def haversine(lat1,lon1,lat2,lon2): # 經度1，緯度1，經度2，緯度2 （十進制度數）

    """

    Calculate the great circle distance between two points

    on the earth (specified in decimal degrees)

    """

 

    # 將十進制度數轉化為弧度

    lon1, lat1, lon2, lat2 = map(math.radians, [lon1, lat1, lon2, lat2])  

 

    # haversine公式

    dlon = lon2 - lon1

    dlat = lat2 - lat1

    a = math.sin(dlat/2)**2 + math.cos(lat1) * math.cos(lat2) * math.sin(dlon/2)**2

    c = 2 * math.asin(math.sqrt(a))

    r = 6371 # 地球平均半徑，單位為公里

    return c * r