Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Visual and Verbal Communication (hierarchy name)
4. Information Forms (hierarchy name)
5. information forms (objects)
6. document genres
7. [documents by function]
8. [identifying markings and symbols]

Anotations

Scope note:

Marks on a fixed and enduring object, indicating its elevation above sea level and serving as a reference in topographic surveys and tidal observations. In a more general sense, the term may also refer to any point of reference from which measurements may be made.