Background imagery

Three built-in tile sources:

• ESRI Imagery (Satellite) — global high-res aerial imagery, current-ish.
• USGS NAIP (US Imagery) — North American agricultural imagery, sometimes more recent for fields than ESRI.
• None — no online tile background. Map renders against the surface color (works well when KML / image overlays carry the geographic context).

Tap the Layers FAB → Background to switch. Your choice persists.

Offline tiles: the app caches tiles with the flutter_map_tile_caching package. Once a region is panned over while online, it is available offline. LiDAR & Mapping also has a deliberate Cache Satellite Imagery / Prepare Field flow: draw a rough boundary while online and the app caches the appropriate imagery and reference-label tiles for that field. When All Files Access is granted, the map tile cache is stored under Documents/DitchAssist/map-tile-cache so it can survive reinstall; otherwise Android may keep it in private app storage and it can be removed with the app.