基于多轨延迟-多普勒图的海面目标定位模糊去除

随着导航反射信号技术在海洋遥感领域的发展,利用星载延迟-多普勒图（Delay-Doppler Map, DDM）进行海面目标探测成为如今热门研究问题。但由于DDM上相同时延和多普勒点对应的空间区域具有不唯一性,导致出现真假目标定位模糊的问题。本文利用多颗卫星下不同镜反射点(Specular Point, SP)对应的DDM联合处理去除假目标。首先计算出目标相对各自SP的距离,然后以某个SP为原点将所有目标全部统一到一个坐标系内,通过真目标聚集来去除假目标;最后通过经纬度与距离关系求得目标最终地理位置。采用Cyclone GNSS(CYGNSS)星座的DDM数据开展验证实验,结果表明：利用多星轨迹DDM的海面目标探测时,真目标会聚集,假目标会分散;计算的目标最终位置与同时间段下“南海四号”钻井平台工作地点变化规律一致,误差小于1.5km,表明本文方法能有效解决海面目标定位模糊问题。

Removing location ambiguous of sea surface target based on multi-orbit DDM

With the development of navigation and reflection signal technology in the field of Marine remote sensing, the application of satellite-borne Delay-Doppler Map (DDM) to target detection on the sea surface has become a hot research issue. However, due to the non-uniqueness of the same time delay and the corresponding space region of Doppler points in DDM, the problem of location ambiguous of true and false targets arises. In this paper, the combined processing of DDM corresponding to different Specular points (SP) under multiple satellites was used to remove false targets. Firstly, the distance between the target and their respective SP was calculated, and then all the targets were unified in one coordinate system with one SP as the origin, and the false targets were removed by the aggregation of true targets. Finally, the final geographical position of the target was obtained through the relationship between longitude, latitude and distance. In this paper, the DDM data of Cyclone GNSS constellation was used to carry out verification experiments. The results show that the true target will gather and the false target will disperse when the multi-star trajectory DDM is used to detect the sea surface target. The calculated final position of the target is consistent with the variation law of the working place of "Nan Hai No.4" drilling platform in the same period of time, and the error is less than 1.5km, which indicates that the proposed method can effectively solve the problem of location ambiguous on the sea surface target.