Files
karten/docs/adr/0001-offline-pwa-prepared-tiles.md
konradandCursor 3a49d52681 Record that downloads fill the Cache and ship the built app.
A failed open can repair the shell, and the installed PWA matches Ziele, Einstellungen, and the view download.

Co-authored-by: Cursor <cursoragent@cursor.com>
2026-10-09 08:55:43 +02:00

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Markdown

---
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 fetches it into the Cache, 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. Fetching Hessen, or fetching the Kacheln that intersect the current view, covers every one of those scales, the Kacheln of the current scale first. Fetches run only while that app is open and the device is online. Leaving the app stops them, and opening it again does not continue them. While the app stays open, losing the network pauses a fetch and regaining it continues that fetch. Looking around fetches only the current view at the current scale. Kacheln leave the device only when the whole Cache is deleted. Why a download does not mark a Gebiet is [ADR 0003](0003-downloads-fill-the-cache.md).
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.