142
at the national level. These standards include principles, definitions of important tenninology, and the
National Vegetation Classification System (FGDC,
1997b). The NVCS is a hierarchical classification
system based on existing vegetation. The United
Nations Educational, Scientific, and Cultural Organization (UNESCO) originally developed this
system in the early 1970s, and The Nature Conservancy recently modified it for conservation planning. Several federal agencies are employing the
NVCS for resource inventory, management, monitoring, and conservation. Some recent vegetation
mapping activities and universal resource locators
(URLs) to project Web sites follow.
1. The USGS· Gap Analysis Program is mapping
vegetation at the state level using Landsat TM
imagery and the NVCS. (URL: http://www.
calrnit. unl.edul gapmap/)
2. The U.S. Fish and Wildlife Service is testing the
NVCS in a pilot project and hopes to classify
the entire National Wildlife Refuge System.
(URL: http://www.fws.gov/data/projcht2.html)
3. The National Park Service Vegetation Mapping
Program, based on the NVCS, is currently underway in all national parks. (URL: http://biology.usgs.gov /npsveg/nvcs.html)
4. The Forest Service used the NVCS for the ecological assessment of the Pacific Northwest Region Columbia River Basin. (URL: http://www.
icbemp.govl)
10.3.3 Change Detection
Change detection, the process of monitoring
changes in land coVer over time, is a very important use of remotely sensed data. Mapping changes
in land cover has many applications: updating vegetation layers; furnishing a historical context for
land management planning; evaluating changes in
patch characteristics relative to wildlife, water,
recreation, and timber resource management; and
understanding potential causes of change. Archives
of remotely sensed data exist as far back as the
1930s for aerial photography and to the early 1970s
for satellite imagery. For a general overview of
change detection, refer to Jensen (1996). A variety
of change detection techniques and applications exists and can be found in the literature. Collins and
Woodcock (1997) assess several change detection
techniques for mapping forest mortality in the Lake
Tahoe Basin area. Lyon et al. (1998) compared vegetation indices from Landsat MSS data for their
value for vegetation and land cover change detecRemote Sensing Applied to Ecosystem Management
tion over three time periods in Chiapas, Mexico.
Muchoney and Haack (1994) used an automated
approach to change detection to monitor forest defoliation in Virginia. Michener and Houhou1is
(1997) also used an automated change detection
process to monitor vegetation changes associated
with flooding caused by Tropical Storm Albert in
July 1994 in southwest Georgia. And Viedma et al.
(1997) used satellite imagery to assess regrowth
pattern of different species following a fire, to analyze the speed of recovery, and to estimate the
rates of regrowth in Alicante, Spain.
10.3.4 Access to Remotely Sensed Data
Remotely sensed data are available from numerous
sources. Listed next are the most commonly used
repositories for aerial photography and satellite imagery.
Consolidated Farm Service Agency Aerial
Photography Field Office
2222 West 2300 South, P.O. Box 30010
Salt Lake City, UT 84130-0010
(801) 975-3500
(URL: www.apfo.usda.gov)
Data available: Photography acquired by federal agencies that is less than 40 years old
National Archives and Records Administration
700 Pennsylvania Avenue, N.W.
Washington, DC 20408
(800) 234-8861
(URL: www.nara.gov)
Data available: Photography acquired by federal agencies that is more than 40 years old
EROS Data Center
47914 252nd Street
Sioux Falls, SD 57198-0001
(800) 252-4547 or (605) 594-6151
(URL: http://edcwww.cr.usgs.gov)
Data available: Satellite imagery and photography acquired by federal agencies that is less
than 40 years old
Space Imaging / EOSAT
12076 Grant Street
Thornton, CO 80241
(800) 425-2997
(URL: www.spaceimaging.com)
Data available: Satellite and radar data and
products
SPOT Image Corporation
1897 Preston White Drive
at the national level. These standards include principles, definitions of important tenninology, and the
National Vegetation Classification System (FGDC,
1997b). The NVCS is a hierarchical classification
system based on existing vegetation. The United
Nations Educational, Scientific, and Cultural Organization (UNESCO) originally developed this
system in the early 1970s, and The Nature Conservancy recently modified it for conservation planning. Several federal agencies are employing the
NVCS for resource inventory, management, monitoring, and conservation. Some recent vegetation
mapping activities and universal resource locators
(URLs) to project Web sites follow.
1. The USGS· Gap Analysis Program is mapping
vegetation at the state level using Landsat TM
imagery and the NVCS. (URL: http://www.
calrnit. unl.edul gapmap/)
2. The U.S. Fish and Wildlife Service is testing the
NVCS in a pilot project and hopes to classify
the entire National Wildlife Refuge System.
(URL: http://www.fws.gov/data/projcht2.html)
3. The National Park Service Vegetation Mapping
Program, based on the NVCS, is currently underway in all national parks. (URL: http://biology.usgs.gov /npsveg/nvcs.html)
4. The Forest Service used the NVCS for the ecological assessment of the Pacific Northwest Region Columbia River Basin. (URL: http://www.
icbemp.govl)
10.3.3 Change Detection
Change detection, the process of monitoring
changes in land coVer over time, is a very important use of remotely sensed data. Mapping changes
in land cover has many applications: updating vegetation layers; furnishing a historical context for
land management planning; evaluating changes in
patch characteristics relative to wildlife, water,
recreation, and timber resource management; and
understanding potential causes of change. Archives
of remotely sensed data exist as far back as the
1930s for aerial photography and to the early 1970s
for satellite imagery. For a general overview of
change detection, refer to Jensen (1996). A variety
of change detection techniques and applications exists and can be found in the literature. Collins and
Woodcock (1997) assess several change detection
techniques for mapping forest mortality in the Lake
Tahoe Basin area. Lyon et al. (1998) compared vegetation indices from Landsat MSS data for their
value for vegetation and land cover change detecRemote Sensing Applied to Ecosystem Management
tion over three time periods in Chiapas, Mexico.
Muchoney and Haack (1994) used an automated
approach to change detection to monitor forest defoliation in Virginia. Michener and Houhou1is
(1997) also used an automated change detection
process to monitor vegetation changes associated
with flooding caused by Tropical Storm Albert in
July 1994 in southwest Georgia. And Viedma et al.
(1997) used satellite imagery to assess regrowth
pattern of different species following a fire, to analyze the speed of recovery, and to estimate the
rates of regrowth in Alicante, Spain.
10.3.4 Access to Remotely Sensed Data
Remotely sensed data are available from numerous
sources. Listed next are the most commonly used
repositories for aerial photography and satellite imagery.
Consolidated Farm Service Agency Aerial
Photography Field Office
2222 West 2300 South, P.O. Box 30010
Salt Lake City, UT 84130-0010
(801) 975-3500
(URL: www.apfo.usda.gov)
Data available: Photography acquired by federal agencies that is less than 40 years old
National Archives and Records Administration
700 Pennsylvania Avenue, N.W.
Washington, DC 20408
(800) 234-8861
(URL: www.nara.gov)
Data available: Photography acquired by federal agencies that is more than 40 years old
EROS Data Center
47914 252nd Street
Sioux Falls, SD 57198-0001
(800) 252-4547 or (605) 594-6151
(URL: http://edcwww.cr.usgs.gov)
Data available: Satellite imagery and photography acquired by federal agencies that is less
than 40 years old
Space Imaging / EOSAT
12076 Grant Street
Thornton, CO 80241
(800) 425-2997
(URL: www.spaceimaging.com)
Data available: Satellite and radar data and
products
SPOT Image Corporation
1897 Preston White Drive