In this repository I prototype a vector map tile rendered. I am using an extract from the OSM maps provided by OpenMapTiles. I am using the freely available snapshot of Prague from 2017-07-03.
https://openmaptiles.com/downloads/dataset/osm/europe/czech-republic/prague
MBTILES file format is a SQLite database with a specific schema, documented here:
https://github.com/mapbox/mbtiles-spec
I am working on a JavaScript SQLite database library found here:
https://github.com/TomasHubelbauer/sqlite-javascript
Unfortunately it is not possible to use WebSQL to access the database, because it is barely supported (works in Chrome and Safari though) and is not able to work off a given file.
The vector tiles are stored in the ProtoBuf format in the database table called
images. This is true of the particular database included in this repository,
but the MBTILES format also supports raster tiles. To check what sort of tiles
your MBTILES database contains, check the metadata table, the format column
in particular.
The vector tile database file is loaded upon user gesture and with loading indicator, because it is really big (70 MB).
I am toying around with an idea of using a service worker to cache the file when
the user clicks the download button and the application determining whether it
was already downloaded or not by inspecting the caches object or issuing a
request with some marker (header/fragment/query) which would tell the worker to
actually download if present or fail to indicate not having been cached yet if
not present.
The worker might break the download indication (worried it will split the pipeline into two steps - worker downloads and then the page downloads from the cache) so if that's the case, we can try ranged fetch to preserve the ability to download with indication as GitHub Pages support ranged requests.
Because the MapBox one sucks and there don't seem to be others not requiring the schema
- https://www.qwant.com/maps/tiles/ozpoi/14/8853/5549.pbf
- Consider merging this with my osm-bitmap-map and allow both bitmap and vector servers!
- https://betterweb.qwant.com/qwant-maps-a-open-and-privacy-focused-map
- https://www.qwant.com/maps
- https://mapserver.mapy.cz/bing/11-1116-708 this is alternative rasters below? This one is used by the app