# WIA-EDU-023: Technical Specifications
## Cultural Heritage Digitization

**Version:** 1.0.0
**Last Updated:** 2025-01-26

---

## 1. Capture Technologies

### 1.1 Photogrammetry

**Workflow:**
1. Capture 50-300+ overlapping images
2. Camera calibration and lens correction
3. Structure from Motion (SfM) processing
4. Dense point cloud generation
5. Mesh reconstruction
6. Texture atlas creation

**Requirements:**
- Image overlap: 60-80% between adjacent photos
- Camera: 20MP+ with prime lens preferred
- Lighting: Even, diffuse, color-calibrated
- Scale references: Included in capture volume
- Color targets: X-Rite ColorChecker or equivalent

**Software:** Agisoft Metashape, RealityCapture, Meshroom (open source)

### 1.2 LiDAR Scanning

**Types:**

**Terrestrial Laser Scanning (TLS)**
- Range: 0.5m - 350m typical
- Accuracy: ±1mm to ±5mm
- Point acquisition: 50K-2M points/second
- Applications: Buildings, monuments, large artifacts

**Aerial LiDAR**
- Platform: UAV or aircraft
- Ground sampling: 5-20cm typical
- Applications: Archaeological sites, landscapes
- Requires: RTK/PPK GPS for georeferencing

**Structured Light**
- Range: 0.1m - 5m typical
- Accuracy: ±0.01mm to ±0.1mm
- Applications: Small-medium artifacts
- Advantages: High detail, fast capture

### 1.3 CT/X-Ray Imaging

**Applications:**
- Internal structure analysis
- Hidden content discovery
- Non-destructive examination
- Material composition study

**Parameters:**
- Resolution: Voxel size appropriate to object scale
- Energy levels: Adjusted for material density
- Reconstruction: DICOM format standard

---

## 2. Data Processing

### 2.1 Point Cloud Processing

**Cleaning:**
- Outlier removal (statistical or radius-based)
- Noise reduction
- Registration alignment (ICP algorithm)
- Ground plane normalization

**Decimation:**
- Voxel-grid filtering for uniform density
- Preserve edges and features
- Target density based on use case

**Formats:**
- **E57:** ASTM standard, widely supported
- **LAS/LAZ:** Compact, georeferencing support
- **PTS/XYZ:** Simple ASCII formats

### 2.2 Mesh Generation

**Algorithms:**
- Poisson reconstruction (watertight meshes)
- Ball-pivoting (preserves detail)
- Delaunay triangulation
- Screened Poisson (balance detail/smoothness)

**Optimization:**
- Decimation to target polygon count
- UV unwrapping for texturing
- Normal map baking from high-res
- LOD (Level of Detail) generation

**Quality Metrics:**
- Manifold edges (2 faces per edge)
- Inverted normals check
- Non-manifold vertices resolution
- Degenerate triangle removal

### 2.3 Texture Mapping

**Process:**
- UV atlas generation (minimal distortion)
- Photo projection and blending
- Color correction across seams
- Normal/roughness/metallic map baking

**Texture Specifications:**
- Format: PNG (lossless) or JPEG 2000
- Resolution: 4K-8K for medium objects
- Color space: sRGB for display, Adobe RGB for archival
- Mip-mapping: Generate for real-time rendering

---

## 3. File Format Specifications

### 3.1 glTF 2.0 (Recommended for Delivery)

**Advantages:**
- Royalty-free, open standard
- Efficient transmission (binary)
- PBR material support
- Animation support
- Wide software support

**Structure:**
```json
{
  "asset": {"version": "2.0"},
  "scene": 0,
  "scenes": [{"nodes": [0]}],
  "nodes": [{"mesh": 0}],
  "meshes": [{
    "primitives": [{
      "attributes": {"POSITION": 0, "NORMAL": 1, "TEXCOORD_0": 2},
      "indices": 3,
      "material": 0
    }]
  }],
  "materials": [{
    "pbrMetallicRoughness": {
      "baseColorTexture": {"index": 0},
      "metallicFactor": 0.0,
      "roughnessFactor": 1.0
    }
  }]
}
```

