A feature layer is a dataset in a hosted feature service. Each feature layer contains features with a single geometry type (point, line, or polygon), and a set of attributes. You can access and display features by making query requests to the feature service and displaying them in a map.
In this tutorial, you access the Trailheads feature layer to get GeoJSON and display the features as clusters. Working with GeoJSON is often useful for dynamically generated data, but not suitable for large datasets.
Prerequisites
You need a free ArcGIS developer account to access your dashboard and API keys. The API key must be scoped to access the services used in this tutorial.
<!DOCTYPE html><html><head><metacharset="utf-8" /><metaname="viewport"content="initial-scale=1,maximum-scale=1,user-scalable=no" /><scriptsrc="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.js"></script><linkhref="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.css"rel="stylesheet" /><scriptsrc="https://unpkg.com/@esri/arcgis-rest-request@3.0.0/dist/umd/request.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-auth@3.0.0/dist/umd/auth.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-feature-layer@3.0.0/dist/umd/feature-layer.umd.js"></script><style>html,
body,
#map {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
font-family: Arial, Helvetica, sans-serif;
font-size: 14px;
color: #323232;
}
</style></head><body><divid="map"></div><script>const apiKey = "YOUR-API-KEY";
const basemapEnum = "ArcGIS:Streets";
const map = new mapboxgl.Map({
container: "map", // the id of the div element style: `https://basemaps-api.arcgis.com/arcgis/rest/services/styles/${basemapEnum}?type=style&apiKey=${apiKey}`,
zoom: 12, // starting zoom center: [-118.805, 34.027] // starting location [longitude, latitude] });
map.once("load", () => {
// This code runs once the base style has finished loading. map.addSource("trailheads", {
type: "geojson",
data: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0/query?f=pgeojson&where=1=1",
cluster: true,
clusterRadius: 20, // cluster two trailheads if less than 20 pixels apart clusterMaxZoom: 14// display all trailheads individually from zoom 14 up });
map.addLayer({
id: "trailheads-circle",
type: "circle",
source: "trailheads",
paint: {
"circle-color": "hsla(0,0%,0%,0.75)",
"circle-stroke-width": 1.5,
"circle-stroke-color": "white",
"circle-radius": ["case", ["get", "cluster"], 10, 5] // 10 pixels for clusters, 5 pixels otherwise }
});
map.addLayer({
id: "trailheads-cluster-count",
type: "symbol",
source: "trailheads",
layout: {
"text-font": ["Arial Bold"],
"text-field": ["get", "point_count"],
"text-offset": [0, 0.1] // move the label vertically downwards slightly to improve centering },
paint: {
"text-color": "white" }
});
});
</script></body></html>
Add a GeoJSON source
To add GeoJSON from a feature service, you need to define a source of type geojson and reference the feature layer. The source tells Mapbox GL JS how to access the data for the layer, but does not visually add it to the map. To get GeoJSON features from a feature layer, you provide a URL to query the feature service and return features in GeoJSON format. Features can then be displayed by adding the source to a layer.
While there are several types of sources, the two most common are geojson (for a set of features represented as GeoJSON) and vector (for vector tiles). For more information, see the Mapbox GL JS Style Specification.
Inside the load event handler, add a source. Set the id to trailheads and type to geojson. Set data to the URL for the trailheads feature layer. Append query?f=pgeojson&where=1=1 to the URL to request all of the features as GeoJSON.
Add line.Add line.Add line.Add line.Add line.
