# Credits — ISS atlas model

## Geometry

`public/model/iss.glb` and `iss_lod1.glb` are derived from **International Space Station (D) (IGOAL)**,
`nasa_iss_D_IGOAL.glb`, by **NASA / Johnson Space Center / Integrated Graphics, Operations and Analysis
Laboratory (IGOAL)**, published through [NASA 3D Resources](https://science.nasa.gov/3d-resources/)
([GitHub mirror](https://github.com/nasa/NASA-3D-Resources)).

The source is a **U.S. Government work in the public domain**. No attribution is legally required;
NASA is credited here as good practice. The
[NASA Images and Media Usage Guidelines](https://www.nasa.gov/nasa-brand-center/images-and-media/)
apply: **nothing here implies NASA endorsement of this atlas**, and the NASA insignia is not used.

## What was changed

| Change | Detail |
|---|---|
| Coordinate frame | The source root carried a uniform **negative** scale, i.e. a point inversion that renders the model mirrored. It was replaced with a proper rotation (180° about X) plus a positive uniform scale of **0.02623036 m per source unit**, so the exported model is right-handed and **not** mirrored. Source frame measured (not assumed) from known berthing ports: +X forward, +Y nadir, +Z port. |
| Scale and origin | Fitted by least squares against 32 landmarks from `01_station/ISS_master_dimensions.md` §4, with outlier rejection. Residuals are in `build_report.json.landmarks`. |
| Node names | 95 nodes renamed to the atlas's canonical slugs via `13_reference_models/igoal_node_map.json`. 492 nodes keep an `igoal_*` identifier and are flagged `unmapped`. |
| Metadata | Every node carries `extras` per `00_MASTER_BRIEF.md` §6, populated from `12_interaction/component_tree.json`. |
| Decimation | 2,707,621 → 1,291,397 triangles (LOD0) → 376,289 (LOD1), meshopt per primitive with a floor so no node disappears. |
| Textures | Re-encoded to WebP, capped at 2048 px (LOD0) and 1024 px (LOD1). Lossy. |
| Compression | KHR_draco_mesh_compression on both outputs. |

## What this is not

This is an **educational reconstruction, not a certified CAD model**. The IGOAL source ships without a
dimension sheet, and every coordinate in `01_station/ISS_master_dimensions.md` is itself `*derived*`
from datum M′ — no public NASA CAD or ICD was reachable. Where the two disagree the disagreement is
recorded in `build_report.json`, not silently resolved. After the fitted transform the truss span
measures **102.55 m** against the package's 108.5 m headline figure, and the solar array span
measures **75.82 m** against 72.8 m. One uniform scale cannot satisfy both, so the model's
proportions differ from the sourced dimensions.

The `cutaway_config.json` "skin" lists are a **name-based heuristic**, not an engineering breakdown of
what is structure and what is a shield panel. The model has no interior geometry.

Everything estimated is enumerated in `build_report.json.caveats`.

## Package text and data

Text, component tree, timeline and dimension tables in this repository are original work written from
the sources in `11_sources/Sources_and_bibliography.md`. Imagery is credited separately in
`10_images/ATTRIBUTION.md` — **ESA and JAXA imagery is not public domain.**