Red River of the North Basin
National Water-Quality Assessment Program
Lorenz, D.L., 1994, Use of Remotely Sensed Data to Characterize Vegetation
in the Red River of the North Basin, Minnesota, North Dakota, and South Dakota in: Balthrop, B.H., and Baker, E.G., compilers, U.S. Geological Survey National Computer Technology Meeting, - Program and Abstracts, New Orleans, Louisiana, April 10-15, 1994, U.S. Geological Survey Open-File Report 94-52, p. 27.
Abstract
Remotely sensed data were processed by cluster analysis to evaluate vegetatives
cover in the Red River of the North Basin. This information provided a
general classification of vegetation that was used to interpret regional
water-quality data collected as a part of the National Water Quality
Assessment Program of the U.S. Geological Survey.
Vegetative index data, available from the EROS Data Center of the U.S.
Geological Survey, are biweekly composites of advanced very-high-resolution
radiometer data from the NOAA-11 satellite. The transmitted data are
corrected for reflectance, calibrated for receiver sensitivity, and registered
to a Lambert Azimuthal Equal-Area projection. The data in the near infrared
and visible bands are normalized to represent green vegetation and termed the
Normalized Difference Vegetation Index.
The Normalized Difference Vegetation Index data from twelve 2-week periods
(April 27 to October 11, 1990) were classified on the basis of the timing of
the greenness of the vegetation through a two-step cluster analysis. In the
first step, the data from each of the 259, 521 pixels were put into 128
disjoint clusters. In the second step, the data from the 128 clusters were
put into 13 hierarchical clusters. Visual inspection of the 13 clusters
produced 8 distinct groups (4 agricultural groups, 2 water groups, 1 forested
group, and 1 wetland group).
Based on the timing of vegetation greenness, three 2-week periods appeared to
be critical for discerning the groups. The 2-week periods were May 25-June 7,
June 8-21, and September 14-27, 1990. Classification based on these 3 periods
gave sharper, better defined groups than that based on all 12 periods.
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