Distorted lines in Travel Tracking in Flutter

Question

I am trying to implement a functionality, that if a user travels, then his/her live location will be captured in every interval of 10 sec. I am saving the captured lat-longs in local database and then run a API after every 10 mins to save data on server.

In every 10 secs I am calculating the distance between last last lat-long captured and updated lat-long captured.

When I tested it, I travelled around 35 KM, but total distance calculate was around 400 KM. On again testing, I travelled around 15 KM, but total distance calculate was around 150 KM.

Please anyone suggest what am I doing wrong. Or is there any alternative solution to track my path on which I travelled and total distance I covered.

For this I am using the below code to run the timer in every 10 secs

Timer.periodic(const Duration(seconds: 10), (timer) async {
  await CommonMethods.getCurrentLocationDateTime();
});

In every 10 secs, I run the below code:

static Future getCurrentLocationDateTime() async {
  _result = await Geolocator.getCurrentPosition(
    desiredAccuracy: LocationAccuracy.bestForNavigation,
  );
  if (_updatedLatitude == null && _updatedLongitude == null) {
    _previousLatitude = _result!.latitude;
    _previousLongitude = _result!.longitude;
  } else {
    _previousLatitude = _updatedLatitude;
    _previousLongitude = _updatedLongitude;
  }
  _updatedLatitude = _result!.latitude;
  _updatedLongitude = _result!.longitude;

  // Save data in a local variable
  Map<String, String> _currentLatLong = {
    "lat": _result!.latitude.toStringAsFixed(8),
    "long": _result!.longitude.toStringAsFixed(8),
  };
  CommonEntities.travelHistoryLatLng.add(_currentLatLong);

  // Update previous and current location names
  await placemarkFromCoordinates(_updatedLatitude!, _updatedLongitude!)
      .then((List<Placemark> placemarks) {
    _previousLocationName = (_currentLocationName == "")
        ? placemarks[0].name!
        : _currentLocationName;
    _currentLocationName = placemarks[0].subLocality!;
  }).catchError((e) {
    debugPrint(e.toString());
  });

  // Check if device is not moved for more than 2 hours
  // if not moved then stop the timer
  if (CommonEntities.travelHistoryLatLng.toSet().length == 1) {
    CommonEntities.idealStateTravelTimeSpent += 10;
    if (CommonEntities.idealStateTravelTimeSpent >= 7200) {
      CommonEntities.idealStateTravelTimeSpent = 0;
      // BackgroundLocation.stopLocationService();
      if (CommonEntities.travelTimer != null) {
        CommonEntities.travelTimer!.cancel();
      }
      CommonEntities.isTravelTimerActive = false;
      CommonEntities.workEndTime =
          CommonEntities.travelTrackingDetails["current_date_time"];
    }
  } else {
    CommonEntities.idealStateTravelTimeSpent = 0;
  }

  // Get Current date time of captured lat-longs
  _currentDateTime = DateTime.now();
  _currentDateTimeString = _currentDateTime.year.toString() +
      "-" +
      _currentDateTime.month.toString() +
      "-" +
      _currentDateTime.day.toString() +
      " " +
      _currentDateTime.hour.toString() +
      ":" +
      _currentDateTime.minute.toString();

  if (CommonEntities.workStartTime == "00:00") {
    CommonEntities.workStartTime = _currentDateTime.hour.toString() +
        ":" +
        _currentDateTime.minute.toString();
    // LocalSharedPreferences().setWorkStartTime();
  }

  // Update the total distance covered in 10 min
  updateDistanceTraveled();
  print("Total Distance Covered: " + CommonEntities.travelTrackingDetails["total_distance_covered"]);
  // Call API to save travel data in every 10 minutes.
  if (CommonEntities.totalTravelsecondsCount == 600) {
    // Calculate the time before 10 min and for time interval in post params
    String _currentTime = _currentDateTime.hour.toString() +
        ':' +
        _currentDateTime.minute.toString();
    DateTime _dateTimeBeforeTenMin =
        _currentDateTime.subtract(const Duration(minutes: 10));
    String _timeBeforeTenMin = _dateTimeBeforeTenMin.hour.toString() +
        ':' +
        _dateTimeBeforeTenMin.minute.toString();

    String _tempDistanceTravelled =
        CommonEntities.travelTrackingDetails["total_distance_covered"];
    CommonEntities.travelTrackingDetails["total_distance_covered"] = "";
    _distanceTravelled = 0.0;
    // Create post params value
    Map<String, dynamic> params = {
      'lat_long': jsonEncode(CommonEntities.travelHistoryLatLng),
      'date': _currentDateTime.day.toString() +
          '-' +
          _currentDateTime.month.toString() +
          '-' +
          _currentDateTime.year.toString() +
          ' ' +
          _currentDateTime.hour.toString() +
          ':' +
          _currentDateTime.minute.toString() +
          ':' +
          _currentDateTime.second.toString(),
      'distance_covered': _tempDistanceTravelled,
      'userID': await LocalSharedPreferences().getUserId(),
      'time_interval': _timeBeforeTenMin + '-' + _currentTime,
      'location_name': _currentLocationName,
      'status': 'progress',
    };

    // Call the API to save travel history of 10 min of server
    HomeProvider().saveTravelDetails(params);
    // await LocalSharedPreferences().saveTravelHistoryLatLng();

    // Reset the timer of 10 min, clear lat-long history of 10 min
    CommonEntities.totalTravelsecondsCount = 0;
    CommonEntities.travelHistoryLatLng = [];
  }
  CommonEntities.totalTravelsecondsCount += 10;

  // Save latlong and date time
  // BOC: commented logging of lat-long as the same is not required in final app
  // by shubham.bansal2
  AppLogs().logToFile(
      _result!.latitude.toString() + "-" + _result!.longitude.toString(),
      _currentDateTimeString);

  CommonEntities.travelTrackingDetails["updated_latitude"] =
      _updatedLatitude!.toStringAsFixed(8);
  CommonEntities.travelTrackingDetails["updated_longitude"] =
      _updatedLongitude!.toStringAsFixed(8);
  CommonEntities.travelTrackingDetails["updated_location_name"] =
      _currentLocationName;
  CommonEntities.travelTrackingDetails["previous_latitude"] =
      _previousLatitude!.toStringAsFixed(8);
  CommonEntities.travelTrackingDetails["previous_longitude"] =
      _previousLongitude!.toStringAsFixed(8);
  CommonEntities.travelTrackingDetails["previous_location_name"] =
      _previousLocationName;
  CommonEntities.travelTrackingDetails["total_distance_covered"] =
      _distanceTravelled.toStringAsFixed(8);
  CommonEntities.travelTrackingDetails["current_date_time"] =
      _currentDateTimeString;
}

Also for Distance, I am using the below code:

static updateDistanceTraveled() {
  var p = 0.017453292519943295;
  var c = cos;
  var a = 0.5 -
      c((_updatedLatitude! - _previousLatitude!) * p) / 2 +
      c(_previousLatitude! * p) *
          c(_updatedLatitude! * p) *
          (1 - c((_updatedLongitude! - _previousLongitude!) * p)) /
          2;
  _distanceTravelled = double.parse(CommonEntities.travelTrackingDetails["total_distance_covered"]);
  _distanceTravelled += (12742 * asin(sqrt(a))).toDouble();
  CommonEntities.travelTrackingDetails["total_distance_covered"] =
      _distanceTravelled.toStringAsFixed(5);
}