Request route polylines

The computeRoutes method (REST) and the ComputeRoutes method (gRPC) both return the route represented by a polyline as part of the response. These APIs return two types of polylines:

  • Basic polyline (default), represents a route but without traffic information embedded in the polyline. Requests that return a basic polyline are billed at the Routes Basic rate. Learn more about billing for Routes API.

  • Traffic-aware polyline, contain information about the traffic conditions along the route. Traffic conditions are expressed in terms of speed categories (NORMAL, SLOW, TRAFFIC_JAM) applicable on a given interval of the polyline. Requests for traffic-aware polylines are billed at the Routes Preferred rate. Learn more about billing for Routes API. For details, see Configure polyline quality

For more on polylines, see:

Request a basic polyline for a route, leg, or step

A polyline is represented by a Polyline (REST) or Polyline (gRPC) object. You can return a polyline in the response at the route, leg, and step level.

Specify which polyline to return by using the response field mask:

  • At the route level, return a polyline in the response by including routes.polyline in the response field mask.

  • At the leg level, return a polyline in the response for each leg of the route by including routes.legs.polyline.

  • At the step level, return a polyline in the response for each step of the leg by including routes.legs.steps.polyline.

For example, to return a polyline for the entire route, for each leg, and for each step of each leg:

curl -X POST -d '{
  "origin":{
    "address": "1600 Amphitheatre Parkway, Mountain View, CA"
  },
  "destination":{
    "address": "24 Willie Mays Plaza, San Francisco, CA 94107"
  },
  "travelMode": "DRIVE"
}' \
-H 'Content-Type: application/json' \
-H 'X-Goog-Api-Key: YOUR_API_KEY' \
-H 'X-Goog-FieldMask: routes.duration,routes.distanceMeters,routes.polyline,routes.legs.polyline,routes.legs.steps.polyline' \
'https://routes.googleapis.com/directions/v2:computeRoutes'

This request returns the following response which includes the polyline for the route, for each leg of the route, and for each step of the leg:

{
  "routes": [
    {
      "legs": [
        {
          "polyline": {
              "encodedPolyline": "ipkcFfich...@Bs@?A?O?SD{A@o@B}@I?qA?_AA_@@_@?"
          }
        },
          "steps": [
              {
                  "polyline": {
                      "encodedPolyline": "kclcF...@sC@YIOKI"
                  }
              },
              {
                  "polyline": {
                      "encodedPolyline": "wblcF~...SZSF_@?"
                  }
              },
              ...
      ],
      "distanceMeters": 56901,
      "duration": "2420s",
      "polyline": {
        "encodedPolyline": "ipkcFfich...@Bs@?A?O?SD{A@o@B}@I?qA?_AA_@@_@?"
      }
    }
  ]
}

Because this request only contains an origin and a destination, the returned route only contains a single leg. Therefore, the polyline for the leg and for the route are the same.

If you add an intermediate waypoint to the request, then the returned route contains two legs:

curl -X POST -d '{
  "origin":{
    "address": "1600 Amphitheatre Parkway, Mountain View, CA"
  },
  "destination":{
    "address": "24 Willie Mays Plaza, San Francisco, CA 94107"
  },
  "intermediates": [
    { "address": "450 Serra Mall, Stanford, CA 94305, USA"},
  ],
  "travelMode": "DRIVE",
}' \
-H 'Content-Type: application/json' \
-H 'X-Goog-Api-Key: YOUR_API_KEY' \
-H 'X-Goog-FieldMask: routes.duration,routes.distanceMeters,routes.polyline,routes.legs.polyline' \
'https://routes.googleapis.com/directions/v2:computeRoutes'

This request returns two legs, each with a unique polyline, and a polyline for the entire route:

{
  "routes": [
    {
      "legs": [
        {
          "polyline": {
            "encodedPolyline": "kclcFfqchV?A...?I@G?GAECCCEKICBAFG"
          }
          "steps": [
            {
                "polyline": {
                    "encodedPolyline": "kclcFfqch...YIOKI"
                }
            },
        ...
        },
        {
          "polyline": {
            "encodedPolyline": "ojmcFtethV?K...QOYQOGA?_@MUG[Ga@G"
          }
          "steps": [
            {
                "polyline": {
                    "encodedPolyline": "uypeFbo`jVgJq...PoBiC"
                }
            },
        ...
        }
      ],
      "distanceMeters": 68403,
      "duration": "3759s",
      "polyline": {
          "encodedPolyline": "kclcFfqchV?A?CBKF[Ha...?GAECCCEKICBAFGJEBE"
      }
    }
  ]
}

Polyline quality

The quality of a polyline can be described in the following terms:

  • The floating-point precision of the points

    Points are specified as latitude and longitude values, which are represented in single-precision floating-point format. This works well for small values (which can be represented precisely), but precision decreases as values increase because of floating-point rounding errors.

