With the increasing development of GPS-equipped mobile devices such as smart phones and vehicle navigation systems, the trajectories containing valuable spatiotemporal information are recorded. Typically, plenty of trajectory records are generated and stored, making the device memory suffer a heavy storage pressure. Thus, it is a vital issue to compress the trajectories. The trajectory semantics are usually ignored or reduced in traditional trajectory compression techniques. In addition, most of existing trajectory compression algorithms only concern the position errors rather than the velocity errors of trajectories. This paper proposes a velocity-preserving trajectory compression algorithm based on retrace point detection (VPTC-RP) that can compress a set of trajectories by removing unnecessary redundancy points, while the skeleton of these trajectories is maintained as much as possible. In VPTC-RP, the retrace points and the velocity errors are taken to reflect the speeds and directions attached with the points. VPTC-RP first determines the retrace points based on the changed movement directions, and then, the retrace points are extracted from the original trajectories. Especially, the retrace points are put in a buffer, and the subtrajectories in the buffer are compressed according to the measured velocity errors. Simulations are carried out on the Geolife trajectory dataset, and the simulation results indicate that VPTC-RP can achieve a preferable tradeoff among the compression error, compression ratio, and running time.

中文翻译：

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基于回溯点检测的保速轨迹压缩

随着配备 GPS 的移动设备（如智能手机和车辆导航系统）的不断发展，包含有价值的时空信息的轨迹被记录下来。通常情况下，会生成并存储大量的轨迹记录，使得设备内存承受很大的存储压力。因此，压缩轨迹是一个至关重要的问题。在传统的轨迹压缩技术中，轨迹语义通常被忽略或减少。此外，大多数现有的轨迹压缩算法只关注位置误差而不是轨迹的速度误差。本文提出了一种基于回溯点检测的保速轨迹压缩算法（VPTC-RP），可以通过去除不必要的冗余点来压缩一组轨迹，同时尽可能保持这些轨迹的骨架。在 VPTC-RP 中，回扫点和速度误差被用来反映与这些点相连的速度和方向。VPTC-RP 首先根据改变的运动方向确定回扫点，然后从原始轨迹中提取回扫点。特别是将回扫点放入缓冲区，并根据测得的速度误差压缩缓冲区中的子轨迹。在 Geolife 轨迹数据集上进行了仿真，仿真结果表明 VPTC-RP 可以在压缩误差、压缩率和运行时间之间取得较好的权衡。回溯点和速度误差被用来反映与这些点相连的速度和方向。VPTC-RP 首先根据改变的运动方向确定回扫点，然后从原始轨迹中提取回扫点。特别是将回扫点放入缓冲区，并根据测得的速度误差压缩缓冲区中的子轨迹。在 Geolife 轨迹数据集上进行了仿真，仿真结果表明 VPTC-RP 可以在压缩误差、压缩率和运行时间之间取得较好的权衡。回溯点和速度误差被用来反映与这些点相连的速度和方向。VPTC-RP 首先根据改变的运动方向确定回扫点，然后从原始轨迹中提取回扫点。特别是将回扫点放入缓冲区，并根据测得的速度误差压缩缓冲区中的子轨迹。在 Geolife 轨迹数据集上进行了仿真，仿真结果表明 VPTC-RP 可以在压缩误差、压缩率和运行时间之间取得较好的权衡。回扫点放入缓冲区，缓冲区中的子轨迹根据测得的速度误差进行压缩。在 Geolife 轨迹数据集上进行了仿真，仿真结果表明 VPTC-RP 可以在压缩误差、压缩率和运行时间之间取得较好的权衡。回扫点放入缓冲区，缓冲区中的子轨迹根据测得的速度误差进行压缩。在 Geolife 轨迹数据集上进行了仿真，仿真结果表明 VPTC-RP 可以在压缩误差、压缩率和运行时间之间取得较好的权衡。