Hierarchy classification:

1. top of the aat hierarchies
2. Activities Facet
3. Processes and Techniques (hierarchy name)
4. [processes and techniques by specific type]
5. [image-making processes and techniques]
6. [photography and photographic processes and techniques]
7. photographic techniques
8. picture-taking techniques
9. [picture-taking techniques by radiation type]
10. radiography
11. tomography

Anotations

Scope note:

Technique used to create images of objects, structures, or other features located underground at relatively shallow depths, by bouncing sound waves off the features from several different positions, collecting and processing the signals to get a number of partial views, then focusing and combining these partial views to create a complete image; developed by Alan J. Witten between 1984 and 1987.