    In computeRoutes method (REST) and ComputeRoutes, this is controlled by polylineEncoding.

  • The number of points that make up the polyline

    The more points there are, the smoother the polyline (especially in curves).

    In computeRoutes method (REST) and ComputeRoutes, this is controlled by polylineQuality.

Configure polyline encoding type

Use the polylineEncoding request option for controlling the polyline type. The polylineEncoding property controls whether the polyline will be encoded as ENCODED_POLYLINE (default), meaning the Encoded Polyline Algorithm Format will be used, or GEO_JSON_LINESTRING, meaning the GeoJSON LineString format will be used.

For example, in the request body:

curl -X POST -d '{
  "origin":{
    "address": "1600 Amphitheatre Parkway, Mountain View, CA"
  },
  "destination":{
    "address": "24 Willie Mays Plaza, San Francisco, CA 94107"
  },
  "travelMode": "DRIVE",
  "polylineEncoding": "ENCODED_POLYLINE"
}' \
-H 'Content-Type: application/json' \
-H 'X-Goog-Api-Key: YOUR_API_KEY' \
-H 'X-Goog-FieldMask: routes.duration,routes.distanceMeters,routes.polyline,routes.legs.polyline' \
'https://routes.googleapis.com/directions/v2:computeRoutes'

Configure Polyline quality

polylineQuality specifies the quality of the polyline as HIGH_QUALITY or OVERVIEW (default). With OVERVIEW, the polyline is composed using a small number of points and has a lower request latency than HIGH_QUALITY.

For example, in the request body:

{
  "origin":{
    "location":{
      "latLng":{
        "latitude": 37.419734,
        "longitude": -122.0827784
      }
    }
  },
  "destination":{
    "location":{
      "latLng":{
        "latitude": 37.417670,
        "longitude": -122.079595
      }
    }
  },
  "travelMode": "DRIVE",
  "routingPreference": "TRAFFIC_AWARE",
  "polylineQuality": "HIGH_QUALITY",
  "polylineEncoding": "ENCODED_POLYLINE",
  "departureTime": "2023-10-15T15:01:23.045123456Z",
  ...
}

Request a traffic-aware polyline

The examples shown above all return basic polylines, meaning polylines without traffic information. In addition, you can also request that the polyline contains traffic information for the route and for each leg of the route.

Traffic-aware polylines contain information about the traffic conditions along the route. Traffic conditions are expressed in terms of speed categories (NORMAL, SLOW, TRAFFIC_JAM) for a given interval of the response polyline. The intervals are defined by the indexes of their starting (inclusive) and ending (exclusive) polyline points.

For example, the following response shows NORMAL traffic between polyline points 2 and 4:

{
  "startPolylinePointIndex": 2,
  "endPolylinePointIndex": 4,
  "speed": "NORMAL"
}

To make a request to compute a traffic-aware polyline, set the following properties in the request:

  • Set the extraComputations array field to TRAFFIC_ON_POLYLINE to enable the traffic calculation.

  • Set the travelMode to DRIVE or TWO_WHEELER. Requests for any other travel mode return an error.

  • Specify either the TRAFFIC_AWARE or TRAFFIC_AWARE_OPTIMAL routing preference in the request. For more information, see Configure quality vs latency.

  • Set a response field mask that specifies to return the response properties:

    • At the route level, return all travel information in the response by including routes.travelAdvisory in the response field mask. To return just the traffic information, specify routes.travelAdvisory.speedReadingIntervals

    • At the leg level, return all travel information in the response for each leg of the route by including routes.legs.travelAdvisory. To return just the traffic information, specify routes.legs.travelAdvisory.speedReadingIntervals.

curl -X POST -d '{
  "origin":{
    "address": "1600 Amphitheatre Parkway, Mountain View, CA"
  },
  "destination":{
    "address": "24 Willie Mays Plaza, San Francisco, CA 94107"
  },
  "travelMode": "DRIVE",
  "extraComputations": ["TRAFFIC_ON_POLYLINE"],
  "routingPreference": "TRAFFIC_AWARE_OPTIMAL"
}' \
-H 'Content-Type: application/json' \
-H 'X-Goog-Api-Key: YOUR_API_KEY' \
-H 'X-Goog-FieldMask: routes.duration,routes.distanceMeters,routes.polyline,routes.legs.polyline,routes.travelAdvisory,routes.legs.travelAdvisory' \
'https://routes.googleapis.com/directions/v2:computeRoutes'

Example response for a traffic-aware polyline

In the response, traffic data is encoded in the polyline and is contained in the travelAdvisory field, of type RouteLegTravelAdvisory object (each leg) and RouteTravelAdvisory object (route).