### 3.2 E57 (Point Cloud Archival)

- Compact binary format
- Supports RGB color, intensity
- Georeferencing metadata
- Multiple scans per file
- Open specification

### 3.3 X3D (Archival Standard)

- ISO/IEC 19775-1:2013
- XML-based scene graph
- Long-term preservation
- Multiple encodings (XML, binary, compressed)

---

## 4. Metadata Schemas

### 4.1 Technical Metadata

```xml
<technical>
  <acquisition>
    <method>photogrammetry</method>
    <equipment>
      <camera>
        <make>Canon</make>
        <model>EOS R5</model>
        <lens>RF 50mm f/1.2</lens>
        <resolution>45MP</resolution>
      </camera>
      <calibration>
        <date>2025-01-15</date>
        <method>checkerboard</method>
      </calibration>
    </equipment>
    <capture_date>2025-01-20</capture_date>
    <operator>Jane Smith</operator>
    <image_count>250</image_count>
    <lighting>Diffuse LED panels, 5500K</lighting>
  </acquisition>
  <processing>
    <software>
      <name>Agisoft Metashape</name>
      <version>2.0.1</version>
    </software>
    <steps>
      <align_photos quality="high" />
      <build_dense_cloud quality="medium" />
      <build_mesh source="dense_cloud" face_count="2000000" />
      <build_texture mapping="generic" blend="mosaic" size="8192" />
    </steps>
    <processing_date>2025-01-21</processing_date>
  </processing>
  <quality>
    <point_cloud_density>1000 points/mm²</point_cloud_density>
    <geometric_accuracy>±0.05mm</geometric_accuracy>
    <color_accuracy>ΔE 1.8</color_accuracy>
    <completeness>98.5%</completeness>
  </quality>
</technical>
```

### 4.2 Preservation Metadata (PREMIS)

Key elements:
- **Object:** Digital file characteristics
- **Event:** Actions performed on object
- **Agent:** Persons/systems performing events
- **Rights:** Copyright and access restrictions

### 4.3 Descriptive Metadata (Dublin Core + CIDOC-CRM)

See API reference for full schemas.

---

## 5. Storage Architecture

### 5.1 Repository Structure

```
repository/
├── masters/              # Preservation masters
│   ├── pointcloud/      # E57 files
│   ├── mesh/            # High-res OBJ/FBX
│   └── textures/        # Uncompressed TIFF
├── derivatives/         # Access copies
│   ├── web/            # glTF optimized
│   ├── ar/             # USDZ for iOS
│   └── thumbnails/     # Preview images
├── metadata/           # Sidecar files
│   ├── dublin_core/
│   ├── technical/
│   └── preservation/
└── documentation/      # Paradata
    ├── methodology/
    ├── reports/
    └── references/
```

### 5.2 Fixity Checking

**Checksums:**
- MD5 and SHA-256 for all files
- Stored in manifest files
- Automated verification schedule:
  - Hot storage: monthly
  - Warm storage: quarterly
  - Cold storage: annually

**Manifest Format (BagIt):**
```
bag-info.txt
bagit.txt
manifest-md5.txt
manifest-sha256.txt
data/
  ├── object001.glb
  ├── object001_metadata.xml
  └── object001_documentation.pdf
```

---

## 6. Quality Assurance

### 6.1 Validation Checklist

- ✅ Geometric accuracy verified with control measurements
- ✅ Mesh topology valid (manifold, no self-intersections)
- ✅ Textures properly aligned, no visible seams
- ✅ Color calibration verified against target
- ✅ File formats conform to specifications
- ✅ Metadata complete and validated against schema
- ✅ Checksums generated and verified
- ✅ Documentation complete

