Supporting Studies

Other Sensors Study

The supporting study into the use of other sensors defined a top level set of functionalities, as shown below, the purpose of which was to provide a general set of criteria against which different sensors could be assessed for down selection for more in depth analysis. This was required due to the large number of sensors types that exist.

Additional Sensors Functional Categories

The results of the top level systems design trade study showed that none of the individual sensors considered were currently capable of providing all the functionality required by SUBITO. Furthermore some other sensor technologies are currently too immature to provide benefit within the SUBITO timescales. With the exception of a Hyperspectral system any sensor used would have to be used in conjunction with existing CCTV in order to be effective in detecting unattended baggage.

The use of a particular sensor within a SUBITO type system depends on the nature of the information they can provide. Some sensors, such as explosive threat identification systems would provide supporting information but would not provide a significant improvement on the primary functions of SUBITO obtained using CCTV.

SUBITO Sensor / Functional hierarchy

The figure above summarises the findings of the study. Here the SUBITO functional hierarchy leading to the system providing an alarm event to the operator is shown. The types of additional sensors investigated are mapped to this hierarchy, identifying the types of information and event that each can supply.

The SUBITO architecture takes into account the output of the additional sensor studies and makes provision for the inclusion of other sensors in future development, however for the final demonstration it was not considered likely that the identified sensors could be sourced and integrated alongside the core technologies.

Distributed System

In parallel to the additional sensors investigation a study into distributed system architecture was undertaken which considered the practical aspects of working with a distributed system to perform the SUBITO task. The general aims were to identify the appropriate structure, carry out a cost-benefit analysis and define the basic requirements for this type of distributed system.

In a centralized system, such as the system context shown in the system definition, where high resolution cameras are used, and data is generally received in a compressed format. This data must be decompressed prior to analysis which places a heavy loading operation on the processing, but the cost of using specialised hardware to ease the loading on the central processor is typically not very critical.

In comparison for a distributed system, low cost, high performance processors and dedicated decompression modules are required leading to considerably increased costs.

From the wireless transmission tests performed in the study, it is clear that for a distributed network of surveillance processors located in crowded areas where there are potentially many other Wireless Local Area Network (WLAN) users, the possibility exists for the communication links to deteriorate (either through heavy load of users or deliberate jamming). This is intolerable for potentially safety critical system.

The use of high gain directional antennas within the system design, could improve this situation for fixed long distance links; however, for such links a high level of external RF noise is possible which may interfere with system performance.

The study concluded that both compressed and decompressed image formats are need within surveillance systems. The compression/decompression process using software to achieve the modern compression standards overloads typical consumer Personal Computer (PC) processors.

In terms of the architecture for the SUBITO project and demonstration, no wireless or distributed processing was included due to the potential impacts on system performance and increased work in maintaining system security.

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