A false alert is a Cospas-Sarsat distress alert message that is forwarded to SAR authorities, but which does not correspond to an actual distress situation. Every false alert represents a waste of valuable SAR resources since each must be investigated by SAR services before the case can be closed. Additionally, a high false alert rate causes SAR services to question the reliability and integrity of all Cospas-Sarsat data. Investigation into false alerts revealed the following typical causes:
- beacon mishandling (e.g., improper testing, storage or disposal);
- beacon malfunctions (e.g., faulty activation switch, water ingress, or electronics malfunction);
- mounting failures;
- extreme environmental conditions.
In view of their impact, Cospas-Sarsat has developed a comprehensive false alert monitoring and reporting programme, which is described in the document C/S A.003 (System monitoring and reporting). This programme provides guidance to Participants for tracking and reporting the number and the causes of false alerts. The information obtained from this programme is reported to international organisations (i.e., IMO) to seek their assistance in reducing the number of false alerts through education programmes. It is also used by Cospas-Sarsat for developing enhancements to the System that help reduce the number and / or impact of false alerts on SAR services.
Cospas-Sarsat currently reports two false alert rates:
- the ratio of false alerts to the total number of alerts transmitted to SAR services, i.e. the “SAR” false alert rate;
- the ratio of false alerts to the estimated beacon population, i.e. the “beacon” false alert rate.
The SAR false alert rate is a measure of the impact of false alerts on SAR services. However, because this rate is traditionally high (around 95% or more) in all automatic alerting systems, a large reduction in the number of false alerts would translate into a much smaller reduction of the rate. Therefore, a better appreciation of the impact of false alerts can be derived using the ratio of actual distress alerts to the total number of alerts, e.g.:
- SAR false alert rate of 98% = one real distress for 50 Cospas-Sarsat alerts
- SAR false alert rate of 96% = one real distress for 25 Cospas-Sarsat alerts
- SAR false alert rate of 90% = one real distress for 10 Cospas-Sarsat alerts
A reduction of the SAR false alert rate from 98% to 90% would correspond to a reduction by a factor 5 of the actual number of false alerts. The beacon false alert rate is independent of the size of the population. It is a good indication of beacon performance and provides a good basis for tracking global trends in the System. It can also be used to characterise the performance of a particular beacon type or model.