### 6.2 Peer Review

- Expert validation of reconstruction accuracy
- Community consultation where appropriate
- Accessibility testing with disabled users
- Technical review by preservation specialists

---

## 7. Web Delivery Optimization

### 7.1 Progressive Loading

1. Load low-poly preview mesh
2. Stream high-res geometry
3. Load compressed textures
4. Upgrade to full-resolution

### 7.2 Compression

- **Draco:** Mesh geometry compression (10:1 typical)
- **KTX2/Basis:** Texture compression (GPU-native)
- **glTF-Transform:** Optimization pipeline

### 7.3 Performance Targets

- Initial load: <3 seconds on 4G
- Interactive framerate: 60fps desktop, 30fps mobile
- Total download: <50MB for typical artifact

---

## 8. Security & Integrity

### 8.1 Access Control

- Role-based permissions (public, researcher, admin)
- Watermarking for high-res downloads
- Rate limiting to prevent abuse
- Audit logging of access

### 8.2 Data Integrity

- Cryptographic signatures for authenticity
- Blockchain anchoring for provenance (optional)
- Redundant storage (3-2-1 rule)
- Geographic distribution of copies

---

## Appendix: Software Recommendations

### Capture
- Photogrammetry: Metashape, RealityCapture, Meshroom
- LiDAR Processing: CloudCompare, PDAL, LAStools

### Processing
- Mesh editing: Blender, MeshLab, ZBrush
- UV unwrapping: RizomUV, Blender
- Texture baking: Substance Painter, Blender

### Optimization
- glTF: Blender, glTF-Transform
- Compression: Draco, Meshoptimizer, KTX-Software

### Web Delivery
- Viewers: Three.js, Babylon.js, model-viewer
- Platforms: Sketchfab, Smithsonian Voyager

---

© 2025 WIA - World Certification Industry Association
**License:** MIT


## Annex E — Implementation Notes for PHASE-3-PROTOCOL

The following implementation notes document field experience from pilot
deployments and are non-normative. They are republished here so that early
adopters can read them in context with the rest of PHASE-3-PROTOCOL.

- **Operational scope** — implementations SHOULD declare their operational
  scope (single-tenant, multi-tenant, federated) in the OpenAPI document so
  that downstream auditors can score the deployment against the correct
  conformance tier in Annex A.
- **Schema evolution** — additive changes (new optional fields, new error
  codes) are non-breaking; renaming or removing fields, even in error
  payloads, MUST trigger a minor version bump.
- **Audit retention** — a 7-year retention window is sufficient to satisfy
  ISO/IEC 17065:2012 audit expectations in most jurisdictions; some
  regulators require longer retention, in which case the deployment policy
  MUST extend the retention window rather than relying on this PHASE's
  defaults.
- **Time synchronization** — sub-second deadlines depend on synchronized
  clocks. NTPv4 with stratum-2 servers is sufficient for most deadlines
  expressed in this PHASE; PTP is recommended for sites that require
  deterministic interlocks.
- **Error budget reporting** — implementations SHOULD publish a monthly
  error-budget summary (latency p95, error rate, violation hours) in the
  format defined by the WIA reporting profile to facilitate cross-vendor
  comparison without exposing tenant-specific data.

These notes are not requirements; they are a reference for field teams
mapping their existing operations onto WIA conformance.

## Annex F — Adoption Roadmap

The adoption roadmap for this PHASE document is non-normative and is intended to set expectations for early implementers about the relative stability of each section.

- **Stable** (sections marked normative with `MUST` / `MUST NOT`) — semantic versioning applies; breaking changes require a major version bump and at minimum 90 days of overlap with the prior major version on all WIA-published reference implementations.
- **Provisional** (sections in this Annex and Annex D) — items are tracked openly and may be promoted to normative status without a major version bump if community feedback supports promotion.
- **Reference** (test vectors, simulator behaviour, the reference TypeScript SDK) — versioned independently of this document so that mistakes in reference material can be corrected without amending the published PHASE document.