<!DOCTYPE html><html><head><metacharset="utf-8" /><metaname="viewport"content="initial-scale=1,maximum-scale=1,user-scalable=no" /><scriptsrc="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.js"></script><linkhref="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.css"rel="stylesheet" /><scriptsrc="https://unpkg.com/@esri/arcgis-rest-request@3.0.0/dist/umd/request.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-auth@3.0.0/dist/umd/auth.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-feature-layer@3.0.0/dist/umd/feature-layer.umd.js"></script><style>html,
body,
#map {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
font-family: Arial, Helvetica, sans-serif;
font-size: 14px;
color: #323232;
}
</style></head><body><divid="map"></div><script>const apiKey = "YOUR-API-KEY";
const basemapEnum = "ArcGIS:Streets";
const map = new mapboxgl.Map({
container: "map", // the id of the div element style: `https://basemaps-api.arcgis.com/arcgis/rest/services/styles/${basemapEnum}?type=style&apiKey=${apiKey}`,
zoom: 12, // starting zoom center: [-118.805, 34.027] // starting location [longitude, latitude] });
map.once("load", () => {
// This code runs once the base style has finished loading. map.addSource("trailheads", {
type: "geojson",
data: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0/query?f=pgeojson&where=1=1",
cluster: true,
clusterRadius: 20, // cluster two trailheads if less than 20 pixels apart clusterMaxZoom: 14// display all trailheads individually from zoom 14 up });
map.addLayer({
id: "trailheads-circle",
type: "circle",
source: "trailheads",
paint: {
"circle-color": "hsla(0,0%,0%,0.75)",
"circle-stroke-width": 1.5,
"circle-stroke-color": "white",
"circle-radius": ["case", ["get", "cluster"], 10, 5] // 10 pixels for clusters, 5 pixels otherwise }
});
map.addLayer({
id: "trailheads-cluster-count",
type: "symbol",
source: "trailheads",
layout: {
"text-font": ["Arial Bold"],
"text-field": ["get", "point_count"],
"text-offset": [0, 0.1] // move the label vertically downwards slightly to improve centering },
paint: {
"text-color": "white" }
});
});
</script></body></html>
Add a circle layer
A layer in Mapbox GL JS is a visual representation of the data within one source. Use a layer of type circle to display the trailheads.
Use addLayer to add a circle layer with id trailheads-circle. Set source to trailheads to reference the source you just created. Add paint properties to make the circles black.
The type property defines how it will be displayed. Commonly used layer types include circle, line, fill and symbol (used for text and icons).
The id property is an identifier you choose. You will need it if you want to manipulate the layer, such as hiding it or changing its properties dynamically.
The source property references the id property of the source you just created.
The paint properties control the visual attributes of the layer and are specific to the type of layer.
<!DOCTYPE html><html><head><metacharset="utf-8" /><metaname="viewport"content="initial-scale=1,maximum-scale=1,user-scalable=no" /><scriptsrc="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.js"></script><linkhref="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.css"rel="stylesheet" /><scriptsrc="https://unpkg.com/@esri/arcgis-rest-request@3.0.0/dist/umd/request.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-auth@3.0.0/dist/umd/auth.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-feature-layer@3.0.0/dist/umd/feature-layer.umd.js"></script><style>html,
body,
#map {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
font-family: Arial, Helvetica, sans-serif;
font-size: 14px;
color: #323232;
}
</style></head><body><divid="map"></div><script>const apiKey = "YOUR-API-KEY";
const basemapEnum = "ArcGIS:Streets";
const map = new mapboxgl.Map({
container: "map", // the id of the div element style: `https://basemaps-api.arcgis.com/arcgis/rest/services/styles/${basemapEnum}?type=style&apiKey=${apiKey}`,
zoom: 12, // starting zoom center: [-118.805, 34.027] // starting location [longitude, latitude] });
map.once("load", () => {
// This code runs once the base style has finished loading. map.addSource("trailheads", {
type: "geojson",
data: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0/query?f=pgeojson&where=1=1",
cluster: true,
clusterRadius: 20, // cluster two trailheads if less than 20 pixels apart clusterMaxZoom: 14// display all trailheads individually from zoom 14 up });
map.addLayer({
id: "trailheads-circle",
type: "circle",
source: "trailheads",
paint: {
"circle-color": "hsla(0,0%,0%,0.75)",
"circle-stroke-width": 1.5,
"circle-stroke-color": "white",
"circle-radius": ["case", ["get", "cluster"], 10, 5] // 10 pixels for clusters, 5 pixels otherwise }
});
map.addLayer({
id: "trailheads-cluster-count",
type: "symbol",
source: "trailheads",
layout: {
"text-font": ["Arial Bold"],
"text-field": ["get", "point_count"],
"text-offset": [0, 0.1] // move the label vertically downwards slightly to improve centering },
paint: {
"text-color": "white" }
});
});
</script></body></html>
At the top right, click Run to display the basemap with trailheads as black dots.
