# London · US Arrivals Atlas — technology and research notes

Research checked 18 September 2026. Arrival window: 18 September 2021–18 September 2026. Announced arrivals, re-entries, temporary activations and qualified US-origin cases are identified rather than mixed into confirmed permanent openings.

## GitHub review and implementation

- **GeoLibre** — https://github.com/opengeos/GeoLibre (MIT). Inspected the repository, project schema, Python `project.py` builders, popup types and embedding/filtering interfaces. The included `.geolibre` is generated through its official Python project API with eight styled layers, evidence attributes, Quick Filters, chart widgets and a print layout. It is a real portable GeoLibre project, not a renamed CSV. Open it with GeoLibre's Project → Open command. All mapped data is embedded; basemap tiles require internet.
- **MapLibre GL JS** — https://github.com/maplibre/maplibre-gl-js (BSD-3-Clause). Used directly for the tailored browser interface: vector basemap, individual point picking, fly-to navigation, heatmap layers and 3D extrusion. The BSD license is retained in `vendor/LICENSE-maplibre.txt`. Library assets are included locally rather than depending on an unpinned CDN.
- **Supercluster** — https://github.com/mapbox/supercluster (ISC). Reviewed its point-count clustering approach. This dataset is small enough for individual WebGL points, so the interface avoids arbitrary zoom-driven cluster totals and offers deliberate spatial aggregation instead. The filtered GeoJSON source is rebuilt on every filter change.
- **deck.gl** — https://github.com/visgl/deck.gl (MIT). Reviewed its GPU layer architecture. A second rendering engine was unnecessary for this data volume: MapLibre's native heatmap and fill-extrusion layers deliver the required interaction with a smaller application.
- **H3** — https://github.com/uber/h3 (Apache-2.0). Reviewed hierarchical hex indexing. The atlas uses a transparent fixed London-centred local hex grid instead, so its 500m display cells retain consistent geometry under filtering. It is not an H3 index. Grid width is approximately 500m between opposite sides; this is an analytical display, not a cadastral measurement.
- **OpenFreeMap** — https://openfreemap.org/quick_start/ and https://github.com/hyperknot/openfreemap. Provides the attributed OSM-based vector basemap. Map data © OpenStreetMap contributors. Basemap availability and tiles depend on this external service.
- **Postcodes.io** — https://postcodes.io/docs/ and https://github.com/ideal-postcodes/postcodes.io. Verified UK postcodes are converted to postcode-centroid coordinates when operator coordinates were unavailable. These positions should not be interpreted as surveyed shopfronts.

### Filtering and aggregation

Brand, category, trading status, premises format, text search and arrival cohort filters operate on the underlying location records. Point layers, heatmaps and density hexagons use exactly the same filtered record set. Each mapped record contributes once to its hexagon, including co-located concessions. Hex height equals 48 display metres per record; the height is a visual encoding, not a real building height.

The slider uses the **directory entry milestone year** and shows the brand's researched present footprint. This may represent a first standalone store after earlier concessions. The Frankie Shop's current Selfridges space is therefore under the planned 2027 standalone cohort; All years retains it. It does not reconstruct historical store counts. Planned and unresolved opening dates remain explicitly distinguished. GeoLibre's own time-slider filters do not necessarily recompute clustered counts; the delivered GeoLibre project uses individual points and Quick Filters, avoiding that mismatch.

The 500m nearby view uses a straight-line haversine distance from the selected coordinate. It is not a walking isochrone. Postcode-level uncertainty matters around the edge of this radius.

## How the research was assembled

The original 70 operator entries were expanded into premises using current operator directories, location pages, landlord pages and opening/closure evidence. Rothy's Liberty concession was added after verification, giving 71 brand/operator records. This is the reviewed cohort, not an exhaustive census of every US-origin retail brand ever active in London.

Blank Street's embedded official location JSON provided 40 addresses and coordinates, with Marble Arch temporarily closed. Popeyes' public locator provided 34 trading Greater London restaurants plus planned Putney; delivery kitchens were excluded. Other addresses were checked against operator/landlord evidence and individually geocoded. Sources are carried per record and in the coverage register.

- **Open:** sources indicate a currently operating location.
- **Temporary:** currently operating, explicitly temporary or a residency.
- **Planned:** announced premises, not verified as trading.
- **Temporarily closed:** retained physical site explicitly paused.
- **Closed:** documented historical location / ended temporary activation.
- **Unverified:** historical or announced premises whose current operation cannot be confirmed.

`complete operator list` means the reviewed operator's published current list was reconciled to the stated scope; it is not a guarantee against a very recent unannounced change. `partial` indicates incomplete estate or uncertain store-format coverage. `no current sites verified` does not mean no historical presence.

## Coordinate precision and Greater London

75 original records use operator-supplied points. Most other records use postcode centroids. Shopping centre concessions may share a single coarse centroid. Addresses without a verified spatial reference remain unlocated rather than receiving neighbourhood guesses. Null geometries are retained in the complete GeoJSON/CSV; the styled GeoLibre map embeds only located points. The source coordinate URL and precision label travel with each record.

Greater London is the working geography; Bluewater, Lakeside and Watford are excluded. Co-located stores, licensed concessions, brand residencies and hotel restaurants are brand-premises records, not independent leases. The database does not contain lease terms, rent, footfall, sales or evidence of unsatisfied demand.

## Files

- `london-us-arrivals.geolibre`: native GeoLibre project; embedded layers, popup fields, Quick Filters and chart widgets.
- `london-us-arrivals.geojson`: full WGS84 location feature collection; null geometry for unlocated records. Open in QGIS with Layer → Add Layer → Add Vector Layer.
- `london-us-arrivals.csv`: full attribute register, including unlocated premises.
- `coverage.json`: per-brand coverage scope, expected count when supported, and evidence URLs.
- `atlas-data.json`: complete structured source used by the browser, including brand context.
- `README.md`: concise usage and methodology.

Research is a dated snapshot. The app does not automatically monitor openings or closures.