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karten/docs/adr/0001-offline-pwa-prepared-tiles.md
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2026-10-09 04:20:40 +02:00

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status
accepted

Offline PWA with prepared raster tiles

The Karte is an installable app for phone and tablet, with no app store and no live map server. The Mac turns the DTK25 Blätter into Kacheln once. A Kachel reaches the device because the user downloads a Gebiet, or because the open Karte needs it and the device is online. The open Karte reads only the Kacheln inside the current view. The furthest zoom-out is a ground span shipped in the app configuration, 36 km by 36 km unless that file is changed. The prepared Kacheln cover every scale from that span down to the native sheet pixel. Downloading a Gebiet fetches all of those scales, the current view first. Downloads run only while that app is open and the device is online; leaving the app pauses them, and opening it again continues them. Which of those Kacheln a delete keeps is ADR 0002.

A macOS desktop app was rejected. Serving the original GeoTIFFs from the Mac while the phone is on the same network was rejected, because the Karte has to work after the download, with that computer left behind.