Implementers SHOULD subscribe to the WIA Standards GitHub release notifications to track promotions between these tiers. Comments on the roadmap are accepted via the GitHub issues tracker on the WIA-Official organization.

The roadmap is reviewed at every minor version of this PHASE document, and the review outcomes are recorded in the version-history table at the start of the document.

## Annex G — Test Vectors and Conformance Evidence

This annex describes how implementations capture and publish conformance
evidence for PHASE-3-PROTOCOL. The procedure is non-normative; it standardizes the
shape of evidence so that auditors and downstream integrators can compare
implementations without re-running the full test matrix.

- **Test vectors** — every normative requirement in this PHASE has at least
  one positive vector and one negative vector under
  `tests/phase-vectors/phase-3-protocol/`. Implementations claiming
  conformance MUST run all vectors in CI and publish the resulting
  pass/fail matrix in their compliance package.
- **Evidence package** — the compliance package is a tarball containing
  the SBOM (CycloneDX 1.5 or SPDX 2.3), the OpenAPI document, the test
  vector matrix, and a signed manifest. Signatures use Sigstore (DSSE
  envelope, Rekor transparency log entry) so that downstream consumers
  can verify provenance without trusting a private CA.
- **Quarterly recheck** — implementations re-publish the evidence package
  every quarter even if no source change occurred, so that consumers can
  detect environmental drift (compiler updates, dependency updates, OS
  updates) without polling vendor changelogs.
- **Cross-vendor crosswalk** — the WIA Standards working group maintains a
  crosswalk that maps each vector to the equivalent assertion in adjacent
  industry programs (where one exists), so an implementer that already
  certifies under one program can show conformance to PHASE-3-PROTOCOL with
  reduced incremental effort.
- **Negative-result reporting** — vendors MUST report negative results
  with the same fidelity as positive ones. A test that is skipped without
  recorded justification is treated by auditors as a failure.

These conventions are intended to make conformance evidence portable and
machine-readable so that adoption of PHASE-3-PROTOCOL does not require bespoke
auditor tooling.

## Annex H — Versioning and Deprecation Policy

This annex codifies the versioning and deprecation policy for PHASE-3-PROTOCOL.
It is non-normative; the rules below describe the policy that the WIA
Standards working group commits to when amending this PHASE document.

- **Semantic versioning** — major / minor / patch components follow
  Semantic Versioning 2.0.0 (https://semver.org/spec/v2.0.0.html).
  Major bump indicates a backwards-incompatible change to a normative
  requirement; minor bump indicates new normative requirements that do
  not break existing implementations; patch bump indicates editorial
  changes only (clarifications, typo fixes, formatting).
- **Deprecation window** — when a normative requirement is removed or
  altered in a backwards-incompatible way, the prior major version is
  maintained in parallel for at least 180 days. During the parallel
  window, both major versions are marked Stable in the WIA Standards
  registry and either may be cited as "WIA-conformant".
- **Sunset notification** — deprecated major versions enter a 12-month
  sunset window during which the WIA registry marks the version as
  Deprecated. The deprecation entry includes a migration note pointing
  to the replacement requirement(s) and an explanation of why the
  change was made.
- **Editorial errata** — patch-level errata are issued without a
  deprecation window because they do not change normative behaviour.
  Errata are tracked in a public errata register and each entry is
  signed by the WIA Standards working group chair.
- **Implementation changelog mapping** — implementations SHOULD publish
  a changelog mapping each PHASE version they support to the specific
  build, container digest, or SDK version that satisfies the version.
  This allows downstream auditors to verify version conformance without
  re-running the entire test matrix on every release.

The policy is reviewed at the same cadence as the PHASE document and
any changes to the policy itself are tracked in the version-history
table at the start of the document.