In immersion B-scan imaging, depth information is most accurately represented by which description?

• A. Height of indication from the hole bottom and depth from the entry surface
• B. Plan view of the block
• C. Top surface only
• D. Bottom surface only

Answer: (A)

In immersion B-scan imaging, the meaningful measure of where a flaw lies is its position with respect to reference planes, not just a single surface view. The depth into the material is typically described from the entry surface, which tells you how far under the surface the reflector is. But when you’re inspecting features inside a hole or bore, you also need a second coordinate to locate the reflector along the hole itself. Describing the indication’s height from the hole bottom along with its depth from the entry surface gives a complete two-dimensional position within the bore, allowing an accurate determination of where the flaw sits inside the component.

The other descriptions miss this depth context. A plan view or surface-only references don’t specify how deep the defect is, and focusing on just the top or bottom surface doesn’t provide the necessary depth information.