Elevation reference datum: In civil/landform drawings and mapping practice, are elevations commonly referenced to Mean Sea Level (MSL) or an equivalent vertical datum?

Introduction / Context:
Elevations must be comparable across time and projects. Standard practice is to reference vertical measurements to Mean Sea Level (MSL) or an officially defined vertical datum (e.g., NAVD 88), ensuring consistency across surveys and drawings.

Given Data / Assumptions:

• Projects require consistent elevation references for design and construction.
• Survey control networks provide benchmarks tied to vertical datums.
• Notation on drawings typically declares the vertical datum used.

Concept / Approach:
Using MSL or a recognized vertical datum allows elevations from different surveys to align. Local temporary benchmarks can be used, but they are established from, and documented relative to, the official datum to preserve traceability. This enables accurate grading, drainage design, and flood assessments.

Step-by-Step Solution:

Verification / Alternative check:
Comparing two surveys on the same site: if both reference the same datum, elevations match; if not, a datum shift must be applied to reconcile them, demonstrating why common datum usage is standard practice.

Why Other Options Are Wrong:

• Random local references (option B) undermine comparability.
• Scale dependency (option C) is irrelevant.
• Limiting to coastal projects (option D) is incorrect; inland work also uses vertical datums.
• Claiming no datum is used (option E) contradicts engineering standards.

Common Pitfalls:
Ignoring the vertical datum note; mixing datums without applying shifts; assuming “MSL” generically without specifying the exact datum realization.

Final Answer:
Correct: elevations are commonly tied to MSL or an official vertical datum