Remote sensing is the science of deriving information about an object or phenomenon at or near the surface of the earth through the analysis of data acquired by a camera or sensor system located in an aircraft or orbiting satellite. One of the ways in which remote sensing imagery has commonly been used is to derive information regarding surface, or land cover characteristics.
At the site level and for small regions, land cover data has typically been obtained from the interpretation of aerial photography, and more recently from digital orthophotography. At the statewide level, land cover information is usually produced from the analysis of satellite imagery and the resulting inventory can provide accurate, regional level information for natural resource applications.
Since July 1972, the US Landsat satellite system has been providing continuous coverage of multispectral imagery for Illinois, providing the best cost-for-benefit of any satellite system when assessing large geographic areas.
All of the primary source imagery used for the Land Cover of Illinois 1999-2000 initiative has been derived from the Landsat 5 and 7 satellites, and detailed information about these systems is available online at http://edc.usgs.gov/glis/hyper/guide/landsat_tm.html and http://landsat7.usgs.gov, or by contacting the U.S. Geological Survey EROS Data Center at:
U.S. Geological Survey
EROS Data Center
47914 252nd Street
Sioux Falls, SD 57198-0001
Tel: 800.252.4547 or 605.594.6151
Web site: http://edc.usgs.gov/
Some Basic Concepts
- Land is the raw material of Illinois. Current and detailed information regarding this fundamental natural resource is essential for making wise decisions affecting the land and ensuring good stewardship. The terms land use and land cover are commonly used together or sometimes interchangeably to describe the same type of information, and therefore some clarification is advisable.
- Land use refers to human activities occurring on the land and emphasizes the principal role of land in describing a region's economic activities. Since the concept describes human activity, land use is not directly observable from remote sensing imagery alone. The presence of forested land in an aerial photograph or satellite image does not always convey the possible multiple uses of that land, which may include recreation, wildlife refuge, timber production, or residential development.
- Land cover refers to the vegetative and manmade features covering the land surface, all of which can be directly observed using remote sensing imagery. Whereas land use is abstract, land cover is tangible and can be determined by direct inspection of the earth surface using remote sensing imagery. Expressed another way, land cover is the visible evidence of land use (Campbell 1987). Furthermore, in areas where natural vegetation predominates, land cover information can be used as a surrogate for ecosystems in natural resource assessments because vegetation effectively integrates many physical and biological factors within a geographic area (Scott 1993).