Which measurement uses mean high water as...

Question 1 / 2707066636ee928f7522a1c519bb3

Question 1 of 2707066636ee928f7522a1c519bb3

Which measurement uses mean high water as the reference plane?

Question 1 of 27070

Which measurement uses mean high water as the reference plane?

🔍 Key Concepts

• Chart datums used for depths vs. heights on U.S. nautical charts • Difference between mean lower low water (MLLW) and mean high water (MHW) • What vertical features (like lights, bridges, cliffs) need a height measured from a typical high-water level

💭 Think About

• Ask yourself: when navigating, which information needs to be safely above the highest expected water level, and which needs to ensure clearance at the lowest? • Consider which chart measurements must remain conservative for under-keel clearance versus for overhead clearance or visibility of aids to navigation. • Think about whether all vertical measurements share the same reference, or if depths and heights use different tidal datums.

✅ Before You Answer

• Identify which datum U.S. charts normally use for soundings/depths (hint: it is a low-water datum). • Identify which datum is typically used for heights of lights and other elevated features relevant to visibility and clearances. • Confirm whether the word "all" in one of the options can really be correct, given the different safety needs for depths versus heights.

Question 1 of 27070

Which measurement uses mean high water as the reference plane?

Heights above water of land features such as lights

Soundings on the East and West Coasts

Water depths on the East Coast only

All vertical measurements on charts

Question 1 / 2707066636ee928f7522a1c519bb3

Question 1 of 2707066636ee928f7522a1c519bb3

Which measurement uses mean high water as the reference plane?

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Question 1 of 27070

Which measurement uses mean high water as the reference plane?