The photoNumber is the label crews use to refer to a shot in field notes, on photo boards, and in reports — values like "2026-014" or "P-0312". Relic guarantees this number is unique within a single project, so no two photographs in the same dig can share it, while different projects are free to reuse the same numbering scheme. Because the uniqueness is scoped to the project, the photoNumber together with the project is what unambiguously identifies any one image in the catalogue.
Technical section
Data model, API, and internals — visible to developers.