METHODOLOGY
1. AIS Data and Preprocessing
The Automatic Identification System (AIS) is mandatory for vessels > 300 GT under IMO SOLAS. Class A transponders transmit every 2-12 seconds when the vessel is underway.
Fields used:
MMSI, timestamp, lat, lon, SOG, COG, heading, navstat, vessel_typeData Quality Issues
- GPS noise: ±10m typical, ±100m in poor conditions
- Timestamp gaps: normal in high-traffic areas (VHF congestion)
- Erroneous MMSI: some vessels transmit invalid identifiers
- Spoofing: deliberately false positions (active research area)
Preprocessing Pipeline
1. Remove invalid MMSI (length ≠ 9)
2. Filter SOG > 50 kn (physically impossible)
3. Remove jump points > 30 kn implied speed
4. Linear interpolation for gaps < 5 min
5. Segment trajectories at gaps > 30 min
2. ML Anomaly Detection
Feature Vector per vessel-day
mean_sog, std_sog
Speed by vessel type
cog_change_rate
Turning behavior
total_gap_minutes
Total AIS gap time while SOG > 0.5
loitering_index
Fraction of time within 2nm
destination_consistency
Cosine similarity with declared destination
route_deviation
Hausdorff distance from DBSCAN cluster
Model: Isolation Forest
IsolationForest(n_estimators=200, contamination=0.02, random_state=42)Trained on Danish Maritime Authority open dataset (2022-2023, 4.2M vessel-days). Domain adaptation using CORAL for Aegean vs Baltic.
Performance (DMA test set)
0.71
Precision
0.62
Recall
0.66
F1
3. Data Gateway and Production Flow
AISHub
Feed
→
Pre-process
Clean
→
Features
Extract
→
IF Score
Model
→
Rules
Overlay
→
Frontend
Display
Data Sources
| Data | Source | Access | Use |
|---|---|---|---|
| AIS positions | AISHub | Free | Live feed |
| Historical AIS | Danish Maritime Authority | Open | Model training |
| Marine Protected Areas | EEA Natura 2000 | CC-BY | Fishing zones |
| Bathymetry | GEBCO 2024 | Open | Depth check |
| Port data | Piraeus Port Authority | Public | Port reference |
Demo: Static pre-computed snapshot. In production: 10-minute refresh cycle.
References
• MDPI Marine Science 2023 - Isolation Forest + trajectory clustering
• ScienceDirect Ocean Engineering 2024 - STAD dynamic pattern clustering
• AIS-LLM Paper 2025 - Port of Piraeus anomaly detection benchmarks