Preparing offline maps

This page may require some technical knowledge about geospatial data. If the content of this page feels unfamiliar to you, get someone acquainted with geographic information systems (GIS) to help you.
For offline or mesh network usage, Terrastories can load a background map using an open-source map tileserver called TileServer-GL and locally hosted map tiles, instead of a map from Mapbox. This requires you to provide your own locally hosted map tiles.
Terrastories does provide a default set of open-license offline map tiles, generated through the OpenMapTiles API. These tiles cover the entire world, but are only compiled up to zoom level 8 (roughly the extent of a small country like Rwanda, Costa Rica, Slovenia or Bhutan). Once you zoom in past zoom level 8, no further level of detail will show.
When you set up Terrastories for 🛖 Hosting Terrastories offline as a "Field Kit" or 🖧 Hosting Terrastories on a mesh network, you will be given the option to use these default offline map tiles. However, you can also provide your own map tiles, which have to be in a mbtiles format, and provided alongside any map fonts, sprites, and a style.json file where the mbtiles file is placed on a map canvas.
Our setup script, which detects if you already have a style.json file in your tileserver/data directory, and if not, downloads the default offline tiles for you.

How to generate or convert MBTiles

MBTiles can be generated from standard geospatial data (Shapefile, GeoJSON) in several ways.
  • The open-source GIS software QGIS has several tools for generating MBTiles in both raster and vector format. Generate XYZ tiles (MBTiles) can be used to create raster tiles of all of the content on your map canvas; this may also include XYZ Tiles from services such as OpenStreetMap, Bing, and Google Satellite. Generate Vector Tiles (MBTiles) can be used to create vector tiles from one or more vector layers. You can then further style these vector tiles in your style.json file.
  • There is also a command line tool called tippecanoe which can be used to generate vector MBTiles from Esri Shapefiles and other formats: guide.
  • If you already have tiles in a different format (such as xyz), you can use a Node command line tool called mbutil to convert them to MBTiles. Please see our xyz to mbtiles conversion repository or this page Generating map files in .mbtiles format for the experimental Background Maps feature in the Mapeo support materials for more information.
Once generated, place the MBTiles in the tileserver/data/mbtiles/ directory, with the right filename as referenced by style.json.
Working with custom styles
Map styles (per the style.json schema) defines the visual appearance of a map: what data to draw on the map canvas, the order in which layers are displayed, and how to style the data when drawing it. Mapbox provides a helpful guide with all of the possible style parameters, but it's generally useful to download an existing style.json file and modify it to suit your needs. One of the easiest ways to build a style.json file is by uploading and styling your data on Mapbox Studio and downloading the style.json file from there, in the following way:
  • Follow the map design process described here.
  • In the Mapbox Studio environment, click "Share" and then download the Map style ZIP file.
  • Unzip the file, and extract the style.json and place it in tileserver/data/styles.
  • Next, you will need to make some changes. The style.json from Mapbox will be referring to an online URL for the map sources. You need to change this to refer to the local MBTiles. Change sources > composite > url to the following format: "url": "MBTiles://MBTiles/name.MBTiles". (Here, name is just an example; it can be called whatever you want, so long as the filename is the same.)
Importantly, the layer names referenced in styles and MBTiles have to match, in order for the tiles to receive a style property. It may be necessary to edit the layer names in style.json to reflect the names of the spatial data in the MBTiles file.
Raster tiles: If you have raster tiles that you want to load in Terrastories, those will need to defined differently from the vector tiles above. In sources, create a new source definition with url pointing to the raster MBTIles in the same format as above, type set to raster, and tileSize to 256. Then, in layers, create a map object with your id of choice, type set to raster, and source set to the name of your raster tiles as defined in sources. Here is an example:
"sources": {
"raster-tiles": {
"url": "mbtiles://mbtiles/raster.mbtiles",
"type": "raster"
"tileSize": 256
}
},
"layers": [
{
"id": "raster-background",
"type": "raster",
"source": "raster-tiles"
},
You can define multiple mbtiles sources (vector as well as raster), and place your raster tile layer underneath vector layers. This is a good way to have an offline satellite imagery basemap with vector data (points, lines, polygons, and labels) overlaid on top of it.
​