Version 1.4 Release
Version 1.4 of the Backseat Geologist app is now available on the App Store. This version includes a new map tile and geologic data download feature. It also includes UI updates for the new Liquid Glass design language of iOS 26.
New Features
Map Tile and Geologic Data Downloads
It wasn’t on the roadmap, but I realized the importance of being able to download map tiles and geologic data so you can see the geologic map and descriptions of geological formations while offline. This is especially important for areas with poor cell service or to save on data usage during long trips.
I had some challenges getting this off the ground. There is a bit of magic in how MapKit fetches and renders map tiles that I had to decipher. MapKit builds the url string for the map tiles that it needs based on the latitude, longitude, zoom level. Macrostrat’s tile server can return png map tiles or MVT (Mapbox Vector Tiles) data. Depending on the location and zoom level, various data is or isn’t available. My experimentation revealed that MVT data is available only at zoom level 14, one of the highest zoom levels. Once I had the MVT data, I had to parse it and store it in a new core data entity that I could later query based on map taps. MVTTools and GEOSwift were invaluable libraries in this process.
I decided on three zoom levels for png tiles: 8, 10, and 14. The tiles are saved in their own core data entities so they can be queried later. Since there are gaps in the zoom levels I included some upscaling to fill in the gaps. The existing tile manager was updated to check for offline data if the server is not reachable.
The result is that when you are on certain zoom levels a download button will appear on the right side of the screen. Tapping the button will open the download sheet and display the estimated storage requirement, number of tiles, and estimated download time. You can then tap the download button to start the download. Once the download is complete, the tiles will be available for offline use. Browsing and tapping the map when offline will work pretty much the same as if you are online with geologic info panel data and colorful geologic map tiles in the downloaded area.
This feature is only available to subscribers.
Liquid Glass
This update also includes the new Liquid Glass design language of iOS 26. Liquid Glass adds a new transparency and refraction effect to UI elements. It adds some flair to the app without effect readability too much. Screenshots are updated on the home page to show the new design language.