Mapping Technology

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Mapping Technology

█ WILLIAM C. HANEBERG

Mapping technology is a broad term that describes the equipment and techniques used to prepare, analyze, and distribute maps of all kinds. This can include satellites used to obtain high resolution and multispectral data; software to enhance or classify digital images; global positioning system (GPS) satellites; and geographic information systems (GIS).

Intelligence-related mapping within the United States is largely the responsibility of the National Imagery and Mapping Agency. It was formed in 1996 by consolidating the capabilities of several federal agencies involved with the acquisition and analysis of imagery and other forms of geospatial intelligence. The U.S. Geological Survey, a civilian agency within the Department of the Interior, produces detailed topographic and geologic maps of areas within the United States.

One of the primary uses of mapping technology is to gather data from which maps can be made. Classified images from intelligence satellites and sub-meter resolution images from both government and commercial satellites can be used to obtain information about the civil and military infrastructure of foreign powers without having to set foot in dangerous or restricted areas. Technologies such as interferometric synthetic aperture radar (InSAR) can be used to create digital elevation models (DEMs) depicting the elevation of the Earth's surface and serve as the basis for detailed topographic maps. The Shuttle Radar Topography Mission, flown in February 2000, used specialized InSAR technology to map the elevation of Earth's land surface between 60 degrees north and 56 degrees south latitude. Elevations were measured every arc-second of latitude and longitude, which is equivalent to a spacing of about 30 m. Detailed topographic information such as that collected by the Shuttle Radar Topography Mission can be used to create topographic maps that are essential to military operations or to depict realistic landscapes in combat training simulators.

Multispectral imagery is created using sensors that respond to different bands within the visible and invisible portions of the electromagnetic spectrum. An image that appears to be a color photograph may actually be a color composite composed of, at minimum, red, blue, and green bands. Hyperspectral images are those in which the spectrum is divided into many narrow bands instead of several broad bands. Multispectral or hyperspectral image processing can be used to make inferences about soil or bedrock type, soil moisture, crop growth, chemical pollution, and other properties. Military or intelligence applications can include the determination of the ground conditions to be encountered by an invasion force or estimation of an enemy's crop production. Domestic applications include monitoring elements of a nation's infrastructure, for example unguarded energy transmission lines that are vital to national security and may present targets to terrorist networks.

The global positioning system (GPS) is a network of 24 satellites orbiting Earth at an altitude of 20,200 m (12.55 mi). Launched and maintained by the United States military, the satellites issue signals that can be decoded by GPS receivers to determine the location of the receiver and the time within several hundred nanoseconds. While it is principally a navigational system, GPS is also an important piece of mapping technology. Scientists, geographers, land surveyors, and others can use GPS to determine with great accuracy the locations of objects to be shown on maps. GPS receivers installed on moving vehicles, for example trucks carrying nuclear materials, allow them to be continuously tracked and maps of their locations updated in real time.

Geographic information system (GIS) software allows users to digitally store, retrieve, analyze, and display maps of all kinds. Maps created using different scales or projections can be adjusted and combined to form new composite maps that answer specific questions. For example, a GIS user can combine a computer model of air pollution dispersion with meteorological and troop location data to simulate the effects of possible chemical weapons attacks in different locations. GIS is likewise useful for homeland security projects such as constructing maps of critical infrastructure, developing emergency response plans, and evaluating the consequences of terrorist attacks.

█ FURTHER READING:

BOOKS:

Burrough, P. A., and R. A. McDonnell. Principles of Geographic Information Systems, 2nd ed. Oxford: University Press, 1998.

Wilford, G. N. The Mapmakers. New York: Knopf, 2000.

ELECTRONIC:

National Imagery and Mapping Agency. "NIMA Home." <http://www.nima.mil/>(December 9, 2002).

National Imagery and Mapping Agency. "Shuttle Radar Topography Mission Navigation Page." October 11,2002. <http://www.nima.mil/srtm/navigation.html> (December 9, 2002).

Dana, Peter H. "The Global Positioning System." May 1, 2000. <http://www.colorado.Edu/geography/gcraft/notes/gps/gps_f.html> (December 9, 2002).

Lawrence Livermore National Laboratory. "GIS Group Home Page." August 24, 2000. <http://gis.llnl.gov/indexm.html>(December 9, 2002).