Ultraviolet absorbing filter: A haze-cutting filter used mainly in
photography with colour films to avoid excessive bluishness and loss of
contrast in the pictures.
Ultraviolet radiation: Electromagnetic radiation of shorter wavelength
than visible radiation but longer than X-rays; roughly, radiation in the
wavelength interval 10 - 4000 Å.
UN: United Nations.
Uncontrolled mosaic: A mosaic of image or photographic data which
is made without correcting for type of geometric distortions.
Universal Transverse Mercator (UTM): International series of Transverse
Mercator projections in which the central meridians are aligned with meridians
of longitude. The series divides the globe into 60 zones of 6 degrees longitude.
Unsupervised classification: A procedure for classifying an image
without any pre-defined classes.
USDA: United States Department of Agriculture.
User-friendly: Jargon term often associated with equipment or a technique
that is easy to use.
USGS: United States Geological Survey.
UTM: Universal Transverse Mercator projection.
UV: UltraViolet.