Library of Congress Geography and Maps: An

Illustrated Guide
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Aerial Photographs and Remote Sensing Images

Landsat revealed whole new worlds hidden within the folds of a familiar world we thought we knew so well.

Mapping the Next Millennium, 1992

The urge to view the earth from above has deep historic roots. With the advent of human ight and the invention of photography, aerial images of the Earth's surface became an important tool in scientific, technical, and cartographic disciplines.

Aerial photographs, or printed versions known as photomaps, are found in many portions of the collections such as the Edgar Tobin Aerial Surveys Collection and the Nirenstein National Reality Company Collection. Many World War II era maps filed in the general collections are in the form of photomaps because they could be produced rapidly by tactical mapping units in the field to support military actions on the ground and for the identification of bombing targets.

Thumbnail image of photomosaic of

Manhattan Island, New York Detail of a photomosaic of Manhattan Island, New York, showing the lower portion of the island. Constructed from 100 aerial photographs taken by Fairchild Aerial Camera Corporation at an altitude of 1,000 feet on August 4, 1921, the photomosaic measures over eight feet in length. (Vault Map Collection)

The development of color photography and other specialized films expanded the range of applications to which aerial photography could be applied. In particular, the use of infrared film, which had a profound impact on the mapping of forests and crops, is well represented in the division's Remote Sensing Imagery and Aerial Photography Browse File. Aerial photography is such an important scientific tool that astronauts in virtually all of America's space programs have devoted time to taking hand-held photographs of the Earth. The division holds some 85,000 of these photographs on 16mm color film taken during Apollo, Gemini, Skylab, and Space Shuttle missions.

Just as the coincidental development of human ight and photography provided an impetus for change, the concurrent development of earth-orbiting satellites and computers marks another great milestone in cartographic history. Satellites provided a relatively inexpensive platform from which cameras could survey the earth on a regular basis. Computers and related technologies provided the foundation for a digital form of observation that eliminated the need for photographic film.

Thumbnail image of 1980 coverage of

Carver County, Minnesota Access to conventional black and white aerial photography is provided by microfiche copies of photomosaic indexes, such as this 1980 coverage of Carver County, Minnesota by the Agricultural Stabilization and Conservation Service. (Remote Sensing and Aerial Photography Browse File)

This revolutionary discipline was developed by the United States with the launching of the first Earth Resource Technology Satellite (later renamed Landsat) by nasa in 1972. Through the support of the U.S. Geological Survey and the National Oceanic and Atmospheric Administration in 1985, the division acquired approximately 650,000 16mm black-and-white photographic images of most countries generated from Landsat sensing devices at an altitude of some 570 miles. nasa also has deposited 630 eight- by ten-inch color photo images generated from Landsat satellites 1, 2, and 3 launched between 1972 and 1978. The photographs were selected by nasa scientists to illustrate significant geologic and topographic features and to demonstrate the value of Landsat imagery for scientific inquiry. Earth Observation Satellite Corporation, a private firm that currently manages the Landsat program for the federal government, recently donated a collection of 120 large format printed images generated from Landsat 4 and 5, representing many different areas of the world. A number of Landsat images produced by foreign organizations have also been acquired. The World Bank donated a set of nineteen satellite image maps of Nepal prepared by the Nepal National Remote Sensing Center in 1986.

Thumbnail image of The confluence of the Rio Negro and the Amazon River in Brazil is shown on this Landsat image. Unlike a conventional photograph, this is a computer-generated image derived from reflected energy collected by a mapping satellite orbiting the earth at a distance of 438 miles. A false color image, the deep reds indicate the dense vegetation of the Amazon rain forests, while the lighter reds following the linear patterns of the road network reflect areas of deforestation. The heavily sedimented Rio Negro is shown in black while the Amazon appears in blue. (Earth Observation Satellite Company Collection)

Remote sensing will greatly alter the nature of cartography. Consequently, the Geography and Map Division will be collecting this new format of geographic information to complement the several centuries worth of traditional cartographic images of the earth that it holds. This new technology is highly dependent on powerful computers, and efforts are under way to provide the hardware and software necessary to use remotely sensed images of the earth. To date, the division has relied on collecting printed products derived from satellite imagery. Soon, however, government agencies and private firms will be releasing the digital forms of these images, and the division will begin collecting, cataloging, and servicing the actual data.

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