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Satellite View of the United States,
with Shaded Relief |
What this map layer shows:
Simulated-natural-color
images of the United States, with relief enhanced by shading. |
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Background Information |
Sample Map
The Landsat Project is
a joint effort of the U.S.
Geological Survey (USGS) and the National
Aeronautics and Space Administration (NASA). Since 1972, NASA has developed
and launched seven Landsat satellites. The USGS is responsible for ground
data reception, processing, product generation, and archiving. The primary
purpose of Landsat is to provide regular, repeated coverage to support
the analysis of changes on the Earth's land surface. Landsat images provide
a steady flow of data for use in a wide range of applications such as global
change research, agriculture, forestry, geology, mapping, water quality,
and oceanography.
Landsats 5 and 7, the two remaining operational Landsat satellites,
fly at an altitude of approximately 438 miles (705 km) and collect
data in 7 spectral bands over a 115-mile (185-km) swath. The sensors
detect reflected or emitted energy from the Earth in the visible
and near-infrared wavelengths. The satellite orbits are Sun-synchronous,
which means that the satellites move north to south on the sunlit side
of the Earth and cross the equator at the same time each day. Each
point on the Earth's land surface is imaged by Landsat once every 16
days.
The National Elevation
Dataset (NED) is a raster product assembled by the USGS. The NED
is designed to provide national elevation data in a seamless form with
a consistent datum, elevation unit, and projection. Data corrections
are made in the NED assembly process to minimize artifacts, perform edge
matching, and fill sliver areas of missing data. The NED has a resolution
of one arc-second (approximately 30 meters) for the conterminous United
States, Hawaii, Puerto Rico and the island territories and a resolution
of two arc-seconds for Alaska.
The Satellite View with Shaded Relief map layers were produced by combining
Landsat Thematic Mapper (TM) imagery, from bands 2, 4, and 7 of the
Landsat 4 (operational from 1982-2001) and Landsat 5 satellites, with
NED data. The result is 200-meter-resolution simulated-natural-color
images with relief enhanced by shading. Vegetation is generally green,
with forests in darker green and grasslands, shrublands, or vegetative
tundra in lighter green. Areas of high reflectance, including urban
areas, rock, and dry bare soil, are shown in shades of pink. Very bright
areas, such as snow and ice, are colored blue. The color of water bodies
is influenced by natural and man-made factors such as differences in
depth, salinity, pollution, and sediment load, which affect the reflectance
of the area. There is one image for the conterminous United States,
one for Alaska, and one for Hawaii. The images were developed by the
National Atlas of the United States® with data provided
by the USGS Center
for Earth Resources Observation and Science (EROS). EROS archives,
processes, and distributes remotely sensed data, including satellite
images and aerial photographs, and works with agencies and organizations
around the world to support studies using remotely sensed data.
For further information on the source data, see the Landsat
fact sheet and the NED
fact sheet. Mosaics of TM images, adjusted to correct for positional
accuracy and relief displacement, and covering an area of 5 degrees
latitude by 6 degrees longitude, are available through the Landsat
Orthorectified TM Mosaic page.
The National Atlas also includes 200-meter-resolution simulated-natural-color
images of the United States which do not include shaded relief. |
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