Heights, such as those for bridges, are typically given in feet above which reference point?

The correct choice for the reference point used when stating the heights of structures like bridges is Mean Sea Level. This reference point is based on the average height of the sea surface over a long period of time and is commonly used in navigation, construction, and various engineering applications. Heights given above this level provide a consistent and widely accepted standard, which is essential for safety and operational planning, especially in maritime contexts.

When structures like bridges are measured in relation to Mean Sea Level, it ensures that navigators have the most accurate and reliable information regarding clearance, thus preventing potential collisions with vessels. If a height were referenced from mean high water or mean low water, it would not provide a uniform measurement for all tidal conditions, potentially leading to confusion and unsafe navigation.

Although Chart Datum also serves as a reference for tides and depths, it is generally used in the context of hydrographic surveying and nautical charts to indicate the lowest level of tidal water. This reference is not typically applied when reporting the height of structures like bridges.