以上で完了です。

開発を始めるには、デベロッパー ドキュメント をご覧下さい。

Google Maps JavaScript API をアクティベートする

まず初めに Google Developers Console で次の作業を行います。

  1. プロジェクトを作成または選択する
  2. Google Maps JavaScript API と関連サービスをアクティベートする
  3. 適切なキーを作成する
続ける

Navigation functions (heading)

This example demonstrates computing the heading between two coordinates using the Geometry library. Drag the markers on the map to see the origin, destination and heading change accordingly.

Read the documentation or view this example full screen.

// This example requires the Geometry library. Include the libraries=geometry
// parameter when you first load the API. For example:
// <script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=geometry">

var marker1, marker2;
var poly, geodesicPoly;

function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 4,
    center: {lat: 34, lng: -40.605}
  });

  map.controls[google.maps.ControlPosition.TOP_CENTER].push(
      document.getElementById('info'));

  marker1 = new google.maps.Marker({
    map: map,
    draggable: true,
    position: {lat: 40.714, lng: -74.006}
  });

  marker2 = new google.maps.Marker({
    map: map,
    draggable: true,
    position: {lat: 48.857, lng: 2.352}
  });

  var bounds = new google.maps.LatLngBounds(
      marker1.getPosition(), marker2.getPosition());
  map.fitBounds(bounds);

  google.maps.event.addListener(marker1, 'position_changed', update);
  google.maps.event.addListener(marker2, 'position_changed', update);

  poly = new google.maps.Polyline({
    strokeColor: '#FF0000',
    strokeOpacity: 1.0,
    strokeWeight: 3,
    map: map,
  });

  geodesicPoly = new google.maps.Polyline({
    strokeColor: '#CC0099',
    strokeOpacity: 1.0,
    strokeWeight: 3,
    geodesic: true,
    map: map
  });

  update();
}

function update() {
  var path = [marker1.getPosition(), marker2.getPosition()];
  poly.setPath(path);
  geodesicPoly.setPath(path);
  var heading = google.maps.geometry.spherical.computeHeading(path[0], path[1]);
  document.getElementById('heading').value = heading;
  document.getElementById('origin').value = path[0].toString();
  document.getElementById('destination').value = path[1].toString();
}
<div id="map"></div>
<div id="floating-panel">
  Origin: <input type="text" readonly id="origin">
  Destination: <input type="text" readonly id="destination"><br>
  Heading: <input type="text" readonly id="heading"> degrees
</div>
/* Always set the map height explicitly to define the size of the div
 * element that contains the map. */
#map {
  height: 100%;
}
/* Optional: Makes the sample page fill the window. */
html, body {
  height: 100%;
  margin: 0;
  padding: 0;
}
#floating-panel {
  position: absolute;
  top: 10px;
  left: 25%;
  z-index: 5;
  background-color: #fff;
  padding: 5px;
  border: 1px solid #999;
  text-align: center;
  font-family: 'Roboto','sans-serif';
  line-height: 30px;
  padding-left: 10px;
}
<!-- Replace the value of the key parameter with your own API key. -->
<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk&libraries=geometry&callback=initMap"
        async defer></script>

実際に試す

コードブロックの右上にカーソルを合わせて、コードをコピーするか、コードを JSFiddl で開きます。

<!DOCTYPE html>
<html>
  <head>
    <title>Navigation functions (heading)</title>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no">
    <meta charset="utf-8">
    <style>
      /* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
      #map {
        height: 100%;
      }
      /* Optional: Makes the sample page fill the window. */
      html, body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
      #floating-panel {
        position: absolute;
        top: 10px;
        left: 25%;
        z-index: 5;
        background-color: #fff;
        padding: 5px;
        border: 1px solid #999;
        text-align: center;
        font-family: 'Roboto','sans-serif';
        line-height: 30px;
        padding-left: 10px;
      }
    </style>
  </head>
  <body>
    <div id="map"></div>
    <div id="floating-panel">
      Origin: <input type="text" readonly id="origin">
      Destination: <input type="text" readonly id="destination"><br>
      Heading: <input type="text" readonly id="heading"> degrees
    </div>
    <script>
      // This example requires the Geometry library. Include the libraries=geometry
      // parameter when you first load the API. For example:
      // <script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=geometry">

      var marker1, marker2;
      var poly, geodesicPoly;

      function initMap() {
        var map = new google.maps.Map(document.getElementById('map'), {
          zoom: 4,
          center: {lat: 34, lng: -40.605}
        });

        map.controls[google.maps.ControlPosition.TOP_CENTER].push(
            document.getElementById('info'));

        marker1 = new google.maps.Marker({
          map: map,
          draggable: true,
          position: {lat: 40.714, lng: -74.006}
        });

        marker2 = new google.maps.Marker({
          map: map,
          draggable: true,
          position: {lat: 48.857, lng: 2.352}
        });

        var bounds = new google.maps.LatLngBounds(
            marker1.getPosition(), marker2.getPosition());
        map.fitBounds(bounds);

        google.maps.event.addListener(marker1, 'position_changed', update);
        google.maps.event.addListener(marker2, 'position_changed', update);

        poly = new google.maps.Polyline({
          strokeColor: '#FF0000',
          strokeOpacity: 1.0,
          strokeWeight: 3,
          map: map,
        });

        geodesicPoly = new google.maps.Polyline({
          strokeColor: '#CC0099',
          strokeOpacity: 1.0,
          strokeWeight: 3,
          geodesic: true,
          map: map
        });

        update();
      }

      function update() {
        var path = [marker1.getPosition(), marker2.getPosition()];
        poly.setPath(path);
        geodesicPoly.setPath(path);
        var heading = google.maps.geometry.spherical.computeHeading(path[0], path[1]);
        document.getElementById('heading').value = heading;
        document.getElementById('origin').value = path[0].toString();
        document.getElementById('destination').value = path[1].toString();
      }
    </script>
    <script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=geometry&callback=initMap"
        async defer></script>
  </body>
</html>

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Google Maps JavaScript API
Google Maps JavaScript API
ご不明な点がありましたら、Google のサポートページをご覧ください。