Developer's Guide

The Google Maps Elevation API provides 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 elevation changes along routes.

This document is intended for website and mobile developers who want to use elevation data within maps provided by one of the Google Maps APIs. It provides an introduction to using the API and reference material on the available parameters.

Introduction

The Google Maps Elevation API provides elevation data for all 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.

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

You access the Google Maps Elevation API through an HTTP interface. Users of the Google Maps JavaScript API may also access this API directly by using the ElevationService() object. (See Elevation Service for more information.)

Before you start developing with the Elevation API, review the authentication requirements (you need an API key) and the API usage limits.

Elevation Requests

Google Maps Elevation API requests are constructed as a URL string. The API returns elevation data for locations on the earth. You specify location data in one of two ways:

• As a set of one or more locations.
• As a series of connected points along a path.

Either of these approachs uses latitude/longitude coordinates to identify the locations or path vertices. This document describes the required format of Google Maps Elevation API URLs and the available parameters.

The Google Maps Elevation API returns data for single point queries of the highest accuracy possible. Batch queries involving multiple locations may return data with less accuracy, especially if the locations are spread apart, as some smoothing of data occurs.

A Google Maps Elevation API request takes the following form:

https://maps.googleapis.com/maps/api/elevation/outputFormat?parameters

where outputFormat may be either of the following values:

• json (recommended), indicates output in JavaScript Object Notation (JSON); or
• xml, indicates output in XML, wrapped within a <ElevationResponse> node.

Note: URLs must be properly encoded to be valid and are limited to 2048 characters for all web services. Be aware of this limit when constructing your URLs. Note that different browsers, proxies, and servers may have different URL character limits as well.

HTTPS or HTTP

Security is important and HTTPS is recommended whenever possible, especially for applications that include sensitive user data, such as a user's location, in requests. Using HTTPS encryption makes your application more secure, and more resistant to snooping or tampering.

If HTTPS is not possible, to access the Google Maps Elevation API over HTTP, use:

http://maps.googleapis.com/maps/api/elevation/outputFormat?parameters

Request Parameters

Requests to the Google Maps Elevation API utilize different parameters based on whether the request is for discrete locations or for an ordered path. For discrete locations, requests for elevation return data on the specific locations passed in the request; for paths, elevation requests are instead sampled along the given path.

As is standard in all URLs, parameters are separated using the ampersand (&) character. The list of parameters and their possible values are denoted below.

All Requests

• key — (required) Your application's API key. This key identifies your application for purposes of quota management. Learn how to get a key.

  Note: Google Maps APIs Premium Plan customers may use either an API key, or a valid client ID and digital signature, in your Elevation requests. Get more information on authentication parameters for Premium Plan customers.

Positional Requests

• locations (required) defines the location(s) on the earth from which to return elevation data. This parameter takes either a single location as a comma-separated {latitude,longitude} pair (e.g. "40.714728,-73.998672") or multiple latitude/longitude pairs passed as an array or as an encoded polyline. For more information, see Specifying Locations below.

Sampled Path Requests

• path (required) defines a path on the earth for which to return elevation data. This parameter defines a set of two or more ordered {latitude,longitude} pairs defining a path along the surface of the earth. This parameter must be used in conjunction with the samples parameter described below. For more information, see Specifying Paths below.
• 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.

Specifying Locations

Positional requests are indicated through use of the locations parameter, indicating elevation requests for the specific locations passed as latitude/longitude values.

The locations parameter may take the following arguments:

• A single coordinate: locations=40.714728,-73.998672
• An array of coordinates separated using the pipe ('|') character: locations=40.714728,-73.998672|-34.397,150.644
• A set of encoded coordinates using the Encoded Polyline Algorithm: locations=enc:gfo}EtohhU

Latitude and longitude coordinate strings are defined using numerals within a comma-separated text string. For example, "40.714728,-73.998672" is a valid locations value. Latitude and longitude values must correspond to a valid location on the face of the earth. Latitudes can take any value between -90 and 90 while longitude values can take any value between -180 and 180. If you specify an invalid latitude or longitude value, your request will be rejected as a bad request.

You may pass any number of multiple coordinates within an array or encoded polyline, as long as you don't exceed the service quotas, while still constructing a valid URL. 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.

Specifying Paths

Sampled path requests are indicated through use of the path and samples parameters, indicating a request for elevation data along a path at specified intervals. As with positional requests using the locations parameter, 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 only at the vertices, path requests are sampled along the length of the path, based on the number of samples specified (inclusive of the endpoints).

The path parameter may take either of the following arguments:

• An array of two or more comma-separated coordinate text strings separated using the pipe ('|') character: path=40.714728,-73.998672|-34.397,150.644
• Encoded coordinates using the Encoded Polyline Algorithm: path=enc:gfo}EtohhUxD@bAxJmGF

Latitude and longitude coordinate strings are defined using numerals within a comma-separated text string. For example, "40.714728,-73.998672|-34.397, 150.644" is a valid path value. Latitude and longitude values must correspond to a valid location on the face of the earth. Latitudes can take any value between -90 and 90 while longitude values can take any value between -180 and 180. If you specify an invalid latitude or longitude value, your request will be rejected as a bad request.

You may pass any number of multiple coordinates within an array or encoded polyline, as long as you don't exceed the service quotas, while still constructing a valid URL. 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.

Elevation Responses

For each valid request, the Elevation service will return an Elevation response in the format indicated within the request URL. Each response will contain the following elements:

An Elevation status code, which may be one of the following:

• OK indicating the API request was successful.
• INVALID_REQUEST indicating the API request was malformed.
• OVER_QUERY_LIMIT indicating the requestor has exceeded quota.
• REQUEST_DENIED indicating the API did not complete the request.
• UNKNOWN_ERROR indicating an unknown error.

