# Method — how this derivative database was made

This document and the scripts listed in `manifest.json` are offered under the
Open Database License together with the dataset itself
(`/artifacts/airside/atl-osm-w3.geojson`), as ODbL 1.0 section 4.6 requires:
either the entire Derivative Database, or a file containing all the
alterations made to the Database — or the method of making those alterations.

## What this database is

A Derivative Database of OpenStreetMap data: a clipped, normalised subset of
the Geofabrik Georgia extract (`georgia-latest-2026-09-27T20:23:36Z`), shaped
for an airport-area orientation view. It is offered under ODbL 1.0.

- Source: OpenStreetMap contributors, via the Geofabrik Georgia extract.
- Source licence: ODbL 1.0 — <https://opendatacommons.org/licenses/odbl/1.0/>
- Attribution (required on every use): "© OpenStreetMap contributors, ODbL 1.0;
  extract delivered by Geofabrik" — <https://www.openstreetmap.org/copyright>
- Feature count: 2,671 · SHA-256: recorded in `manifest.json`.

## The alterations we made

1. **Extraction** (`extract-atl-osm-w3.mjs`): the source extract is read and
   the airport-area features are selected.
2. **Clipping** (`clip-atl-osm-w3.mjs`): the features are clipped to the
   airport-area boundary and written as GeoJSON.
3. **Normalisation and derivation** (`extract-atl-osm-clipped-w3.mjs`): the
   clipped features are re-shaped into a flat feature collection with a
   normalised property vocabulary. Derived values include `concourse` and
   `level`, computed by polygon containment against the source extract, and
   parsed opening hours. **These derived values are our computation, not
   operator-confirmed.**
4. **Promotion and reconciliation** (`promote-staged-osm-local.mjs`): the
   feature set is reconciled against the source revision and recorded in a
   promotion manifest (feature count, conflicts, unknown fields, authority
   claim, rollback).

Each feature carries its own `attribution` field.

## What we deliberately did not do

- We did **not** merge any airport-operator, licensed-provider or other
  non-ODbL records into this database. ODbL 4.4(d) prohibits adding contents
  that are incompatible with the licence's grants, and doing so would extend
  share-alike to data we do not hold rights to. Where such layers are
  needed, they are kept as separate databases and joined only at display
  time (ODbL 4.5(a), Collective Databases).
- We did **not** repackage route or walking geometry into a reusable dataset.
  Route results are produced per request and carry the map's attribution
  (OSMF Attribution Guideline 1.5.5).
- We did **not** assert operator authority. No written decision has been
  obtained from the City of Atlanta Department of Aviation or a licensed
  indoor/wayfinding provider, so this dataset carries no terminal, gate,
  accessibility, security, airside-access, hours or closure-status truth, and
  it must never be presented as official airport guidance.

## Reusing this data

If you use this database publicly, you must:

- credit OpenStreetMap and the ODbL, visibly, on the map itself;
- publish your own derivative database under ODbL 1.0, and offer the whole
  derivative database (or the alterations) to your users over the internet, free
  of charge, in machine-readable form;
- keep the licence terms unaltered, and keep OSM-derived data in its own
  layer.

These obligations are the same ones we accepted for this publication.