Generating Raster Tiles from Vector Map Data

A collection of tools--with (hopefully) clear documentation--for generating raster map tiles from vector map data and a Mapbox GL style.

The toolchain consists of Maputnik for creating/editing Mapbox GL styles, Tileserver GL to apply the style(s) to vector map data and serve up raster tiles, and a custom script to scrape and save the tiles as PNGs.

How to Generate Tiles

Here's everything you'll need to do to generate tiles. Some stuff I've already done for you and included in this project. I'll walk you through the rest.

Tileserver GL

First, you'll need Tileserver GL installed. There are at least a couple ways to install, but apparently using Docker is the easiest. Go ahead and skip to that section below unless you want details on what doesn't work.

Installing with Node.js

The tl;dr is that you shouldn't even bother trying to just do the simple npm install -g tileserver-gl method. You'll go crazy. If you use Node.js 8.x, it'll fail due to a 403 when pulling one of the assets. Turns out you need to have Node 6.x (see maptiler/tileserver-gl#216). I switched to Node.js 6.12.1 and retried and, hey, guess what?!? That failed too with this lovely error:

ENOENT: no such file or directory, rename '/Users/chris/n/lib/node_modules/.staging/@mapbox/point-geometry-c12f351f' -> '/Users/chris/n/lib/node_modules/tileserver-gl/node_modules/@mapbox/point-geometry'

Googling that and you'll find a bunch of posts which pretty much just say, "screw it, man, just use docker". So, using Docker...

Installing with Docker

Despite complaints from coworkers about how annoying Docker is, it seems to be my best (only?) option for the Mac, so I installed Docker, ran it, and logged in.

Following the instructions at https://openmaptiles.org/docs/host/tileserver-gl/, I tried installing tileserver-gl by doing this:

docker pull klokantech/tileserver-gl

Since nothing can ever just be easy, that failed with this error:

$ docker pull klokantech/tileserver-gl
Using default tag: latest
Error response from daemon: Get https://registry-1.docker.io/v2/klokantech/tileserver-gl/manifests/latest: unauthorized: incorrect username or password

Hmmm, so even though I was logged in to Docker in the menu item thing, maybe I need to log in on the command line too? So I tried this:

$ docker login
Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub.docker.com to create one.
Username (bartley@cmu.edu): 
Password: 
Error response from daemon: Get https://registry-1.docker.io/v2/: unauthorized: incorrect username or password

OK, now that's just weird. I tried again, this time with my username instead of my email address:

$ docker login
Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub.docker.com to create one.
Username (bartley@cmu.edu): chrisbartley
Password: 
Login Succeeded

I'm beginning to understand why my coworkers complain abut Docker [sigh]. Anyway, after that, the installation of tileserver-gl worked fine:

$ docker pull klokantech/tileserver-gl
Using default tag: latest
latest: Pulling from klokantech/tileserver-gl
3e731ddb7fc9: Pull complete 
47cafa6a79d0: Pull complete 
79fcf5a213c7: Pull complete 
68e99216b7ad: Pull complete 
4822563608bb: Pull complete 
bd223a5eb9f8: Pull complete 
af1ecaa3fb91: Pull complete 
ab24011f6a41: Pull complete 
0f94701268e1: Pull complete 
e7c634c94e3f: Pull complete 
b1c059f00dd4: Pull complete 
09313f85da09: Pull complete 
b63ade49cecb: Pull complete 
5d6c8934e668: Pull complete 
Digest: sha256:12b907724940051ffb2ca7dfe82c7da9e4e51e84556f5514173858e407e8f81c
Status: Downloaded newer image for klokantech/tileserver-gl:latest

Other Required Pieces

Before trying to run it, you'll need to download some required bits, just because they're too big to put in this project.

