Modern Electronic Chart Display and Information Systems (ECDIS) rely on GNSS (GPS) positioning, which is natively WGS84. However, many Electronic Navigational Charts (ENCs) are digitized from legacy paper charts based on local datums (e.g., Tokyo Datum, ED50, Indian 1960) where the transformation parameters to WGS84 are undefined or inaccurate.
⚠️ Warning: Raw GPS to CAD Coordinate Discrepancy
Combining uncorrected WGS84 drone data with NAD83 site plans creates a structural shift of 1-2 meters. Review the massive legal implications of this error.
Explore Boundary Dispute Liability →Maritime safety notices explicitly warn that some ENCs "cannot be accurately referenced to WGS84 Datum." In these regions, the position of the ship on the chart may be offset by 100 meters to several kilometers from its actual GNSS location.
Consequence: A vessel appearing safe in deep water on the ECDIS screen may effectively be 100m closer to a reef or shoal in reality.
For marine surveyors and hydrographers, failure to account for these "undefined shifts" creates significant liability exposure.
Scenario: A navigator relies solely on GNSS overlays on a non-WGS84 ENC, ignoring "Caution Areas" or "Accuracy" attributes.
Legal Outcome: Courts rarely accept "chart error" as a defense if warnings were present. This constitutes negligent navigation, potentially voiding Hull & Machinery (H&M) insurance policies under "unseaworthiness" clauses.
Risk: Producing bathymetric surveys without explicit datum metadata (WGS84 vs LAT vs Local) breaches the International Hydrographic Organization (IHO) S-44 Standards. If a dredging operation creates a hazard based on your ambiguous survey, your Professional Indemnity (PI) insurance faces the claim for the resulting grounding.