The three-dimensional model of the northern metropolitan area of Los Angeles and the adjacent San Gabriel Mountains that is on display outside the Library's Geography and Map Division in the Madison Building illustrates the global terrain mapping capabilities now provided by earth-orbiting spacecraft.
The 48-by-56-inch model shows an area of 40.5 miles by 81 miles, for a total of 3,280.5 square miles, and vividly depicts the interaction of land, sea and air in the landscape pattern surrounding Los Angeles. Physical relief models such as this present a level of geographic understanding not found on flat computer-screen models or sheet-maps.
Southern California is earthquake country, and the largest fault, the San Andreas, is seen here as the linear boundary between the mountains and the adjacent dry and smooth desert terrain to the northwest. Although generally true, the model's colors have been enhanced by image processing and the inclusion of some green infrared reflectance to highlight healthy vegetation patterns.
The elevation data used to create the model were obtained from the Shuttle Radar Topography Mission (SRTM) that flew onboard the Space Shuttle Endeavor during an 11-day mission in February 2000. The SRTM is an international project headed by the Jet Propulsion Laboratory (JPL) at the California Institute of Technology in Pasadena for the National Aeronautics and Space Administration (NASA) and the National Imagery and Mapping Agency. The model was presented to the Library by NASA and the JPL.
To acquire topographic (elevation) data, the SRTM payload was outfitted with two radar antennas. A transmitting and receiving antenna was located in the shuttle's payload bay, and a second receiving antenna was located on the end of a 200-foot mast that extended from the payload bay once the Shuttle was in space. Differences in the radar signals reflected by the earth's surface and then received by the two antennas were used to calculate variations in elevation.
With its radars sweeping most of the earth's land surfaces, SRTM produced the world's first near-global high-resolution topographic database. The model was manufactured by Solid Terrain Modeling of Fillmore, Calif., which used the SRTM digital elevation data to control its cutting and printing machines. The elevation model was cut into high-density polyurethane foam. A color image covering the Los Angeles area, which was obtained from a Landsat-7 satellite on May 4, 2001, was then printed directly onto the model.