Use clusters to display points
One benefit of using GeoJSON to load points in Mapbox GL JS is you can use clustering. This technique replaces a number of overlapping points with a single point that represents the cluster. It simplifies the visual appearance of the map by reducing detail, particularly at lower zoom levels.
To enable clustering, you pass additional parameters when defining the source: cluster: true and the optional parameters clusterRadius and clusterMaxZoom.
Points that represent clusters have a cluster property that is set to true. You can use this in your trailheads-circle layer to make those points larger, by using a data-driven expression for circle-radius. You use the case and get expressions for this.
They also have a point_count attribute which contains the number of points in the cluster. You can display this as a text label, using a symbol layer.
Add cluster, clusterRadius and clusterMaxZoom attributes to the definition of the trailheads source.
Add line.Add line.Add line.
<!DOCTYPE html><html><head><metacharset="utf-8" /><metaname="viewport"content="initial-scale=1,maximum-scale=1,user-scalable=no" /><scriptsrc="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.js"></script><linkhref="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.css"rel="stylesheet" /><scriptsrc="https://unpkg.com/@esri/arcgis-rest-request@3.0.0/dist/umd/request.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-auth@3.0.0/dist/umd/auth.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-feature-layer@3.0.0/dist/umd/feature-layer.umd.js"></script><style>html,
body,
#map {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
font-family: Arial, Helvetica, sans-serif;
font-size: 14px;
color: #323232;
}
</style></head><body><divid="map"></div><script>const apiKey = "YOUR-API-KEY";
const basemapEnum = "ArcGIS:Streets";
const map = new mapboxgl.Map({
container: "map", // the id of the div element style: `https://basemaps-api.arcgis.com/arcgis/rest/services/styles/${basemapEnum}?type=style&apiKey=${apiKey}`,
zoom: 12, // starting zoom center: [-118.805, 34.027] // starting location [longitude, latitude] });
map.once("load", () => {
// This code runs once the base style has finished loading. map.addSource("trailheads", {
type: "geojson",
data: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0/query?f=pgeojson&where=1=1",
cluster: true,
clusterRadius: 20, // cluster two trailheads if less than 20 pixels apart clusterMaxZoom: 14// display all trailheads individually from zoom 14 up });
map.addLayer({
id: "trailheads-circle",
type: "circle",
source: "trailheads",
paint: {
"circle-color": "hsla(0,0%,0%,0.75)",
"circle-stroke-width": 1.5,
"circle-stroke-color": "white",
"circle-radius": ["case", ["get", "cluster"], 10, 5] // 10 pixels for clusters, 5 pixels otherwise }
});
map.addLayer({
id: "trailheads-cluster-count",
type: "symbol",
source: "trailheads",
layout: {
"text-font": ["Arial Bold"],
"text-field": ["get", "point_count"],
"text-offset": [0, 0.1] // move the label vertically downwards slightly to improve centering },
paint: {
"text-color": "white" }
});
});
</script></body></html>
Make each point larger if it represents a cluster.
Add line.
