Navigation General · Electronic Nav — ECDIS Overscale
Viewing an ENC at a larger scale than the data was compiled for (overscale/over-zoom) is dangerous because it:
- ACan make the chart look more detailed/precise than the underlying survey data justifies✓ Correct
- BImproves accuracy
- CChanges the datum
- DDisables alarms automatically
Explanation
Zooming in beyond the compilation scale does not add real detail; it can mislead the navigator into trusting positions to a precision the survey never supported. ECDIS displays an overscale indication, and the navigator should use the proper-scale cell.
Authority: IMO ECDIS performance standards; SOLAS V/19
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