Why Do Vessel Positions and Tracking Data Show Inaccuracies or Irregularities?
Introduction
Vessel tracking data is an essential resource for maritime operations and analytics. However, users may sometimes notice inaccuracies or irregularities in current positions, historical tracks, or vessel load conditions. These issues are not usually errors in the tracking platform but are caused by limitations in how signals are transmitted and received.
This article explains the main reasons why these discrepancies occur and how they affect the reliability of vessel tracking.
Causes of Missing or Inaccurate Data
1. Signal Gaps
Tracking platforms like MarineTraffic rely on vessels transmitting AIS (Automatic Identification System) signals. If a vessel stops sending AIS messages, its position will not update. The platform will only display the last known location until a new signal is received.
👉 This is the most common reason for missing or outdated vessel data.
2. AIS or GNSS Spoofing
In some cases, discrepancies are caused by spoofing – the deliberate transmission of false signals to mislead tracking systems. While relatively rare, spoofing can create irregularities in vessel positions. Platforms apply measures to detect and analyze these cases, which can also provide insights into unusual maritime activities.
3. Differences in Update Frequency
Not all vessels transmit position updates at the same rate. Variations depend on:
Signal strength and equipment – Weak signals or malfunctioning AIS transponders may cause irregular updates.
Environmental conditions – Weather, temperature, and signal interference can impact transmission quality.
Tracking method – Vessels near shore are picked up by terrestrial receivers, while vessels far offshore rely on satellites. Smaller vessels with class B transponders send weaker signals, so their updates may be less frequent.
As a result, two vessels in the same area may show position updates at very different intervals.
Conclusion
The accuracy of vessel tracking depends on multiple factors:
Continuous AIS transmissions
Signal strength and environmental conditions
Transponder functionality
Occasional irregularities such as spoofing
Understanding these challenges helps users interpret discrepancies without assuming a system error. In most cases, irregularities are a normal part of AIS-based tracking and resolve automatically once new signals are received.
💡 Tip: If you see outdated or irregular vessel data, it usually means the vessel has not transmitted a new AIS signal yet - not that the platform is malfunctioning.