Cross correlation (correlating a signal with another) can be used to identify a signal by comparison with a library of known reference signals.
The diagram shows how the unknown signal can be identified.
- A copy of a known reference signal is correlated with the unknown signal.
- The correlation will be high if the reference is similar to the unknown signal.
- The unknown signal is correlated with a number of known reference functions.
- A large value for correlation shows the degree of similarity to the reference.
- The largest value for correlation is the most likely match.
Cross correlation is one way in which sonar can identify different types of vessel.
- Each vessel has a unique sonar 'signature'.
- The sonar system has a library of pre-recorded echoes from different vessels.
- An unknown sonar echo is correlated with a library of reference echoes.
- The largest correlation is the most likely match.