When the status code is other than OK, there may be an additional error_message field within the Elevation response object. This field contains more detailed information about the reasons behind the given status code.

Note: This field is not guaranteed to be always present, and its content is subject to change.

An array of results containing the following elements:

• A location element (containing lat and lng elements) 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.

Positional Elevation Examples

The following example requests the elevation for Denver, Colorado, the "Mile High City" in the JSON format:

https://maps.googleapis.com/maps/api/elevation/json?locations=39.7391536,-104.9847034&key=YOUR_API_KEY

{
   "results" : [
      {
         "elevation" : 1608.637939453125,
         "location" : {
            "lat" : 39.73915360,
            "lng" : -104.98470340
         },
         "resolution" : 4.771975994110107
      }
   ],
   "status" : "OK"
}

The following example shows multiple responses (for Denver, CO and for Death Valley, CA).

This request demonstrates using the JSON output flag:

https://maps.googleapis.com/maps/api/elevation/json?locations=39.7391536,-104.9847034|36.455556,-116.866667&key=YOUR_API_KEY

This request demonstrates using the XML output flag:

https://maps.googleapis.com/maps/api/elevation/xml?locations=39.7391536,-104.9847034|36.455556,-116.866667&key=YOUR_API_KEY

Click the tabs below to see the sample JSON and XML responses.

{
   "results" : [
      {
         "elevation" : 1608.637939453125,
         "location" : {
            "lat" : 39.73915360,
            "lng" : -104.98470340
         },
         "resolution" : 4.771975994110107
      },
      {
         "elevation" : -50.78903579711914,
         "location" : {
            "lat" : 36.4555560,
            "lng" : -116.8666670
         },
         "resolution" : 19.08790397644043
      }
   ],
   "status" : "OK"
}

<?xml version="1.0" encoding="UTF-8"?>
<ElevationResponse>
 <status>OK</status>
 <result>
  <location>
   <lat>39.7391536</lat>
   <lng>-104.9847034</lng>
  </location>
  <elevation>1608.6379395</elevation>
  <resolution>4.7719760</resolution>
 </result>
 <result>
  <location>
   <lat>36.4555560</lat>
   <lng>-116.8666670</lng>
  </location>
  <elevation>-50.7890358</elevation>
  <resolution>19.0879040</resolution>
 </result>
</ElevationResponse>

The following examples requests elevation data along a straight line path from Mt. Whitney, CA to Badwater, CA, the highest and lowest points in the continental United States. We ask for three samples, so that will include the two endpoints and the halfway point.

https://maps.googleapis.com/maps/api/elevation/json?path=36.578581,-118.291994|36.23998,-116.83171&samples=3&key=YOUR_API_KEY

{
   "results" : [
      {
         "elevation" : 4411.941894531250,
         "location" : {
            "lat" : 36.5785810,
            "lng" : -118.2919940
         },
         "resolution" : 19.08790397644043
      },
      {
         "elevation" : 1381.861694335938,
         "location" : {
            "lat" : 36.41150289067028,
            "lng" : -117.5602607523847
         },
         "resolution" : 19.08790397644043
      },
      {
         "elevation" : -84.61699676513672,
         "location" : {
            "lat" : 36.239980,
            "lng" : -116.831710
         },
         "resolution" : 19.08790397644043
      }
   ],
   "status" : "OK"
}

Creating Elevation Charts

Elevation data must be used in conjunction with a display of data on a Google Map. The Chart API ( https://code.google.com/apis/chart/) is well-suited to creating elevation charts which you can display alongside your maps.

The following Python example calculates elevation data between Mt. Whitney and Badwater, Death Valley and uses those values to create en elevation chart:

import simplejson
import urllib

ELEVATION_BASE_URL = 'https://maps.googleapis.com/maps/api/elevation/json'
CHART_BASE_URL = 'http://chart.apis.google.com/chart'

def getChart(chartData, chartDataScaling="-500,5000", chartType="lc",chartLabel="Elevation in Meters",chartSize="500x160",chartColor="orange", **chart_args):
    chart_args.update({
      'cht': chartType,
      'chs': chartSize,
      'chl': chartLabel,
      'chco': chartColor,
      'chds': chartDataScaling,
      'chxt': 'x,y',
      'chxr': '1,-500,5000'
    })

    dataString = 't:' + ','.join(str(x) for x in chartData)
    chart_args['chd'] = dataString.strip(',')

    chartUrl = CHART_BASE_URL + '?' + urllib.urlencode(chart_args)

    print chartUrl

    def getElevation(path="36.578581,-118.291994|36.23998,-116.83171",samples="100", **elvtn_args):
      elvtn_args.update({
        'path': path,
        'samples': samples
      })

      url = ELEVATION_BASE_URL + '?' + urllib.urlencode(elvtn_args)
      response = simplejson.load(urllib.urlopen(url))

      # Create a dictionary for each results[] object
      elevationArray = []

      for resultset in response['results']:
        elevationArray.append(resultset['elevation'])

      # Create the chart passing the array of elevation data
      getChart(chartData=elevationArray)

if __name__ == '__main__':
    # Mt. Whitney
    startStr = "36.578581,-118.291994"
    # Death Valley
    endStr = "36.23998,-116.83171"

    pathStr = startStr + "|" + endStr

    getElevation(pathStr)

The following images show how this information might be displayed on a map and/or chart:

Download the ElevationChartCreator.py code from js-v2-samples.

The sensor Parameter

The Google Maps API previously required that you include the sensor parameter to indicate whether your application used a sensor to determine the user's location. This parameter is no longer required.