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# Initial plan

## Inputs

| Source | What |
|---|---|
| Geofabrik | `japan-latest.osm.pbf`, 2.3 GB, or a regional extract |
| Protomaps daily planet | sliced by bounding box, no planet download needed |

Start with the region actually driven rather than all of Japan. Geofabrik publishes
Kantō, Chūbu, Hokkaidō and others separately.

## Steps

1. Fetch the PBF for the target region.
2. `valhalla_build_admins` — driving side and border data.
3. `valhalla_build_tiles` — the routing graph, output as a directory.
4. `go-pmtiles extract` against the Protomaps planet for the same bounding box.
5. Record source dates and output sizes in a report under `docs/impl/reports/`.

## Delivery

Out of scope for now — the artifacts are moved by hand. When it stops being
tolerable, `rsync` over the LAN only, never over LTE, with `--partial-dir` so a
transfer survives being cut off. Swap atomically: build beside the live copy,
symlink-swap, restart. Never overwrite tiles the server is reading.