iterations of pairwise stitching were then performed using the
new sets of stitched, paired images. This process continued
until the image pairs were exhausted, thus generating the final,
stitched, perspective image. As seen in Figure 6, there are
log
2
(
n
) stitches performed for
n
images in the parallel processing
method, compared to
n
−1 stitches if the processing method was
sequential, as shown in Figure 7. While both approaches will
result in a mosaicked image, the pairwise matching method uti-
lizes fewer computational resources and due to requiring fewer
steps, errors accumulated during image resampling at each step
are reduced, thereby improving the final image quality.
Several potential manmade objects were identified in the
video by members of the team familiar with the model of
aircraft that was the subject of the search as well as engineers,
marine biologists, and a coral ecologist. Front and rear land-
ing gear were tentatively identified, along with an obviously
man-made rope. Figure 8 shows the entire scene of interest
containing the proposed front and rear landing gears, and the
rope, in a single perspective image. This figure was stitched
from 64 sampled frames of the video, which never contained
the front landing gear and the rope within a single frame.
In the following sections, we assess the likelihood that
these two pieces of debris were actually the landing gear from
the crashed plane.
Figure 5. The timestamp was removed and replaced with scene
data during the masking and mosaicking process, allowing an
unobstructed view of the circular object partially masked by the
time stamp in the upper image.
Figure 6. The pairwise matching, transformation and stitching
process for
n
images completes in T(log
2
(
n
)) time. Three iterations
from eight images are shown in this example.
Figure 7. For comparison, sequential matching requires T(
n
−1)
time. Seven iterations from eight images are shown in this example.
Figure 8. Scaled stitched composite from 64 images showing
debris field showing the proposed front and rear landing gear in a
single perspective image.
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
March 2016
227