<!DOCTYPE html><html><head><metacharset="utf-8" /><metaname="viewport"content="initial-scale=1,maximum-scale=1,user-scalable=no" /><scriptsrc="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.js"></script><linkhref="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.css"rel="stylesheet" /><scriptsrc="https://unpkg.com/@esri/arcgis-rest-request@3.0.0/dist/umd/request.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-auth@3.0.0/dist/umd/auth.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-feature-layer@3.0.0/dist/umd/feature-layer.umd.js"></script><style>html,
body,
#map {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
font-family: Arial, Helvetica, sans-serif;
font-size: 14px;
color: #323232;
}
</style></head><body><divid="map"></div><script>const apiKey = "YOUR-API-KEY";
const basemapEnum = "ArcGIS:Streets";
const map = new mapboxgl.Map({
container: "map", // the id of the div element style: `https://basemaps-api.arcgis.com/arcgis/rest/services/styles/${basemapEnum}?type=style&apiKey=${apiKey}`,
zoom: 12, // starting zoom center: [-118.805, 34.027] // starting location [longitude, latitude] });
map.once("load", () => {
// This code runs once the base style has finished loading. map.addSource("trailheads", {
type: "geojson",
data: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0/query?f=pgeojson&where=1=1",
cluster: true,
clusterRadius: 20, // cluster two trailheads if less than 20 pixels apart clusterMaxZoom: 14// display all trailheads individually from zoom 14 up });
map.addLayer({
id: "trailheads-circle",
type: "circle",
source: "trailheads",
paint: {
"circle-color": "hsla(0,0%,0%,0.75)",
"circle-stroke-width": 1.5,
"circle-stroke-color": "white",
"circle-radius": ["case", ["get", "cluster"], 10, 5] // 10 pixels for clusters, 5 pixels otherwise }
});
map.addLayer({
id: "trailheads-cluster-count",
type: "symbol",
source: "trailheads",
layout: {
"text-font": ["Arial Bold"],
"text-field": ["get", "point_count"],
"text-offset": [0, 0.1] // move the label vertically downwards slightly to improve centering },
paint: {
"text-color": "white" }
});
});
</script></body></html>
Add a symbol layer, trailheads-cluster-count. Use the attribute point_count as the value for text-field.
<!DOCTYPE html><html><head><metacharset="utf-8" /><metaname="viewport"content="initial-scale=1,maximum-scale=1,user-scalable=no" /><scriptsrc="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.js"></script><linkhref="https://api.tiles.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.css"rel="stylesheet" /><scriptsrc="https://unpkg.com/@esri/arcgis-rest-request@3.0.0/dist/umd/request.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-auth@3.0.0/dist/umd/auth.umd.js"></script><scriptsrc="https://unpkg.com/@esri/arcgis-rest-feature-layer@3.0.0/dist/umd/feature-layer.umd.js"></script><style>html,
body,
#map {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
font-family: Arial, Helvetica, sans-serif;
font-size: 14px;
color: #323232;
}
</style></head><body><divid="map"></div><script>const apiKey = "YOUR-API-KEY";
const basemapEnum = "ArcGIS:Streets";
const map = new mapboxgl.Map({
container: "map", // the id of the div element style: `https://basemaps-api.arcgis.com/arcgis/rest/services/styles/${basemapEnum}?type=style&apiKey=${apiKey}`,
zoom: 12, // starting zoom center: [-118.805, 34.027] // starting location [longitude, latitude] });
map.once("load", () => {
// This code runs once the base style has finished loading. map.addSource("trailheads", {
type: "geojson",
data: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/FeatureServer/0/query?f=pgeojson&where=1=1",
cluster: true,
clusterRadius: 20, // cluster two trailheads if less than 20 pixels apart clusterMaxZoom: 14// display all trailheads individually from zoom 14 up });
map.addLayer({
id: "trailheads-circle",
type: "circle",
source: "trailheads",
paint: {
"circle-color": "hsla(0,0%,0%,0.75)",
"circle-stroke-width": 1.5,
"circle-stroke-color": "white",
"circle-radius": ["case", ["get", "cluster"], 10, 5] // 10 pixels for clusters, 5 pixels otherwise }
});
map.addLayer({
id: "trailheads-cluster-count",
type: "symbol",
source: "trailheads",
layout: {
"text-font": ["Arial Bold"],
"text-field": ["get", "point_count"],
"text-offset": [0, 0.1] // move the label vertically downwards slightly to improve centering },
paint: {
"text-color": "white" }
});
});
</script></body></html>
Run the app
In CodePen, run your code to display the map.
The map should display the trailheads as clusters with a number on a large circle. Zoom in to see the clusters split into smaller clusters, and eventually split into single trailhead features.
