Page 596 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

With all of the difficulties associated with these technologies, with proper training and imple- mentation they remain powerful tools for accomplishing port security tasks.
21.4.7 Techniques for accomplishing port security tasks
ROV-based underwater port security tasks involve two broad categories of inspections:
1. Identification of targets located by other means 2. Clearing an inspection area of suspicious items
It is possible to discover an item of interest while making random searches of an area. However, it has been found to be of marginal benefit to conduct unstructured searches of suspect areas. As water visibility decreases, a high degree of certainty that an area of interest has been cleared, with all suspicious items discovered, becomes increasingly difficult, as does positive navi- gation through the search area. In order to construct a maximum risk/benefit model of search time covering the high-risk exposure, a combination of tools and techniques must be used to achieve best results. These are discussed below.
21.4.7.1 Hull searches
The highest risk sections of commercial and military seagoing vessel hulls are isolated to a limited set of landmarks located on the hulls of these vessels. These targets can be located and checked in a relatively short time, thereby quickly eliminating the high-risk areas. Later, a search pattern can be implemented to image a specified percentage of the hull area.
One hundred percent visual hull coverage is exceedingly difficult to achieve due to navigational considerations as well as environmental factors, with the time-requirement curve turning nearly vertical as the water visibility nears zero (Figure 21.29). Experience has shown that the 80/20 rule applies in
Visibility/time to complete
FIGURE 21.29
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Visibility in feet
21.4 Homeland security 595
Visibility versus time to complete inspection task.
Time to complete