INT 1 · I 15
Drying height
Depths & contoursCore
An underlined figure is a height above chart datum, not a depth.
What it means
An underlined sounding-style figure marks ground that uncovers. An underlined 2₄ means the feature dries 2.4 units above chart datum.
Why it matters
Add the predicted height of tide and then subtract the drying height to estimate water over the feature, allowing for weather, squat, and uncertainty.