For example:

{
  "routes": [
    {
      "legs": {
        "polyline": {
          "encodedPolyline": "}boeF~zbjVAg@EmB`GWHlD"
        },
        // Traffic data for the leg.
        "travelAdvisory": {
          "speedReadingIntervals": [
            {
              "endPolylinePointIndex": 1,
              "speed": "NORMAL"
            },
            {
              "startPolylinePointIndex": 1,
              "endPolylinePointIndex": 2,
              "speed": "SLOW"
            },
            {
              "startPolylinePointIndex": 2,
              "endPolylinePointIndex": 4,
              "speed": "NORMAL"
            }
          ] 
        }
      },
      "polyline": {
        "encodedPolyline": "}boeF~zbjVAg@EmB`GWHlD"
      },
      // Traffic data for the route.
      "travelAdvisory": {
        "speedReadingIntervals": [
          {
            "endPolylinePointIndex": 1,
            "speed": "NORMAL"
          },
          {
            "startPolylinePointIndex": 1,
            "endPolylinePointIndex": 2,
            "speed": "SLOW"
          },
          {
            "startPolylinePointIndex": 2,
            "endPolylinePointIndex": 4,
            "speed": "NORMAL"
          }
        ] 
      }
    }
  ]
}

Both RouteTravelAdvisory and RouteLegTravelAdvisory include an array field called speedReadingIntervals that contains traffic speed information. Each object in the array is represented by a SpeedReadingInterval (REST) or SpeedReadingInterval (gRPC) object.

A SpeedReadingInterval object includes speed reading for a route interval, such as NORMAL, SLOW, or TRAFFIC_JAM. The entire array of objects covers the entire polyline of the route without overlap. The start point of a specified interval is the same as the end point of the preceding interval.

Every interval is described by its startPolylinePointIndex, endPolylinePointIndex, and the corresponding speed category. Notice that the lack of start index within the interval corresponds with index 0 in accordance with the proto3 practices.

The startPolylinePointIndex and endPolylinePointIndex values are not always consecutive. For example:

{
  "startPolylinePointIndex": 2,
  "endPolylinePointIndex": 4,
  "speed": "NORMAL"
}

In this case, the traffic conditions were the same from index 2 to index 4.

Render traffic-aware polylines with Maps SDK

We recommend displaying traffic aware polylines on the map using the various features offered by Google Maps SDKs including custom coloring, strokes, and patterns along the polyline stretches. For more details about using polylines, see Polyline Features for Android and Polyline Features for iOS.

Example Polyline rendering

The users of Maps SDK have the opportunity of defining a customized mapping logic between the speed categories and the polyline rendering schemas. As an example, one might decide to display "NORMAL" speed as a thick blue line on the map while "SLOW" speed might be displayed as a thick orange line, for example.

The following snippets add a thick blue polyline with geodesic segments from Melbourne to Perth. For more information, see Customizing appearances (for Android) and Customize the Polyline (for iOS).

Android

Java

Polyline line = map.addPolyline(new PolylineOptions()
    .add(new LatLng(-37.81319, 144.96298), new LatLng(-31.95285, 115.85734))
    .width(25)
    .color(Color.BLUE)
    .geodesic(true));

Kotlin

val line: Polyline = map.addPolyline(
  PolylineOptions()
    .add(LatLng(-37.81319, 144.96298), LatLng(-31.95285, 115.85734))
    .width(25f)
    .color(Color.BLUE)
    .geodesic(true)
)

iOS

Objective-C

GMSMutablePath *path = [GMSMutablePath path];
[path addLatitude:-37.81319 longitude:144.96298];
[path addLatitude:-31.95285 longitude:115.85734];
GMSPolyline *polyline = [GMSPolyline polylineWithPath:path];
polyline.strokeWidth = 10.f;
polyline.strokeColor = .blue;
polyline.geodesic = YES;
polyline.map = mapView;

Swift

let path = GMSMutablePath()
path.addLatitude(-37.81319, longitude: 144.96298)
path.addLatitude(-31.95285, longitude: 115.85734)
let polyline = GMSPolyline(path: path)
polyline.strokeWidth = 10.0
polyline.geodesic = true
polyline.map = mapView