Definition
Trajectory refers to the sequence of locations of moving objects (vehicles, personnel, goods) over time, usually consisting of longitude, latitude, timestamp, speed, direction, etc. Trajectory is the core data for logistics tracking, vehicle management, and full tracking, and can support applications such as trajectory playback, trajectory tracing, boundary alerts, and route analysis.
Trajectory data is collected by locators, logistics trackers, and other terminals, and uploaded to the platform via 4G/5G. Cross-border logistics and vehicles require one card for multiple countries to ensure full-process trajectory data reporting.
Technical Features and Architecture
Trajectory architecture includes: collection——positioning module (GPS/BeiDou), sampling frequency, event-triggered; transmission——4G/5G, differential transmission (only transmit change points) to save traffic; storage——time-series database, trajectory index; analysis——route planning, stay points, anomaly detection. To save traffic, data compression, thinning, and event-triggered reporting can be used. Combined with traceability chain, it can form traceable movement history.
In cross-border scenarios, trajectories need to support multiple time zones, maps of multiple countries, and multi-language annotations.
Application in IoT and cross-border scenarios
Trajectories are widely applied in: Logistics —— logistics tracking , container and parcel trajectories; Fleet ——vehicle trajectories, driving behavior analysis; Assets ——equipment and goods movement trajectories; Personnel ——fieldwork and inspection trajectories. Cross-border logistics, cross-border fleets, global asset tracking and other scenarios rely on trajectories to achieve full tracking and trajectory tracing .
SimtoLink provides trackers with coverage in over 200 countries, supporting stable trajectory data return to facilitate cross-border tracking scenarios.
A trajectory is a timed position sequence, not a road
In cross-border IoT, a trajectory is the position samples of one object arranged in time. A road, a lane, and a planned path are map data. They are not the trajectory this device measured. When samples are few, the sequence cannot uniquely determine how the object traveled in between. Storage should therefore keep the points, not only the geometry the platform drew by joining them. The geometry changes when the thinning algorithm changes. The original points should not change with it. Each point needs at least coordinates, the time of the fix, the source, and an accuracy indication. A point with no accuracy cannot be used to decide a boundary crossing. If speed and heading are inferred from neighboring points, label them as inferred. The device did not measure them directly.
The object identity decides who the sequence belongs to. Whether the identity is bound to the goods, the vehicle, or the trailer must be fixed before capture. Once the bound object changes, old and new points must not keep being joined into the same trajectory.
Conditions that keep the sequence continuous after roaming and late upload
Continuous here means a continuous time axis and a continuous identity, not a point every meter on the ground. Thinning by policy is allowed, and thinning must not delete a change of state, such as stationary becoming moving, or the source dropping from satellite to cell. Points may arrive late during roaming. A late point should be inserted in the sequence at the time of the fix, not appended at the end. Appending it at the end makes time run backward, and a later stop calculation treats a past point as a new position. A repeated late upload should be removed by the sample's own identity. Do not treat two samples as two places just because the coordinates are close.
Cross-border storage also has to decide where the sequence lives. A position sequence often reveals a recognizable pattern of activity. Do not copy every original point out of the country just because the display server is abroad. Sync only the stretches the business needs, and points whose accuracy has been reduced. Leave the original sequence in the agreed region.
Replacing the original points with the thinned polyline
Keeping only the thinned polyline, and deleting the original points, to save traffic or storage makes it impossible later to judge whether thinning removed a detour or a stop. Another error is to substitute a planned navigation route for the measured sequence. When the vehicle actually detours, the system still shows the recommended road. A third is to sort several days of points by coordinate instead of by time. A border crossing out and back is joined into a reversal that cannot be explained. Mixing coordinate frames makes the sequence jump near the border, and the jump distance is counted as speeding.
The retention rule should archive original points for their period. The display layer may thin them, and every alarm must be able to return to the original points for review. A polyline that cannot return to the original points cannot be the basis of a cross-border trip.
When the object loses the satellite signal inside a ship's hold or a tunnel, the sequence should insert a no-fix mark rather than join the two valid points on either side directly. A direct join draws that blank as a high-speed pass and shortens the stop. After the mark is restored, later calculations must skip the no-fix interval. Do not divide the distance between the two ends by the time difference and call that the true speed.
If thinning uses distance only and ignores a change of state, a long stop at a port is deleted down to two endpoints. If the display layer draws only distance and does not keep that time interval, the stop disappears from the trip. Thinning should at least keep the start and end of a stationary stretch. Otherwise a cross-border stop cannot be recovered from the sequence.