GeoPackage Tiles (OGC raster tiles in SQLite)

GeoPackage Tiles is the official extension of the OGC GeoPackage standard: raster map tiles sit as PNG blobs inside an ordinary SQLite file, while service tables describe the zoom pyramid and the georeferencing. One file, no companion folders, no tile server.

This export is taken for work without the internet: a tablet in the field, a site visit, an expedition where the signal drops out. You put the file into the device's storage, the application opens it as an ordinary basemap — and the map of the area stays at hand regardless of the network.

The file holds the selected area rendered into 256x256 pixel tiles in the Web Mercator projection (EPSG:3857) following the GoogleMapsCompatible scheme, together with the gpkg_contents, gpkg_tile_matrix_set and gpkg_tile_matrix service tables. By default the zoom range runs from ten to sixteen — from a city overview down to individual buildings; the bounds of the range are set at export time.

The tiles are raster: this is a picture, not features — OSM tags are not preserved in them and clicking a building returns nothing. The tile count grows fourfold with every zoom level, so there is a limit of 50,000 tiles per file: with too large an area and deep zoom the export will stop, and the range has to be narrowed.