|Color United States Shaded Relief – 200
What this map layer shows:
The shape of the land surface of the United States, in color and at
a resolution of 200 meters.
Also available is Color North America Shaded Relief – 1
The National Elevation Dataset (NED)
is a raster product assembled by the U.S.
Geological Survey (USGS), designed to provide national elevation data
in a seamless form with a consistent datum, elevation unit, and projection.
Each grid cell in the national elevation model has a value that represents
the average height above sea level within that cell. Data corrections made
in the NED assembly process minimize artifacts, permit edge matching, and
fill sliver areas of missing data. Elevation data are an essential part
of many earth science applications. They are used for such diverse purposes
as providing shaded-relief backgrounds, establishing stratification in
land cover classification, doing geometric and radiometric correction of
remotely sensed data, and determining landform characteristics such as
slope and aspect. The Color United States Shaded Relief – 200 Meter
Resolution map layer was derived from NED data and was produced by the
National Atlas of the United States® with data provided
by the USGS Center for
Earth Resources Observation and Science (EROS).
The map layer was produced by combining two images. The first
was a color elevation image, created by grouping the elevation values
into ranges and then assigning colors to the different elevation ranges.
The second was a grayscale shaded relief image, in which a three-dimensional
appearance was achieved by determining a gray tone at each point, calculated
from the steepness of the slope combined with illumination as if there
were a light source in the northwest.
The Color United States Shaded Relief – 200 Meter Resolution map
layer is four shaded-relief images showing the terrain of the conterminous
United States, Alaska, Hawaii, and Puerto Rico and the U.S. Virgin Islands.
A separate image was created for each of the four areas of the United
States because, at 200 meter resolution, file size for an elevation mosaic
of all of the United States would exceed the processing capacity of some
commonly-used GIS and image processing software packages. The image is
intended for visual purposes only; the original NED data must be used
for conducting analysis and determining elevation values.
The Color United States Shaded Relief – 200 Meter Resolution
map layer is available in both a Lambert Azimuthal Equal-Area projection
and an Albers Conical Equal-Area projection. Only the Lambert files
can be viewed with the National Atlas Map Maker.