Using offline (local) tiles with GNOME Maps

I managed to get a freeze exception to include a new feature in Maps for 3.18. It is now possible to use local, offline, tiles by using the --local command line option.
What you need are image map tiles, organized in a standard way in a directory. Then you can point Maps towards that directory and have local tiles usable offline.

For instance, I downloaded a bounding box of London. In the zoom-levels of 11, 12, 13, 14 and 15. The tiles are organized as Z/X/Y.png. Where Z is zoom-level, X and Y are the tile numbers. London at those zoom-levels will be 2750 tiles and about 60M.

I used a perl script found while googling. Please be advised to follow the tile servers usage policy before attempting bulk downloading of tiles.

$ tree london/
london/
├── 11
│   ├── 1022
│   │   ├── 679.png
│   │   ├── 680.png
│   │   ├── 681.png
│   │   └── 682.png
│   ├── 1023
│   │   ├── 679.png
│   │   ├── 680.png
│   │   ├── 681.png
│   │   └── 682.png
│   └── 1024
│       ├── 679.png
│       ├── 680.png
│       ├── 681.png
│       └── 682.png
├── 12
│   ├── 2044
│   │   ├── 1359.png
│   │   ├── 1360.png

Using this I can do:

$ jhbuild run gnome-maps --local ~/london

So this is kind of an hidden feature. So that we can test using offline tiles before we find a way of getting downloading into Maps. One kind of major issue right now is where do we get the tiles? Bulk downloading tiles from OpenStreetMaps is not very nice. OSM is a non-profit org. run by volunteers on donations. We do not want to leach on bandwidth. So we need a way around this. Maybe host our own?

Please also consider that when and if you want to download tiles to try this Maps feature. See the tile usage policy about bulk downloading. And try to follow it!

Please enjoy!