An investigation into the comparative utility of color infrared aerial photography and LANDSAT data for detailed surface cover type mapping within Crater Lake National Park, Oregon
The identification and mapping of surface cover types
within Crater Lake National Park, Oregon, has been effectively
completed through the utilization of LANDSAT digital
data and NASA U-2 color infrared aerial photography. Classification
of LANDSAT data for surface cover type identification
and mapping was accomplished through use of the
Interactive Digital Image Manipulation System (IDIMS) which
provided enormous classification flexibility due to the
interactive capability of IDIMS and its color video display.
LANDSAT data extraction techniques employed in this
research include the generation of grayscales; density
slice; spectral reflectance plots versus pixel frequency
and LANDSAT bands for low sun angle and medium to high sun
angle LANDSAT digital tape dates; spectral relationship
plots; and control clustering of training set selection.
The use of these techniques produced training statistics
which show "good" class discrimination for study area
classification. A covariance matrix, weighted divergence,
and distance between clusters were generated for each of
the 59 training classes to determine if any of the classes
were statistically related and should be combined.
Slope angle, slope aspect, and surface cover type
variation, and to a lesser degree, crown size and crown
density are the main environmental factors which account
for spectral reflectance variation of surface cover types
within Crater Lake National Park. Through an understanding
of the influence of environmental factors in the reflectance
value of surface cover types, one can evaluate
the quality of training statistics and the location of
training areas in order to reduce mis-classification or
non-classification possibilities. A regression analysis,
analysis of variance, T-values, F-values, and beta values
were used to determine the relative degree that certain
environmental factors influence the spectral reflectance
of surface cover types producing a change in the mean reflectance
of surface cover types per LANDSAT band.
LANDSAT classification accuracy levels for 12 major
surface cover types within Crater Lake National Park range
from 84 to 98 percent. Accuracy levels are inversely related
to the level of detail sought and obtained.
LANDSAT's primary advantages over NASA U-2 color
infrared aerial photography for surface cover type identification
and mapping include: repetitive coverage; computer
compatibility of data without photographic digitizing;
multi-spectral scanner capability; and the further extension
of wavelengths into the near infrared. The NASA U-2
aerial photography's primary advantages (over LANDSAT) for
surface cover type identification and mapping include:
increased scale; greater resolution; and stereoscopic
viewing. Stereoscopic viewing was accomplished through
use of an Old Delft Scanning stereoscope which provided
1.5 to 4.5 magnification.
"Ground truth" is the link between LANDSAT data,
aerial photography, and actual ground conditions. "Ground
truth" should measure and/or observe surface cover types
and parameters which are capable of influencing the
spectral reflectance as detected by LANDSAT. Geologic
activity, soil conditions, vegetation, and climate have in
the past and do in the present influence the spectral reflectance
of surface cover types within Crater Lake
National Park, Oregon