C++ - 緯度和經度距離計算器

Question

我的程序計算以千米爲單位的兩點之間的距離，給出兩個緯度和經度值。

#include<iostream> 
#include <cmath> 

#define pi 3.14159265358979323846 

using namespace std; 

double calculateDistance(double lat1, double long1, double lat2, double long2) { 
    double dist; 
    dist = sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(long1 - long2); 
    dist = acos(dist); 
    dist = (6371 * pi * dist)/180; 
    return dist; 
} 

int main() { 
    cout << calculateDistance(51.752021, -1.257726, 51.507351, -0.127758); 
    return 0; 
} 

這就是我想實現的公式：

，我使用來測試我的輸出，http://www.movable-type.co.uk/scripts/latlong.html，其中列明瞭答案應該是82.60公里計算器。 （我越來越33.6227公里）

Answer 1

像這樣的東西應該工作（雖然沒有測試）：

double toRad(double degree) { 
    return degree/180 * pi; 
} 

double calculateDistance(double lat1, double long1, double lat2, double long2) { 
    double dist; 
    dist = sin(toRad(lat1)) * sin(toRad(lat2)) + cos(toRad(lat1)) * cos(toRad(lat2)) * cos(toRad(long1 - long2)); 
    dist = acos(dist); 
//  dist = (6371 * pi * dist)/180; 
    //got dist in radian, no need to change back to degree and convert to rad again. 
    dist = 6371 * dist; 
    return dist; 
}