*3.3. Procedure of the Tracking Method Based on an IMMEKF Combined with an ELM*

The procedure of the target tracking method based on an IMMEKF combined with an ELM is shown in Figure 4. Track segments are obtained by the IMMEKF when tracking the maneuvering target using the stereoscopic HFSWR data, and simultaneously, the ELM decides whether the newly obtained track segment associates with the former segment via feature classification. In this way, the method can achieve long-term continuous tracking of the vessel target.

**Figure 4.** Flow graph of the continuous tracking method based on IMMEKF combined with ELM.

#### **4. Experiment Results**
