Chart Navigation & Plotting · Chart Basics
Charted depths (soundings) on a U.S. chart are referenced to which tidal datum?
- AMean high water
- BMean sea level
- CMean lower low water✓ Correct
- DHighest astronomical tide
Explanation
U.S. soundings are referenced to mean lower low water (MLLW), a conservative datum that makes charted depths the depth you can usually count on. The actual depth equals the charted sounding plus the height of tide at that moment.
Authority: Chart No. 1; NOAA charting standards
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