如何从谷歌地图方向API获取经度和纬度数组

Question

I am creating Tracking software. Android device is sending its location and now I have to check if that location is within that direction set by the admin.

Basically, admin set a route for an employee (employee is using an android phone) using google maps (could be saved as series of latitude and longitude in database ), if location sent by an employee (latitude , longitude) is not in his route then admin will get a notification on website. I want help with camparison. Simply i want to know if employee is deviated from its route or not . Is it possible to do it? Please do answer I will be very grateful.

<script>
  function initMap() {
    var directionsService = new google.maps.DirectionsService;
    var directionsDisplay = new google.maps.DirectionsRenderer;
    var map = new google.maps.Map(document.getElementById('map'), {
      zoom: 7,
      center: {lat: 41.85, lng: -87.65}
    });
    directionsDisplay.setMap(map);

    var onChangeHandler = function() {
      calculateAndDisplayRoute(directionsService, directionsDisplay);
    };
    document.getElementById('start').addEventListener('change', onChangeHandler);
    document.getElementById('end').addEventListener('change', onChangeHandler);
  }

  function calculateAndDisplayRoute(directionsService, directionsDisplay) {
    directionsService.route({
      origin: document.getElementById('start').value,
      destination: document.getElementById('end').value,
      travelMode: 'DRIVING'
    }, function(response, status) {
      if (status === 'OK') {
          console.log(response);
        directionsDisplay.setDirections(response);
      } else {
        window.alert('Directions request failed due to ' + status);
      }
    });
  }
</script>

Can I extract array of latitude and longitude from variable response? If there is better way please share.

Answer 1

Your question is quite broad and therefore my answer will be broad too but that would be too much to write in a comment...

A route returned by the Directions service is not a collection of points or coordinates. It's a collection of legs and steps, with a start and end point (and an encrypted Polyline). See here for details .

As a side note, encoded Polylines can be decoded too, see here for more info.

Coordinates you might get from the employee devices might not be 100% accurate and thus might not fall exactly on the directions path. So you will need some tolerance calculation.

You might want to check the Roads API and more specifically the Snap to roads and/or Nearest services.

Alternatively, the Geometry library (which you need to load with your API call) also has a method called isLocationOnEdge which you can use to determine whether a point falls on or near a Polyline, based on a custom degree tolerance.

Hope this helps you get started!