Elevation Service

Overview

The Elevation service provides elevation data for locations on the surface of the earth, including depth locations on the ocean floor (which return negative values). In those cases where Google does not possess exact elevation measurements at the precise location you request, the service will interpolate and return an averaged value using the four nearest locations.

The ElevationService object provides you with a simple interface to query locations on the earth for elevation data. Additionally, you may request sampled elevation data along paths, allowing you to calculate the equidistant elevation changes along routes. The ElevationService object communicates with the Google Maps API Elevation Service which receives elevation requests and returns elevation data.

Note that these requests are rate-limited to discourage abuse of the service. If instead you wish to calculate elevations for static, known locations, see the Elevation Web Service documentation.

With the Elevation service, you can develop hiking and biking applications, mobile positioning applications, or low resolution surveying applications.

Getting started

Before using the Elevation service in the Google Maps JavaScript API, first ensure that the Google Maps Elevation API is enabled in the Google API Console, in the same project you set up for the Google Maps JavaScript API.

To view your list of enabled APIs:

  1. Go to the Google API Console Enabled APIs list.
  2. From the project drop-down, select your project.
  3. From the Enabled APIs list, look for Google Maps Elevation API.
  4. If you see the API in the list, you’re all set. If the API is not listed, enable it:
    1. Select the Google APIs tab.
    2. Search for Google Maps Elevation API, then select it from the results list.
    3. Select Enable. When the process finishes, Google Maps Elevation API appears in the list of enabled APIs.

Usage limits and policies

Quotas

The following usage limits are in place for the Elevation service:

Use of the Elevation service with the Standard Plan

  • 2,500 free requests per day, calculated as the sum of client-side and server-side queries; enable billing to access higher daily quotas, billed at $0.50 USD / 1000 additional requests, up to 100,000 requests daily.
  • 512 locations per request.
  • 50 requests per second, calculated as the sum of client-side and server-side queries combined.

Use of the Elevation service with the Premium Plan

  • Shared daily free quota of 100,000 requests per 24 hours; additional requests applied against the annual purchase of Maps APIs Credits.
  • 512 locations per request.
  • Unlimited client-side requests per second, per project. Note that the server-side API is limited to 50 requests per second.

Policies

Use of the Elevation service must be in accordance with the policies described for the Google Maps Elevation API.

Elevation Requests

Accessing the Elevation service is asynchronous, since the Google Maps API needs to make a call to an external server. For that reason, you need to pass a callback method to execute upon completion of the request. This callback method should process the result(s). Note that the Elevation service returns a status code (ElevationStatus) and an array of separate ElevationResult objects.

The ElevationService handles two types of requests:

  • Requests for separate, discrete locations using the getElevationForLocations() method, which is passed a list of one or more locations using a LocationElevationRequest object.
  • Requests for elevation on a series of connected points along a path using the getElevationAlongPath() method, which is passed an ordered set of path vertices within a PathElevationRequest object. When requesting elevations along paths, you must also pass a parameter indicating how many samples you wish to take along that path.

Each of these methods must also pass a callback method to handle the returned ElevationResult and ElevationStatus objects.

Location Elevation Requests

A LocationElevationRequest object literal contains the following field:

{
  locations[]: LatLng
}

locations (required) defines the location(s) on the earth from which to return elevation data. This parameter takes an array of LatLngs.

You may pass any number of multiple coordinates within an array, as long as you don't exceed the service quotas. Note that when passing multiple coordinates, the accuracy of any returned data may be of lower resolution than when requesting data for a single coordinate.

Sampled Path Elevation Requests

A PathElevationRequest object literal contains the following fields:

{
  path[]: LatLng,
  samples: Number
}

These fields are explained below:

  • path (required) defines a path on the earth for which to return elevation data. The path parameter defines a set of two or more ordered {latitude,longitude} pairs using an array of two or more LatLng objects.
  • samples (required) specifies the number of sample points along a path for which to return elevation data. The samples parameter divides the given path into an ordered set of equidistant points along the path.

As with positional requests, the path parameter specifies a set of latitude and longitude values. Unlike a positional request, however, the path specifies an ordered set of vertices. Rather than return elevation data at the vertices, path requests are sampled along the length of the path, where each sample is equidistant from each other (inclusive of the endpoints).

Elevation Responses

For each valid request, the Elevation service will return to the defined callback a set of ElevationResult objects along with an ElevationStatus object.

Elevation Statuses

Each elevation request returns an ElevationStatus code within its callback function. This status code will contain one of the following values:

  • OK indicating the service request was successful
  • INVALID_REQUEST indicating the service request was malformed
  • OVER_QUERY_LIMIT indicating that the requestor has exceeded quota
  • REQUEST_DENIED indicating the service did not complete the request, likely because on an invalid parameter
  • UNKNOWN_ERROR indicating an unknown error

You should check that your callback succeeded by examining this status code for google.maps.ElevationStatus.OK.

