卫星对地覆盖时间窗口实时计算方法

卫星对地覆盖时间窗口的高效计算能够有效地保障遥感卫星数据信息资源的管理与应用。为解决现有卫星对地覆盖时间窗口计算方法无法提供同时保证精度、效率和实时性的在线服务的问题,提出了一种实时卫星对地覆盖时间窗口计算服务方法。在时间窗口的通用计算方法基础上,建立了地面区域的扩充四至范围,通过判断卫星星下点与地面区域的扩充四至范围的空间关系来决定是否需要计算卫星对地覆盖区域;在卫星对地覆盖区域与地面区域空间关系发生变化时,通过双重时间步长策略提高计算效率和精度;使用流计算框架构建算法的实时在线服务。实验结果表明,与商业软件采用的跟踪传播算法对比,本文方法与其计算结果差异较小,均小于1 s,说明本文方法能够保证较高的计算精度;与传统跟踪传播算法相比,本文方法耗时大幅减少,实现了超过8倍的加速比。本文方法同时保证了精度、效率和实时性,能够满足不同场景下卫星对地覆盖时间窗口的计算需求。

A Real-Time Calculation Method for Satellite Ground Coverage Time Window

Efficient calculation of satellite ground coverage time window can guarantee the management and application of remote sensing satellite data. To solve the problem that existing algorithms for calculating the satellite ground coverage time window cannot provide real-time online service, which needs to guarantee the accuracy, efficiency and timeliness simultaneously, a real-time calculation service for satellite ground coverage time window was proposed in the present study. Based on the common calculation algorithm, the extended bounding box of ground area was established by extending a certain angle in four directions. By judging the spatial relationship between the sub-satellite point and the extended bounding box of ground area, whether the satellite ground coverage area should be calculated precisely was determined. If the sub-satellite point and the extended bounding box of the ground area were disjoint, there was no need to calculate the satellite ground coverage area, which avoids a large number of redundant calculation. Otherwise, the satellite ground coverage area was calculated and the spatial relationship between them was obtained. When the spatial relationship between the satellite ground coverage area and the ground area changed, there existed the start or stop time point of the satellite ground coverage time window, and two kinds of time steps were used to improve the calculation efficiency and accuracy of the time window. Finally, the distributed streaming calculation framework was used to build the real-time online service based on the proposed algorithm, and the topology of data processing was established to implement the algorithm. In the streaming calculation framework, the calculation processes of the satellite ground coverage time window are segmented and each result is integrated after the calculation processes are completed. The final calculation results can be stored in the database or used by different applications. Compared with the tracking propagation algorithm used by business software, our findings from the experimental results suggest that the difference between the proposed method and the business software is small, all of which are less than 1s, and that the real-time calculation service can ensure the accuracy, efficiency, and timeliness. Contrasting to the common tracking propagation algorithm, the real-time calculation service takes less time with an acceleration ratio of over 8 times. The proposed real-time calculation service can meet the requirements for calculating satellite ground coverage time window in terms of accuracy, efficiency, and timeliness in different scenarios.