SLAMorris Final Thesis After Corrections.pdf - Cranfield University

number of fragments which contain only image data. The last fragment of the
image can be identified by working out the position of the last image data byte
relative to the start of the fragment; this is shown in figure 9.6. Secondly
assuming the visual thumbnail was written and any subsequent changes to the
visual thumbnail resulted in a completely new visual thumbnail being generated
which replaces the subrecord it can be assumed the chances of fragmentation
are small; therefore the first step in image fragment reassembly is to identify if
any of the fragments available would have been located next to the
reassembled data on the disk. If a candidate fragment is next to the last
fragment in the reassembled sequence it is likely to be the next fragment;
therefore by first attempting to reassemble potential chains on the disk it is
possible to minimise reassembly resources.
Figure 9-6: Calculations for image reassembly
If trying the fragments located close to the existing sequence did not provide a
valid file sequence it would be necessary to try other techniques. An option for
reassembling the image fragments for a known size of image data is to try every
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