, without atmospheric
corrections. Below is a comparison of the two approaches. True color
made from surface reflectance offers clearer, brighter images.