Correlating optical and radar imagery with S-AIS signatures enables the end-user to rapidly identify all types of vessel. A great strength of S-AIS is the ease with which it can be correlated with additional information from other sources such as radar, optical, ESM, and more SAR related tools such as GMDSS SARSAT and AMVER. Satellite-based radar and other sources can contribute to maritime surveillance by detecting all vessels in specific maritime areas of interest, a particularly useful attribute when trying to co-ordinate a long-range rescue effort or when dealing with VTS issues.