This color shaded relief image shows the extent of digital elevation
data for Africa recently released by the Shuttle Radar Topography Mission
(SRTM). This release includes data for all of the continent, plus the
island of Madagascar and the Arabian Peninsula. SRTM flew on board the
Space Shuttle Endeavour in February 2000 and used an interferometric
radar system to map the topography of Earth's landmass between latitudes
56 degrees south and 60 degrees north.
The data were processed into geographic "tiles," each of which
represents one by one degree of latitude and longitude. A degree of
latitude measures 111 kilometers (69 miles) north-south, and a degree
of longitude measures 111 kilometers or less east-west, decreasing away
from the equator. The data are being released to the public on a
continent-by-continent basis. This Africa segment includes 3256 tiles,
almost a quarter of the total data set. Previous releases covered North
America, South America and Eurasia. Forthcoming releases will include
Australia plus an "Islands" release for those islands not included in
the continental releases. Together these data releases constitute the
world's first high-resolution, near-global elevation model. The
resolution of the publicly released data is three arcseconds (1/1,200
of a degree of latitude and longitude), which is about 90 meters (295
feet).
Coverage in the current data release extends from 35 degrees north
latitude at the southern edge of the Mediterranean to the very tip of
South Africa, encompassing a great diversity of landforms. The northern
part of the continent consists of a system of basins and plateaus, with
several volcanic uplands whose uplift has been matched by subsidence in
the large surrounding basins. Many of these basins have been infilled
with sand and gravel, creating the vast Saharan lands. The Atlas
Mountains in the northwest were created by convergence of the African
and Eurasian tectonic plates.
The geography of the central latitudes of Africa is dominated by the
Great Rift Valley, extending from Lake Nyasa to the Red Sea, and
splitting into two arms to enclose an interior plateau and the nearly
circular Lake Victoria, visible in the right center of the image. To
the west lies the Congo Basin, a vast, shallow depression which rises
to form an almost circular rim of highlands.
Most of the southern part of the continent rests on a concave plateau
comprising the Kalahari basin and a mountainous fringe, skirted by a
coastal plain which widens out in Mozambique in the southeast.
Many of these regions were previously very poorly mapped due to
persistent cloud cover or the inaccessibility of the terrain. Digital
elevation data, such as provided by SRTM, are particularly in high demand
by scientists studying earthquakes, volcanism, and erosion patterns for
use in mapping and modeling hazards to human habitation. But the shape of
Earth's surface affects nearly every natural process and human endeavor
that occurs there, so elevation data are used in a wide range of
applications.
In this index map color-coding is directly related to topographic
height, with brown and yellow at the lower elevations, rising through
green, to white at the highest elevations. Blue areas on the map
represent water within the mapped tiles, each of which includes
shorelines or islands.
Elevation data used in this image were acquired by the Shuttle Radar
Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched
on February 11, 2000. SRTM used the same radar instrument that comprised
the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar
(SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994.
SRTM was designed to collect three-dimensional measurements of the
Earth's surface. To collect the 3-D data, engineers added a 60-meter-long
(200-foot) mast, installed additional C-band and X-band antennas, and
improved tracking and navigation devices. The mission is a cooperative
project between the National Aeronautics and Space Administration (NASA),
the National Geospatial-Intelligence Agency (NGA) of the U.S. Department
of Defense (DoD), and the German and Italian space agencies. It is managed
by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth
Science Enterprise, Washington, DC.
Orientation: North toward the top, Mercator projection
Image Data: Colored SRTM elevation model
Date Acquired: February 2000