Datum Level - Exactly What Is It? Essential in construction

The Vertical Datum: Or is that Mean Sea level?

Advanced GD&T Composite Position Tolerancing (step-by-step)What is it and why use it?Definition (one line): A composite positional tolerance uses a multi-segment feature control frame (usually two segments) to give separate and different control to (A) each feature in a pattern (tight, feature-to-feature) and (B) the pattern as a whole relative to datums (looser).When to choose it: use composite tolerancing when the relative position between features is critical (e.g., mating holes on a nameplat

What are examples of datum? - TimesMojo