G-11
Glossary
Union the operation wherein the chosen features are
all that meet the first criteria as well as all that meet
the second criteria in the query.
union (overlay) a type of GIS overlay that combines
all features from both layers.
Universal Transverse Mercator (UTM) the grid
system of locating coordinates across the globe.
US Topo a digital topographic map series created by
the USGS to allow multiple layers of data to be used
on a map in GeoPDF file format.
user segment one of the three segments of GPS,
consisting of the GPS receivers on the ground that pick
up the signals from the satellites.
UTM zone one of the 60 divisions of the world set up
by the UTM system, with each zone being 6 degrees of
longitude wide.
UV (ultraviolet) the portion of the electromagnetic
spectrum with wavelengths between 0.01 and 0.4
micrometers.
vector data model a conceptualization of
representing spatial data with a series of vector objects
(points, line, and polygons).
vector objects points, lines, and polygons that are
used to model real-world phenomena using the vector
data model.
vehicle navigation system a device used to plot the
user’s position on a map, using GPS technology to
obtain the location.
vertical datum a baseline used as a starting point in
measuring elevation values (either above or below this
value).
vertical exaggeration a process whereby the z-values
are artificially enhanced for terrain visualization
purposes.
vertical photo an aerial photo in which the camera is
looking down at a landscape.
VGI Volunteered Geographic Information, a term
used to describe user-generated geospatial content
and data.
viewshed a data layer that determines what an
observer can see and cannot see from a particular
location due to terrain.
virtual globe a software program that provides an
interactive three-dimensional map of Earth.
Visible Earth a Website operated by NASA to
distribute EOS images and animations of EOS
satellites or datasets.
visible light the portion of the electromagnetic
spectrum with wavelengths between 0.4 and 0.7
micrometers.
visual image interpretation the process of
discerning information to identify objects in an aerial
(or other remotely sensed) image.
WAAS the Wide Area Augmentation System—a
satellite based augmentation system that covers
the United States and other portions of North
America.
wavelength the distance between the crests of two
waves.
WGS84 the World Geodetic System of 1984 datum
(used with the Global Positioning System).
wiki a database available so that anyone can edit it.
WorldView-1 a satellite launched in 2007 by the
DigitalGlobe company, whose panchromatic sensor
has 0.5-meter spatial resolution.
WorldView-2 a satellite launched in 2009 by
the DigitalGlobe company, featuring an 8-band
multispectral sensor with 1.84-meter resolution
and a panchromatic sensor of 0.46-meter resolution.
Worldwide Reference System the global system of
Paths and Rows that is used to identify what area on
Earth’s surface is present in which Landsat scene.
XOR the Boolean operator that corresponds with an
Exclusive Or operation.
Y code an encrypted version of the P code.
z-value the elevation assigned to an x/y coordinate.
Glossary
Union the operation wherein the chosen features are
all that meet the first criteria as well as all that meet
the second criteria in the query.
union (overlay) a type of GIS overlay that combines
all features from both layers.
Universal Transverse Mercator (UTM) the grid
system of locating coordinates across the globe.
US Topo a digital topographic map series created by
the USGS to allow multiple layers of data to be used
on a map in GeoPDF file format.
user segment one of the three segments of GPS,
consisting of the GPS receivers on the ground that pick
up the signals from the satellites.
UTM zone one of the 60 divisions of the world set up
by the UTM system, with each zone being 6 degrees of
longitude wide.
UV (ultraviolet) the portion of the electromagnetic
spectrum with wavelengths between 0.01 and 0.4
micrometers.
vector data model a conceptualization of
representing spatial data with a series of vector objects
(points, line, and polygons).
vector objects points, lines, and polygons that are
used to model real-world phenomena using the vector
data model.
vehicle navigation system a device used to plot the
user’s position on a map, using GPS technology to
obtain the location.
vertical datum a baseline used as a starting point in
measuring elevation values (either above or below this
value).
vertical exaggeration a process whereby the z-values
are artificially enhanced for terrain visualization
purposes.
vertical photo an aerial photo in which the camera is
looking down at a landscape.
VGI Volunteered Geographic Information, a term
used to describe user-generated geospatial content
and data.
viewshed a data layer that determines what an
observer can see and cannot see from a particular
location due to terrain.
virtual globe a software program that provides an
interactive three-dimensional map of Earth.
Visible Earth a Website operated by NASA to
distribute EOS images and animations of EOS
satellites or datasets.
visible light the portion of the electromagnetic
spectrum with wavelengths between 0.4 and 0.7
micrometers.
visual image interpretation the process of
discerning information to identify objects in an aerial
(or other remotely sensed) image.
WAAS the Wide Area Augmentation System—a
satellite based augmentation system that covers
the United States and other portions of North
America.
wavelength the distance between the crests of two
waves.
WGS84 the World Geodetic System of 1984 datum
(used with the Global Positioning System).
wiki a database available so that anyone can edit it.
WorldView-1 a satellite launched in 2007 by the
DigitalGlobe company, whose panchromatic sensor
has 0.5-meter spatial resolution.
WorldView-2 a satellite launched in 2009 by
the DigitalGlobe company, featuring an 8-band
multispectral sensor with 1.84-meter resolution
and a panchromatic sensor of 0.46-meter resolution.
Worldwide Reference System the global system of
Paths and Rows that is used to identify what area on
Earth’s surface is present in which Landsat scene.
XOR the Boolean operator that corresponds with an
Exclusive Or operation.
Y code an encrypted version of the P code.
z-value the elevation assigned to an x/y coordinate.