Merging can take place at different levels, with a trade-off between accuracy and complexity:
- Data level: combining raw measurements. Highest accuracy, but the heaviest processing and the strictest demands on time and position registration.
- Feature level: merging derived characteristics (velocity, micro-Doppler, spectrum, shape).
- Decision level: each sensor decides for itself ("drone, yes/no"), after which the outcomes are voted on. Robust and simple, but you lose detail.