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lightcraft/crates/geocode/README.md

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lightcraft-geocode (L1)

Offline reverse geocoding: a GPS position becomes Sublocation / City / State / Country.

  • Data: the GeoNames dump (https://download.geonames.org/export/dump/), licensed CC-BY 4.0 (attribution: "GeoNames, geonames.org"). Nothing is bundled: the engine (metadata.downloadPlaceNames) downloads cities15000.zip, admin1CodesASCII.txt and countryInfo.txt on the user's request into the settings folder. This crate only parses and searches; it never touches the network.
  • Lookup: the nearest populated place within MAX_KM (great-circle distance), searched in the 1° cells around the position, so one lookup looks at a few dozen places, not all of them.
  • unzip: just enough ZIP to read one file out of cities15000.zip (stored or deflated).
  • Never panics on hostile input: bad lines are skipped, NaN / out-of-range positions find nothing, sizes and counts are capped.

Sources: GeoNames dump readme (file layout, prose); haversine distance (textbook); PKWARE APPNOTE (ZIP, prose spec); the cell index is own design.