Map Data

You'll need vector map data. If you want the whole planet, you'd better have both time and disk space...it's ~51 GB. I did my initial tests with two different datasets: the United States and Great Britain. They're large, 6.7GB and 1.2GB respectively, so they're not included here. You'll need to download the .mbtiles archives from OpenMapTiles here:

      Whole Planet
      https://openmaptiles.com/downloads/planet/

      United States
      https://openmaptiles.com/downloads/north-america/us/

      Great Britain
      https://openmaptiles.com/downloads/europe/great-britain/

Just save them into the tileserver-gl/mbtiles directory in this project.

Fonts

The styles we're using require some fonts. Note that I'm using v1.1, because v2 changes the name of some fonts, but the styles below haven't been updated accordingly (yet?). Anyway, you can download the zip from here:

      https://github.com/openmaptiles/fonts/releases/tag/v1.1

Extract the zip into a directory named fonts located under the tileserver-gl directory in this project.

Styles

I've already downloaded and included some styles in the project, but here's where I found them.

      Klokantech Basic v1.3
      https://github.com/openmaptiles/klokantech-basic-gl-style/releases

      OSM Bright v1.3
      https://github.com/openmaptiles/osm-bright-gl-style/releases

      Positron v1.4
      https://github.com/openmaptiles/positron-gl-style/releases

      Dark Matter v1.3
      https://github.com/openmaptiles/dark-matter-gl-style/releases

I've also included some styles of my own based on some of the above.

Config

I've included three tileserver-gl configuration files for the styles included here plus the map data and fonts you downloaded above:

tileserver-gl-config-planet.json
tileserver-gl-config-north-america_us.json
tileserver-gl-config-europe_great-britain.json

If the mbtiles files you downloaded have filenames different than what's referenced in the above JSON config files, you'll need to fix the config file(s) accordingly.

Running Tileserver GL

Now that all the pieces are in place, you should be able to run tileserver-gl and explore the map data with each of the various styles. Open a terminal window and cd to the tileserver-gl directory of this project and run one of these commands, depending on which data set you want to view:

docker run --rm -it -v $(pwd):/createlab -p 8080:80 klokantech/tileserver-gl --config /createlab/tileserver-gl-config-planet.json

or

docker run --rm -it -v $(pwd):/createlab -p 8080:80 klokantech/tileserver-gl --config /createlab/tileserver-gl-config-north-america_us.json

or

docker run --rm -it -v $(pwd):/createlab -p 8080:80 klokantech/tileserver-gl --config /createlab/tileserver-gl-config-europe_great-britain.json

Brief description of some of the parts of those commands:

• -v $(pwd):/createlab Mounts a volume in Docker named /createlab and binds it to the current directory. This lets us reference files in the Mac OS filesystem from tileserver-gl. Notice the various paths in the tileserver-gl config files which start with /createlab
• -p 8080:80 Maps port 8080 on the Mac to port 80 in Docker.
• --config /createlab/*.json Tells tileserver-gl where to find the config file

Once it's running, test it out by opening a browser and going to http://localhost:8080/.

Maputnik

Maputnik is a really nice, browser-based editor for Mapbox GL styles. If you're happy with the styles included here, you can skip this entire section and just jump down to the Generating Tiles section below.

Installing Maputnik

The tl;dr is to just use a prebuilt binary. And if you're on a Mac, I've included one in the project. Now for the longer story...

Instructions for installing are here:

      https://github.com/maputnik/editor

What they don't make clear is that installing it fails with both Node.js 4.x and 6.x. I finally got it installed with Node.js 8.9.2. But, they also don't make clear how you can use this version to edit an existing file, other than doing an "upload". The pre-built binary version has an option to specify a JSON style file, and even watch for external changes to that file. That's easier, so just use the latest prebuilt binary, which you'll find here (I'm using maputnik_darwin v1.0.1):

      https://github.com/maputnik/editor/releases

I've included the binary in this project, so if you're on a Mac you shouldn't need to do anything, just run it.

