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The .nullcad Archive

NullCad projects are saved as a ZIP-based archive format (.nullcad), containing:

manifest.json     — project metadata, resource index, phase status
document/         — geometry, layers, document metadata, comparisons,
                     selection sets
operations/       — complete operation history
state/            — camera positions, snap config, application settings
resources/        — embedded files (PDFs, images, field data)

Why an archive, not a single JSON file?

Bundling resources (reference PDFs, images, field data files) directly in the project file means a .nullcad file is fully self-contained — moving, copying, or archiving one file preserves everything needed to reopen the project exactly as it was, without broken links to external files.

Legacy JSON format

Older NullCad projects were saved as plain JSON. These are automatically detected and migrated on load — you don’t need to convert them manually.

Operation history as audit trail

The operations/ directory holds the complete, append-only operation log for the document (see Operation System) — every mutation ever made, in order, including the ones later undone. This gives every .nullcad file a full audit trail of how the survey model was built, not just its final state.

Resource management

Plans, photos, and field data files can be embedded directly in the project archive under resources/ and referenced from geometry or annotations — e.g. a PlanImage geometry object placing a reference PDF page in world space, or a resource attached to a point for field documentation.

  • .ncweb — a separate, purpose-built bundle for the companion web viewer. See Web Viewer Bundle.