如何在unity 3d中获取GPS坐标

我得到了这个获取GPS坐标的代码，但不知何故，我只得到了相同坐标的输出。无论我走到哪里，它都不会改变输出，有时我的纬度为0，经度为0作为输出，请有人帮助我或有人有语法来获取坐标

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class testlocation : MonoBehaviour {
    public void Start()
    {
        // turn on location services, if available 
        Input.location.Start();
    }
    public void Update()
    {
        Text singleText = GameObject.Find("SinglePlayerButton").GetComponentInChildren<Text>();
        //Do nothing if location services are not available
        if (Input.location.isEnabledByUser)
        {
            float lat = Input.location.lastData.latitude;
            float lon = Input.location.lastData.longitude;

            singleText.text = "Depart lat: " + lat + "lon: " + lon;
        }
        else
            singleText.text = "gps off";
    }

}