Target Monitoring Using Small-Aperture Compact High-Frequency Surface Wave Radar Figure 13. Tracking result in the range-velocity coordinates. (a) Target 1. (b) Target 2. Figure 14. Parameter distribution over time. (a) Target 1. (b) Target 2. curved. Moreover, it can be founded from Figure 13 that both the radial velocity and the range of the two tracks detected using three channels are close to those detected using eight channels, and their difference can be neglected. Therefore, only the radial velocity and range of the two tracks using three channels were analyzed. As seen from Figure 14a, the range of Target 1 steadily increased, while its radial velocity relative to the radar station var28 ied greatly because of drastic changes in heading. Despite this, the target can still be tracked by HFSWR, and the retrieved radical velocity has smaller deviations compared with the in situ AIS data. Figure 15 shows the parameters' deviations and their distance between HF radar and AIS over time for the two targets, and Figure 16 shows the distance histogram between HF radar detected points and AIS positions. As seen from Figures 15 and 16, the devi- IEEE A&E SYSTEMS MAGAZINE MARCH 2018