Elevation Results

Upon success, the results argument of your callback function will contain a set of ElevationResult objects. These objects contain the following elements:

  • A location element (containing LatLng objects) of the position for which elevation data is being computed. Note that for path requests, the set of location elements will contain the sampled points along the path.
  • An elevation element indicating the elevation of the location in meters.
  • A resolution value, indicating the maximum distance between data points from which the elevation was interpolated, in meters. This property will be missing if the resolution is not known. Note that elevation data becomes more coarse (larger resolution values) when multiple points are passed. To obtain the most accurate elevation value for a point, it should be queried independently.

Elevation Examples

The following code translates a click on a map into an elevation request using the LocationElevationRequest object:

function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 8,
    center: {lat: 63.333, lng: -150.5},  // Denali.
    mapTypeId: 'terrain'
  });
  var elevator = new google.maps.ElevationService;
  var infowindow = new google.maps.InfoWindow({map: map});

  // Add a listener for the click event. Display the elevation for the LatLng of
  // the click inside the infowindow.
  map.addListener('click', function(event) {
    displayLocationElevation(event.latLng, elevator, infowindow);
  });
}

function displayLocationElevation(location, elevator, infowindow) {
  // Initiate the location request
  elevator.getElevationForLocations({
    'locations': [location]
  }, function(results, status) {
    infowindow.setPosition(location);
    if (status === google.maps.ElevationStatus.OK) {
      // Retrieve the first result
      if (results[0]) {
        // Open the infowindow indicating the elevation at the clicked position.
        infowindow.setContent('The elevation at this point <br>is ' +
            results[0].elevation + ' meters.');
      } else {
        infowindow.setContent('No results found');
      }
    } else {
      infowindow.setContent('Elevation service failed due to: ' + status);
    }
  });
}

View example (elevation-simple.html).

The following example constructs a polyline given a set of coordinates and displays elevation data along that path using the Google Visualization API. (You must load this API using the Google Common Loader.) An elevation request is constructed using the PathElevationRequest:

// Load the Visualization API and the columnchart package.
google.load('visualization', '1', {packages: ['columnchart']});

function initMap() {
  // The following path marks a path from Mt. Whitney, the highest point in the
  // continental United States to Badwater, Death Valley, the lowest point.
  var path = [
      {lat: 36.579, lng: -118.292},  // Mt. Whitney
      {lat: 36.606, lng: -118.0638},  // Lone Pine
      {lat: 36.433, lng: -117.951},  // Owens Lake
      {lat: 36.588, lng: -116.943},  // Beatty Junction
      {lat: 36.34, lng: -117.468},  // Panama Mint Springs
      {lat: 36.24, lng: -116.832}];  // Badwater, Death Valley

  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 8,
    center: path[1],
    mapTypeId: 'terrain'
  });

  // Create an ElevationService.
  var elevator = new google.maps.ElevationService;

  // Draw the path, using the Visualization API and the Elevation service.
  displayPathElevation(path, elevator, map);
}

function displayPathElevation(path, elevator, map) {
  // Display a polyline of the elevation path.
  new google.maps.Polyline({
    path: path,
    strokeColor: '#0000CC',
    opacity: 0.4,
    map: map
  });

  // Create a PathElevationRequest object using this array.
  // Ask for 256 samples along that path.
  // Initiate the path request.
  elevator.getElevationAlongPath({
    'path': path,
    'samples': 256
  }, plotElevation);
}

// Takes an array of ElevationResult objects, draws the path on the map
// and plots the elevation profile on a Visualization API ColumnChart.
function plotElevation(elevations, status) {
  var chartDiv = document.getElementById('elevation_chart');
  if (status !== google.maps.ElevationStatus.OK) {
    // Show the error code inside the chartDiv.
    chartDiv.innerHTML = 'Cannot show elevation: request failed because ' +
        status;
    return;
  }
  // Create a new chart in the elevation_chart DIV.
  var chart = new google.visualization.ColumnChart(chartDiv);

  // Extract the data from which to populate the chart.
  // Because the samples are equidistant, the 'Sample'
  // column here does double duty as distance along the
  // X axis.
  var data = new google.visualization.DataTable();
  data.addColumn('string', 'Sample');
  data.addColumn('number', 'Elevation');
  for (var i = 0; i < elevations.length; i++) {
    data.addRow(['', elevations[i].elevation]);
  }

  // Draw the chart using the data within its DIV.
  chart.draw(data, {
    height: 150,
    legend: 'none',
    titleY: 'Elevation (m)'
  });
}

View example (elevation-paths.html).

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