Total distance calculation from LatLng List

Question

Im using dart/flutter and the 'package:latlong/latlong.dart' to parse a GPX file into a list of LatLng objects. That is working fine, but the next step is to find the total distance of the route.

The question here is

how can I get the total distance from a list of LatLng objects in Dart?

I have used Haversine formula before in Java, but not sure the best way to implement it using Dart. Any help of suggestion would be greatly appreciated.

Edit

Below is an attempt to get total distance based on the answer below. For some reason though it doesn't add to totalDistance and doesn't return a double.

The below is suppose to iterate through a list of 60+ LatLng objects and find distance between each one, adding to a totalDistance double which is returned at the end of the loop.

 static double getDistanceFromGPSPointsInRoute(List<LatLng> gpsList) {     double totalDistance = 0.0;      for (var i = 0; i < gpsList.length; i++) {       var p = 0.017453292519943295;       var c = cos;       var a = 0.5 -           c((gpsList[i + 1].latitude - gpsList[i].latitude) * p) / 2 +           c(gpsList[i].latitude * p) *               c(gpsList[i + 1].latitude * p) *               (1 - c((gpsList[i + 1].longitude - gpsList[i].longitude) * p)) /               2;       double distance = 12742 * asin(sqrt(a));       totalDistance += distance;       print('Distance is ${12742 * asin(sqrt(a))}');     }     print('Total distance is $totalDistance');     return totalDistance;   } 

Output

flutter: Distance is 0.004143962775784678 flutter: Distance is 0.0041439635323316775 flutter: Distance is 0.007796918986828574 flutter: Distance is 0.007285385943437824 flutter: Distance is 0.006890844300938902 flutter: Distance is 0.006353952460010352 flutter: Distance is 0.005560051252981138 

As you can see above, there is no mention of Total Distance.

Example of LatLng List

flutter: -36.84975 , 174.646685 flutter: -36.849692 , 174.646497 flutter: -36.84967 , 174.646436 flutter: -36.849578 , 174.646264 flutter: -36.849502 , 174.646164 flutter: -36.849367 , 174.646038 flutter: -36.849209 , 174.645959 flutter: -36.849155 , 174.64594 flutter: -36.849107 , 174.645932 flutter: -36.849058 , 174.645922 flutter: -36.848952 , 174.645895 flutter: -36.84886 , 174.645906 flutter: -36.84879 , 174.645913 flutter: -36.848748 , 174.645836 flutter: -36.848744 , 174.645802 

Answer 1

Try this please. I tested it with Google Maps and works accurately. You can do a loop and find total distance by using 2 points each time. I added some random dummy data to show how it works. Copy this code to https://dartpad.dartlang.org/ and test easily.

import 'dart:math' show cos, sqrt, asin;  void main() {   double calculateDistance(lat1, lon1, lat2, lon2){     var p = 0.017453292519943295;     var c = cos;     var a = 0.5 - c((lat2 - lat1) * p)/2 +            c(lat1 * p) * c(lat2 * p) *            (1 - c((lon2 - lon1) * p))/2;     return 12742 * asin(sqrt(a));   }    List<dynamic> data = [     {       "lat": 44.968046,       "lng": -94.420307     },{       "lat": 44.33328,       "lng": -89.132008     },{       "lat": 33.755787,       "lng": -116.359998     },{       "lat": 33.844843,       "lng": -116.54911     },{       "lat": 44.92057,       "lng": -93.44786     },{       "lat": 44.240309,       "lng": -91.493619     },{       "lat": 44.968041,       "lng": -94.419696     },{       "lat": 44.333304,       "lng": -89.132027     },{       "lat": 33.755783,       "lng": -116.360066     },{       "lat": 33.844847,       "lng": -116.549069     },   ];   double totalDistance = 0;   for(var i = 0; i < data.length-1; i++){     totalDistance += calculateDistance(data[i]["lat"], data[i]["lng"], data[i+1]["lat"], data[i+1]["lng"]);   }   print(totalDistance); }