从 LatLng 列表计算总距离 [英] Total distance calculation from LatLng List

问题描述

我使用 dart/flutter 和 'package:latlong/latlong.dart' 将 GPX 文件解析为 LatLng 对象列表.这工作正常，但下一步是找到路线的总距离.

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.

这里的问题是

如何从 LatLng 对象列表中获取总距离飞镖?

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

我之前在 Java 中使用过 Haversine 公式，但不确定使用 Dart 实现它的最佳方法.任何建议的帮助将不胜感激.

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.

编辑

下面是根据下面的答案尝试获得总距离的尝试.出于某种原因，虽然它不会添加到 totalDistance 并且不会返回双精度值.

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.

下面假设遍历一个包含 60 多个 LatLng 对象的列表，并找到每个对象之间的距离，并添加到循环结束时返回的 totalDistance 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;
  }

输出

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

正如你在上面看到的，没有提到总距离.

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

纬度列表示例

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

推荐答案

请试试这个.我用谷歌地图对其进行了测试，并且工作准确.您可以进行循环并每次使用 2 个点来计算总距离.我添加了一些随机虚拟数据来展示它是如何工作的.将此代码复制到 https://dartpad.dartlang.org/ 并轻松测试.

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);
}

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