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ERDC/CRREL TR-02-11
rafters appear over bright interior concrete subflooring, and both are in or near
saturation. Note that pool-house rafters over the swimming pool, visible on the
neighboring house, are easily distinguishable due to the contrast of the dark blue
of the pool with the white rafters. The status of individual rafters may not always
be determined during new construction with 1-ft GSD where there is limited
contrast between the rafters and the underlying flooring. Contrast between the
blue water and the white pool-house rafters, however, suggests that where con-
struction has been completed and subsequent roof damage has occurred, there
may be sufficient contrast to distinguish rafters from the floor-covering material
below them. This may enable successful determination at 1-ft GSD of whether
the rafters are substantially intact.
Area 2 sites
The area 2 mosaic (Figure 7) shows the remaining two sites, designated by a
yellow boundary marker. Site 4 showed various stages in the construction of a
commercial building, from land clearing to foundation pouring, from wall and
roof framing to partial plywood roof sheathing, and from plywood and tarpaper
roof covering to finished shingled roofing. Site 5 is located in a sports-complex
region that contains a mix of vegetation types, including grasses, bushes, and
trees.
Commercial building rafters
The roof rafters and plywood sheathing of the new building at site 4 are
visible at all three resolutions with, as expected, the most detail at 8-in. GSD.
When the GSD is larger than 8 in., it is difficult to distinguish individual rafters,
but that may be an artifact of new construction (see Conclusions, below). Figure
8 shows images of the exposed roof rafters at site 4 within area 2. The figures
progress from coarse (2-ft) to medium (1-ft) to fine (8-in.) GSD images.
Scatter plots
An image-processing approach that might lead to an automatic process of
distinguishing between intact roofs and damaged roofs was also attempted.
Scatter plots of band 1 (visible red) vs. band 2 (visible green) of a roof under
construction and a completed, intact roof were displayed with ENVI (ENVI
2000). The plot for the roof under construction (proxy damaged roof) was
expected to show more variability in reflectance due to chaos (a plethora of
colors) than the intact roof. The intact roof was expected to show only a rela-
tively invariant color-tone because of the single-color shingles and brightness
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