Hydrographic surveying: soundings (measured depths) are required for which of the following purposes?

Introduction / Context:
Soundings are the backbone of safe navigation and marine construction. By mapping underwater depths, engineers and mariners can plan channels, analyze sediment movement, and design durable port structures.

Given Data / Assumptions:

• Measured depths referenced to a suitable chart datum.
• Temporal changes due to scour/siltation are relevant.
• Construction requires detailed bathymetric inputs.

Concept / Approach:
Bathymetry underpins chart compilation, sediment studies, and design. Repeated surveys can identify morphological changes; higher-density surveys support construction staging and quantity calculations (e.g., dredging).

Step-by-Step Solution:
Relate each listed purpose to standard hydrographic deliverables (charts, sediment maps, construction drawings).Recognize that all three uses are core applications of soundings.

Verification / Alternative check:
Review of port development projects shows soundings supporting navigation, maintenance dredging, and works planning.

Why Other Options Are Wrong:

• Limiting soundings to a single purpose undervalues their broad role in coastal and marine engineering.

Common Pitfalls:

• Using outdated bathymetry for navigation or design, ignoring recent siltation/scour.

Final Answer:
all the above.