Slight Wrinkle

The only wrinkle is that the style file has URLs for where it can find vector map data, sprites, and fonts ("glyphs"). I have two for Maputnik, and a slightly different one for Tileserver GL. If you compare these files...

tileserver-gl/styles/osm-bright-cpb-gl-style/maputnik-style-local.json
tileserver-gl/styles/osm-bright-cpb-gl-style/maputnik-style-remote.json
tileserver-gl/styles/osm-bright-cpb-gl-style/style-local.json

...you'll see those three fields differ as shown below:

maputnik-style-local.json

  "sources": {
    "openmaptiles": {
      "type": "vector",
      "url": "http://localhost:8080/data/v3.json"
    }
  },
  "sprite": "http://localhost:8080/styles/osm-bright-cpb/sprite",
  "glyphs": "http://localhost:8080/fonts/{fontstack}/{range}.pbf",

maputnik-style-remote.json

  "sources": {
    "openmaptiles": {
      "type": "vector",
      "url": "https://free.tilehosting.com/data/v3.json?key={key}"
    }
  },
  "sprite": "https://openmaptiles.github.io/osm-bright-gl-style/sprite",
  "glyphs": "https://free.tilehosting.com/fonts/{fontstack}/{range}.pbf?key={key}",

style-local.json

  "sources": {
    "openmaptiles": {
      "type": "vector",
      "url": "mbtiles://{v3}"
    }
  },
  "sprite": "{styleJsonFolder}/sprite",
  "glyphs": "{fontstack}/{range}.pbf",

The difference between the two maputnik style files is that maputnik-style-local.json is configured to get all vector data tiles, sprites, and fonts locally, from Tileserver GL. And thus you'll need to have Tileserver GL running for Maputnik to be able to work and edit that style file, and you'll also need the vector map data to be local. The maputnik-style-remote.json file is configured to pull all vector data tiles, sprites, and fonts from the cloud. I prefer the local one since I like the style I'm editing to be using the exact same assets that the tile generation will be using.

Finally, the style-local.json is just for Tileserver GL (and is referenced in the various tileserver-gl-config-*.json files).

The most important thing to remember is that, once you get the style working how you want it--regardless of whether you're using the local or remote maputnik style file--you must apply those changes to the other two style files. And be sure to also fire up Tileserver GL to check your work. I've seen cases where Maputnik and Tileserver GL interpret the style JSON differently.

Bug Fixing

You may notice that the Dark Matter CPB and Klokantech Basic CPB styles have two extra style-local-* files, one for fixing clipped countries, and another for fixing clipped states. I noticed at levels 0-2 that the label for New Zealand would get clipped and appear as "New Zeala". Similarly, the labels for Pennsylvania and Mississippi would get clipped at level 4. These extra style files simply remove the labels for those problem labels altogether. There's probably a more efficient way of doing it, combining it all into a single style file with more rules. I tried that, and it seemed to work in Maputnik, but then didn't work in Tileserver GL, maybe because they interpret the rule cascading differently? Anyway, for my final tileset, it was easy enough to just create separate style files and then generate levels 0-2 with style-local-fixed-clipped-countries.json, levels 3 and 5-12 with style-local.json, and level 4 with style-local-fixed-clipped-states.json.

Update: I've figured out how to merge these clipped name fixes into the same style file as the main one, and have done so for dark-matter-cpb-english-only-gl-style and klokantech-basic-cpb-english-only-gl-style.

Running Maputnik

From this project's root directory, launch Maputnik to edit the OSM Bright CPB style with:

./maputnik/maputnik_darwin --watch --file ./tileserver-gl/styles/osm-bright-cpb-gl-style/maputnik-style-local.json

For the Klokantech Basic CPB style, launch with:

./maputnik/maputnik_darwin --watch --file ./tileserver-gl/styles/klokantech-basic-cpb-gl-style/maputnik-style-local.json

For the Dark Matter CPB style, launch with:

./maputnik/maputnik_darwin --watch --file ./tileserver-gl/styles/dark-matter-cpb-gl-style/maputnik-style-local.json

Then open a browser and go to http://localhost:8000.

