TeRA Troubleshooting

I Think the Threat Score Is Too Low or Too High

Background on How TeRA Scores Threat

It is important to acknowledge that TeRA provides a particular perspective and method to measure threat. Your own perception of the threat level may be influenced by factors, considerations and weightings that are very different to those used by TeRA. For this reason, you may feel that the threat score provided by TeRA is "too high" or "too low" relative to your own assessment of site. TeRA employs methods that are different to those that might be performed by a human assessor, and that is its main strength: it thinks and approaches the problem of assessing terrorism risk in a different way that minimises human bias. For this reason, you may instinctively disagree with the results produced by TeRA. TeRA is not intended to override your own perception or assessment and should not be used as such. TeRA is designed to provide an additional perspective, providing data points and insights that may enhance your own assessment of the situation. The following may provide additional insight on how TERA behaves and performs its scoring, which may also provide further insight on why you received a score that was "too high" or "too low".

Why Your Score May Be "Too High"

The threat score is determined by applying a contra-harmonic mean to the site risk score and background risk score. A contra-harmonic mean is used because it allows the overall threat score to moderate between potentially large differences between the site risk score and background risk score. For example, a site may have a high site risk score because it is a very prominent or iconic site but be located in an area which has a historically low amount of terrorist activity. The overall risk score for this site will still be high as the contra-harmonic mean will take the higher value of the site risk score as the dominant feature. Another site may be located in an area which historically high levels of terrorist activity, but not be particularly prominent. In this case, the fact that the site is located in a high-risk area becomes the dominant factor in its overall threat score, so this becomes the dominant feature. In context of TeRA, the contra-harmonic mean therefore behaves in a manner that helps minimise false negatives versus a harmonic mean which would minimise false positives. Simply put, TeRA will tend to overscore threat rather than underscore it.

Why Your Score Might Be "Too Low"

The dominant cause of threat scores being seen as "too low" is due to the reference terms used in the online search that in turn drives the site risk score. The reference name/terms used may have been too specific, or configured in a way that overly restricts the scope of the online search performed.

I Disagree with the Recommended Level of Security

The recommended level of security is only meant to be exactly that - a recommendation directly based on the threat score, with each threat score level mapping directly to a recommended level of security. The recommended level of security may not be appropriate for your specific circumstances but can provide a guide for what security measures should be considered.

Sites Are Missing from the Surrounding Area Search

The analysis performed to identify surrounding sites is based on open-source data. Sites may be missing from the search as a result of three main issues:

• The site has not yet been mapped
• The site has been deliberately removed (due to security or privacy reasons)
• The site is incorrectly or inaccurately labelled as something else (e.g. a police station labelled as a office building)

TeRA has several measures in place to try and minimise these issues with open-source and crowd-sourced data, however these are also issues which are inherent to the use of this type of data.