The Shuttle Radar Topography Mission (SRTM) has produced the first
high-resolution, near-global elevation dataset of Earth. In recognition
of this achievement, and as an illustration of the data, the United States
Library of Congress now displays a "solid terrain model" of Los Angeles
and adjacent mountainous terrain. The model was created by carving a
high-density foam block using computer-guided drills that referenced the
SRTM dataset. The block was then covered with a Landsat satellite image
using computer-guided paint guns that referenced both the Landsat image
and the SRTM dataset. The view shown here mimics the actual model on
display at the Library of Congress and was generated from the same
satellite image and elevation data sets.
The model shows the Pacific Ocean and Santa Monica Mountains along the
Malibu Coast (lower left), San Fernando Valley (left center), downtown
Los Angeles (bottom center), San Gabriel and Pomona Valleys (lower right),
San Gabriel Mountains (right center to far right), and part of the Mojave
Desert (upper right). Colors are enhanced true color with added
topographic shading, and elevation differences are exaggerated 1.5
times. The view is toward the north-northwest.
The Los Angeles region was chosen for the Library of Congress model
because it illustrates so many ways that topography affects the daily
lives of people. The region consists of a coastal plain, inland valleys,
mountains up to 3068 meters (10,064 feet), and a desert interior.
Topography blocks the landward influence of marine airmasses here such
that summer temperatures often differ by 40 degrees Fahrenheit (22 C)
across this region at a given moment even at similar elevations.
Temperatures also typically cool with rising elevation, and winter storms
drop most of their moisture in the mountains, leaving little rainfall for
areas further inland, thus creating the deserts.
Topography also controls the land use pattern. The mountains are mostly
very rugged, which greatly limits urban expansion. Similarly, major
transportation routes are limited to a few mountain passes. Water supply
to the city and drainage away from it both follow paths largely dictated
by topography. Radio, television, and cell phone transmission towers are
all sited with topography in mind to maximize coverage.
Its climate and scenic mountain surroundings have been a major part of
the appeal of the Los Angeles region as it has grown into one of the
world's largest cities over the past 150 years. But the topography that
has created this environment also results from and leads to significant
natural hazards. The tall mountains result from tectonic compression and
uplift of Earth's crust along a kink in the San Andreas fault. (The fault
is seen here as a straight boundary between the Mojave Desert and the San
Gabriel Mountains.) Major earthquakes occur on the San Andreas fault every
few centuries. Damaging earthquakes also occur on other faults across the
region several times in a typical human lifespan. Most of these faults
were first recognized by their impact upon the topographic pattern.
Meanwhile, wildfires are common in the chaparral covered hills and
mountains, and topography affects the fire's path (burning more readily
upslope) as well as our ability to fight it. After a fire, rainfall from
winter storms often strips exposed soil, accumulates it as mudflows in
rugged canyons, and dumps it into the adjacent valleys which are now
heavily urbanized. Topography is indeed important in the lives of the
people of Los Angeles.
Landsat has been providing visible and infrared views of the Earth since
1972. SRTM elevation data substantially help in analyzing Landsat images
by revealing the third dimension of Earth's surface, topographic height.
The Landsat archive is managed by the U.S. Geological Survey's Eros Data
Center (USGS EDC).
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.
Size: Block length 120 kilometers (74 miles), block width 60 kilometers (37 miles)
Location: 34.2 degrees North latitude, 118.3 degrees West longitude
Orientation: View North-Northwest, 1.5 times vertical exaggeration
Image Data: Landsat bands 3, 2, 1 as red, green, blue, respectively, plus elevation shading.
Date Acquired: February 2000 (SRTM), May 4, 2001 (Landsat)