distanceBetween() returns inaccurate result?

Question

I use distanceBetween() of Location class to calculate the distance between two points as follows:

private float getDistanceInMiles(GeoPoint p1, GeoPoint p2) {

    double lat1 = ((double)p1.getLatitudeE6()) / 1e6;
    double lng1 = ((double)p1.getLongitudeE6()) / 1e6;
    double lat2 = ((double)p2.getLatitudeE6()) / 1e6;
    double lng2 = ((double)p2.getLongitudeE6()) / 1e6;
    float [] dist = new float[1];
    Log.i("destination coordinates", "Latitude:" + lat2 + ", Longitude: " + lng2);
        Location.distanceBetween(lat1, lng1, lat2, lng2, dist);

    return dist[0] * 0.000621371192f;
}

Documentation says that distanceBetween() "Computes the approximate distance in meters between two locations, and optionally the initial and final bearings of the shortest path between them." However the difference between the result returned by distanceBetween() and real GPS device or Google Navigation app is pretty big. For example my method will return 6.2 miles while google maps shows 10 miles for the same location. I double check the coordinates of the starting point p1 and ending point p2 and they seems to be correct. Is that how distanceBetween() method works or Am I doing something wrong? And by the way Is there a way to use Google Place API to retrieve a distance as a JSON response?

Distance calculated by Google Maps: 6.1 miles

enter image description here

And the result of

Location.distanceBetween(41.742964, -87.995971, 41.811511, -87.967923, dist) is

4.947700

Android MapView does not use the Google Maps API V3. (tag removed) — Marcelo, Jan 31 '13 at 07:35
Marcin S., 41.742964 is not the same as 41.742972, and -87.995971 is not the same as -87.996068 either... — Jorge, Jan 08 '14 at 20:38

score 14 · Answer 1 · answered Jan 31 '13 at 03:50

14

Google Navigation generally reports driving or walking distance along the set of steps in the directions list, not straight-line distance, which is what distanceBetween() reports.

answered Jan 31 '13 at 03:50

CommonsWare

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oh ok. So this is a straight-line distance. How could I retrieve the distance calculated by google app? Google Place Api seems to not include the distance in a JSON response. Thank you for the answer. – Marcin S. Jan 31 '13 at 03:58
@MarcinS.: "How could I retrieve the distance calculated by google app?" -- there is no API for that in Android. Whether there is some Google Web service API for it or not, I have no idea. – CommonsWare Jan 31 '13 at 04:01
I found something like this https://developers.google.com/places/documentation/search It's probably unofficial. Thanks. – Marcin S. Jan 31 '13 at 04:02
@CommonsWare, just tested the Location.distanceBetween() against LFLL's (r17) calculation and it's 3041m vs. 3032m --> 0.3% difference. The location was accross a city. Both calculations finished in 0 ms. – Saran Sep 11 '14 at 15:22

Marcin S. · Accepted Answer · 2013-01-31T16:35:01.973

To get a distance from a Google Maps I have used Google Directions API and JSON parser to retrieve the distance value:

private double getDistanceInfo(double lat1, double lng1, String destinationAddress) {
            StringBuilder stringBuilder = new StringBuilder();
            Double dist = 0.0;
            try {

            destinationAddress = destinationAddress.replaceAll(" ","%20");    
            String url = "http://maps.googleapis.com/maps/api/directions/json?origin=" + lat1 + "," + lng1 + "&destination=" + destinationAddress + "&mode=driving&sensor=false";

            HttpPost httppost = new HttpPost(url);

            HttpClient client = new DefaultHttpClient();
            HttpResponse response;
            stringBuilder = new StringBuilder();


                response = client.execute(httppost);
                HttpEntity entity = response.getEntity();
                InputStream stream = entity.getContent();
                int b;
                while ((b = stream.read()) != -1) {
                    stringBuilder.append((char) b);
                }
            } catch (ClientProtocolException e) {
            } catch (IOException e) {
            }

            JSONObject jsonObject = new JSONObject();
            try {

                jsonObject = new JSONObject(stringBuilder.toString());

                JSONArray array = jsonObject.getJSONArray("routes");

                JSONObject routes = array.getJSONObject(0);

                JSONArray legs = routes.getJSONArray("legs");

                JSONObject steps = legs.getJSONObject(0);

                JSONObject distance = steps.getJSONObject("distance");

                Log.i("Distance", distance.toString());
                dist = Double.parseDouble(distance.getString("text").replaceAll("[^\\.0123456789]","") );

            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            return dist;
        }

That's because you're calling this method on the main UI Thread. You **must** call this method in another Thread or in an AsyncTask — Jason John, Aug 15 '14 at 18:27

distanceBetween() returns inaccurate result?

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