Extend Mapbox Boundaries
Familiarity with front-end development, command line tools, and GIS. Access to Mapbox Boundaries.
Access to the Mapbox Boundaries tilesets is controlled by Mapbox account access token. If you do not have access on your account, contact Mapbox sales to request access to Boundaries tilesets.
Mapbox Boundaries includes coverage for most boundaries of the world, but in some cases you may want additional boundaries like school districts, community areas, or sub-market boundaries for your customers. You can extend Mapbox Boundaries with any custom polygon data and deliver the same frontend, API-driven services for data visualization, analysis, and geofencing applications around the world.
This guide walks through how to format, tile, and host additional boundary data to work in your application alongside Mapbox Boundaries.
Here are a few resources you'll need throughout this tutorial:
- Access to Mapbox Boundaries. Access to the Mapbox Boundaries tilesets is controlled by your Mapbox account access token. To request access to Mapbox Boundaries, contact Mapbox sales.
Data. In this tutorial, you will work with the school district boundaries produced by the US Government. Download the composite 2019 US School District Boundaries shapefile from the National Center for Education Statistics website.
- Note: The process outlined in this guide requires that your custom data uses polygon or multi-polygon geometries.
- QGIS. QGIS is an open source GIS application. You can download it from http://www.qgis.org/. You should be familiar with the QGIS interface before starting this tutorial.
- Tippecanoe. Tippecanoe is a command line tool for creating Mapbox tilesets.
- Mapbox CLI. You'll use the Mapbox CLI (command line interface) to upload the tileset you create with Tippecanoe to your Mapbox account.
You'll do two things to prepare the boundary data before creating Mapbox tilesets:
- Identify which feature properties in the shapefile will be useful in the final tiles and format those properties in preparation for tile creation.
- Generate polygon and point GeoJSON layers so that the data can be converted to polygon and point vector tiles using Tippecanoe.
Before you convert custom data into vector tiles, it is important to identify which feature properties will be useful in the final tileset and include only those useful properties to keep the tiles small and performant. In most cases, you will want the resulting tileset to include at least these two properties:
feature_id: A unique integer property can be used to filter and target individual features using GL feature states. This can be either randomly generated or be derived from an official code in the data.
nameAn optional text property that can be used add human readable labels to boundary features on the map.
Open the shapefile in QGIS and use the identify tool to inspect the available properties that can be used as a unique identifier.
GEOID property appears to be unique to each feature so you'll use this as a
feature_id. And, use the
NAME property for the
name. For convenience, it's useful to edit the property names since they cannot be modified later.
It is necessary that the boundary data is saved as a GeoJSON file with
EPSG:4326 (WGS84) projection before it can be converted into vector tiles with Tippecanoe.
- Right click the shapefile in the layer panel and select
Save Features As.
- Choose the
GeoJSONformat and the CRS as
- Only select the properties that you wish to export.
- Export the file to
Additionally, we will also generate a point GeoJSON from the centroid of every feature which are useful for locating the boundary labels on the map.
- Open the QGIS processing toolbox from the menu.
- Open the
Point on Surfacealgorithm.
- Choose the previously exported
us-school-district-polygonsas the input layer.
- Export the file to
You should now have two GeoJSON files,
us-school-district-points.geojson, that you'll use to generate the school district vector tiles.
If you notice geometry errors during any of the processing steps, use the
Fix Geometries algorithm from the QGIS processing toolbox to fix any issues with the input data.
To create tilesets from your custom data, use the command line tool Tippecanoe to transform your GeoJSON features to vector tiles. You'll need to create two source layers and merge them together into a single tileset source:
- One source layer for all polygons.
- One source layer for centroid points.
Tippecanoe has various settings that can control the conversion of the GeoJSON into the vector tiles. The most important settings are:
--minimum-zoomlevel controls the starting zoom at which the features are visible on the map. Use
2for a country level dataset and higher numbers like
8for a city level dataset.
--maximum-zoomlevel for the tiles which controls the maximum accuracy. The default is
14, which gives an accuracy of around 4 meters. For boundaries, a maximum zoom of
12is more appropriate.
- The source
--layername which needs to be unique amongst all the data sources added to the map.
--outputfile name for the vector tiles in MBTiles format.
--drop-ratewhich controls how many points are dropped at low zoom levels. Use
0to ensure least points are dropped.
- The property that we wish to be used for the unique feature id in the tiles can be set using
--convert-stringified-ids-to-numbersto ensure that they are converted to integers first. For the school boundaries we will use the
feature_idproperty. Alternatively if you wish to generate a new unique identifier, you can use the
- Set the
--simplificationscale to simplify complex polygon geometries for more optimized tiles.
There is fixed limit to the amount of data that can be stored into a vector tile. Depending on your use case, you may want to adjust the starting zoom level at which te data is visible
-Z, the simplification or the number of feature attributes to control how many features you can efficiently pack into a tile.
Start by creating a polygon source layer. Use the following Tippecanoe command to transform the example files. We will use a simplification scale of
8 which is a good starting value (use a lower number if more details are required):
tippecanoe -f --output=us-school-district-polygons.mbtiles --layer=us_school_districts --minimum-zoom=2 --maximum-zoom=12 --simplification=8 --use-attribute-for-id=feature_id --convert-stringified-ids-to-numbers us-school-district-polygons.geojson
Next, create a point source layer using the following Tippecanoe command. We can use a lower minimum zoom level of
1 for points for it to be visible even when zoomed out beyond the country:
tippecanoe -f --output=us-school-district-points.mbtiles --layer=us_school_districts_points --minimum-zoom=1 --maximum-zoom=12 --drop-rate=0 --use-attribute-for-id=feature_id --convert-stringified-ids-to-numbers us-school-district-points.geojson
Then, join the polygon and point layers into one vector tileset using the following command:
tile-join -f --output=us-school-district.mbtiles us-school-district-polygons.mbtiles us-school-district-points.mbtiles
You can optionally inspect the final MBTiles locally using
mbview to confirm it has the expected features and attributes:
You can upload your tileset to your Mapbox account using Mapbox Studio. After the uploading has finished processing in Mapbox Studio, a tileset ID is generated automatically for you.
Alternatively, you can upload your tileset from the command line using the Uploads API. The API also gives control over setting a custom tileset ID.
Here is an example style showing how the new US Admin Level 3 data works alongside the base Mapbox Boundaries product.
Learn more about how you can use Mapbox Boundaries:
- Point-in-polygon query with Mapbox Boundaries: Determine what polygons exist at a single point using the Mapbox Tilequery API.
- Data-joins with Mapbox Boundaries: The data-join technique involves inner joins between local data, such as the unemployment rate by US state, to vector tile features, such as admin boundaries in Mapbox Boundaries, using data-driven style notation.