If you make changes, don't forget to apply them (but not the three URLs shown above!) to style-local.json.

The Style Editing and Verification Process

Here's what to do to edit a style:

1. Run Maputnik, pointed at the maputnik version of the style you want to edit. The "maputnik version" just means those three URLs are pointing to the cloud rather than local. In this repo, that's the maputnik-style-local.json file.
2. Copy style changes to the tileserver-gl version of the style. In this repo, that's the style-local.json file.
3. Run tileserver-gl, and verify that your style looks good with the vector map data you have.

Generating and Fetching Tiles

At long last, we can finally generate and fetch the tiles...

It's simple enough to just write a script to fetch all tiles for a given level and lat/long bounding box directly from Tileserver GL, so that's what I did. It's a Node.js script in the tile-fetcher directory. I used Node.js 8.9.2, but it might work for other versions.

Installation

Do this to install dependencies:

$ cd tile-fetcher
$ npm install

Options

You specify the bounding box, levels, style, etc. through command line arguments to the script. Do node index.js --help to see the options. Here are the required options:

Option	Description
--style <Style name>	The map style name, as it appears in the Tileserver GL tile URL, e.g. klokantech-basic-cpb.
--level <Zoom level(s)>	Zoom level(s) to fetch. Must be in the range [0,14]. Specify multiple levels as a comma-delimted list, a range, or a combination of the two.
--dir <Output directory>	Directory in which tiles will be saved.

Here are the optional options:

Option	Description
--west <West longitude>	The west longitude of the bounding box to fetch. Defaults to -180 if unspecified.
--east <East longitude>	The east longitude of the bounding box to fetch. Defaults to 179.9999999999999 if unspecified.
--north <North latitude>	The north latitude of the bounding box to fetch. Defaults to 85.0511 if unspecified.
--south <South latitude>	The south latitude of the bounding box to fetch. Defaults to -85.0511 if unspecified.
--n <Num tile fetchers>	Number of tile fetchers to use. Defaults to 6 if unspecified.
--host <Tile server host>	Host name of the tile server. Defaults to localhost if unspecified.
--port <Tile server port>	Port number of the tile server. Defaults to 8080 if unspecified.
--start <x,y>	Start at the tile specified by the given x and y. This option is ignored if more than one level is specified.
--retina	Fetch retina tiles
--dry-run	Don't actually fetch tiles, just compute what tiles would be fetched and print the results.

Running

Here's an example for generating and fetching levels 0-8 for the entire Earth using the klokantech-basic-cpb style (this is assuming you have Tileserver GL running with the tileserver-gl-config-planet.json and listening on port 8080, as shown above):

$ node index.js --style klokantech-basic-cpb  --dir ./tiles/klokantech-basic-cpb --level 0-8

This will fetch retina tiles for levels 1-4 and levels 7 and 9 for the United States using the dark-matter-cpb style, assuming Tileserver GL is listening on port 8081:

$ node index.js --style dark-matter-cpb  --dir ./tiles/dark-matter-cpb@2x --level 1-4,7,9 --port 8081 --west -125.3321 --east -65.7421 --south 23.8991 --north 49.4325 --retina

For zoom levels having more than 20 tiles, you'll get a progress report approximately every 5%.

Since Tileserver GL seems to crash on me fairly often when I'm running multiple instances, it's handy to be able to start tile fetches somewhere in the middle of a level so I can resume where it crashed. You can optionally specify the starting tile by providing the --start option, e.g. to start at tile with x=10 and y=32:

$ node index.js --style klokantech-basic-cpb  --dir ./tiles/klokantech-basic-cpb --level 6 --start 10,32

The above command would fetch only 2038 of the 4096 tiles in level 6.

Note that the starting tile option is only honored when requesting a single level.

Viewing Tiles

Once you have some tiles generated and fetched, you can preview them using the tile-viewer.html file (also in the tile-fetcher directory), which you may need to edit according to where you saved your tiles.