Android的GPS定位速度不可靠 [英] Android GPS Location Speed Unreliable

问题描述

写一个GPS记录应用程序〜

我发现关于位置报道<$ C $由 getSpeed​​（）方法的返回值C> LocationManager 有大量不可靠的。我使用 LocationManager.GPS_PROVIDER ，过滤通过 onLocationChanged 以获得最佳的精度提供的位置。即使在个位数的精度水平恢复速度一般高的离谱。我们谈论最多200 MP /小时（是的，我知道这是记录在米/秒）的时候，手机是静止的。

我测试两种不同型号的Andr​​oid手机一样code基，运行两个不同的操作系统版本，并看到了同样的问题，所以我希望这是一个code问题。

我在想什么？我已经试过了一个时间窗口平均位置，但没有成功。我是不是有根据距离制定出自己的速度值行驶/时间？这将是令人失望的。

正如你所看到的，我没有做什么特别的东西 - 一个小的过滤精度，即使这两个 AverageSpeed​​ 和 _bestLocation.getSpeed （）定期unfeasibly高，即使在定位精度还是不错的。

 公共无效onLocationChanged（位置定位）{
    如果（location.getAccuracy（）＆其中; 25F）{
        _recentLocations.add（位置）;

        如果（_bestLocation == NULL || location.getAccuracy（）＆LT; = _bestLocation.getAccuracy（））
            _bestLocation =位置;
    }

    如果（（_bestLocation = NULL和放大器;！＆安培; _bestLocation.getAccuracy（）＆LT; 10F和放大器;＆安培; _recentLocations.size（）＆GT; = 10）
            || _recentLocations.size（）＆GT; = 25）
    {
        诠释计数= 0;
            浮TotalSpeed​​ = 0F;
            浮AverageSpeed​​ = 0F;
            的for（int i = 0; I＆LT; _recentLocations.size（）;我++）{
                如果（_recentLocations.get（ⅰ）.hasSpeed​​（））{
                    伯爵++;
                    TotalSpeed​​ + = _recentLocations.get（ⅰ）.getSpeed​​（）;
                }
            }

        如果（计数大于0）
                AverageSpeed​​ = TotalSpeed​​ /计数;
        }
}
 

解决方案

因为更多的则7年来我对GPS硬件工作过。精度读数也并非100％准确。 厂家说明准确性以及用于测量它的系统。 CEP，RMS，2DRMS，和R95是一些系统。 阅读这篇文章的详细信息： http://en.wikipedia.org/wiki/Circular_error_probable

精度数字不包括异常值。例如，如果规定的精度5米然后在良好信号条件下拍摄的读数将具有5米，95％的时间最大误差。没有什么可以说对剩下的5％的读数。防止这些 异常值是特制的酱汁，使一个良好的基于​​位置的应用程序从休息站出来。

有些事情你可以做的是：

1. 筛选出疯狂的高速度。利用高度作为提示用于在飞机之中。
2. 从运动传感器的信息关联起来，并看看他们是否认同 全球定位系统。运动传感器特征将处于稳定状态非常不同 而在运动。
3. 在GSM / 3G小区的典型尺寸是下在城市一公里 地区和人口稀少地区5-10公里。如果 车辆正在高速移动时的一段时间和小区发射塔 信息仍然是一样的，你知道什么是错的。
4. 是否需要GPS定位阅读北部一个时刻和南部的下一个太 高速？如果是的话，它很可能是全球定位系统错误。
5. 检查GPS caluclation使用的卫星数量。 12表现突出，9是健康的，5个或更少的差，4为最低限度的纬度，经度+高度 计算，3是最低限度的纬度，经度计算。点儿小于3不是有效的读数。你可以更自信数据的有效性，如果staellites数是很高的。

Writing a GPS logging application~

I'm finding the values returned by the getSpeed() method on Locations reported by LocationManager are massively unreliable. I'm using LocationManager.GPS_PROVIDER, filtering the Locations provided through onLocationChanged for best accuracy. Even at single digit accuracy levels the speed returned is generally ridiculously high. We're talking up to 200 mp/h (yes I know it's logged in metres/sec) when the phone is stationary.

I'm testing the same code base on two different model Android phones, running two different OS versions, and seeing the same issues so I expect this is a code issue.

What am I missing? I've tried averaging locations over a window of time, to no avail. Am I going to have to work out my own speed values based on distance travelled / time? This would be disappointing.

As you will see, I'm not doing anything special - a little filtering for accuracy, even after this both AverageSpeed and _bestLocation.getSpeed() are regularly unfeasibly high, even when accuracy of the location is good.

public void onLocationChanged(Location location) {
    if (location.getAccuracy() < 25f) {
        _recentLocations.add(location);

        if (_bestLocation == null || location.getAccuracy() <= _bestLocation.getAccuracy())
            _bestLocation = location;
    }

    if ((_bestLocation != null && _bestLocation.getAccuracy() < 10f && _recentLocations.size() >= 10)
            || _recentLocations.size() >= 25)
    {
        int Count = 0;
            float TotalSpeed = 0f;
            float AverageSpeed = 0f;
            for (int i = 0; i<_recentLocations.size(); i++) {
                if (_recentLocations.get(i).hasSpeed()) {
                    Count++;
                    TotalSpeed += _recentLocations.get(i).getSpeed();
                }
            }

        if (Count > 0)
                AverageSpeed = TotalSpeed / Count;
        }
}

解决方案

I have worked on GPS hardware since more then 7 years now. The accuracy reading is also not 100% accurate. Manufacturers state accuracy along with the system used for measuring it. CEP, RMS, 2DRMS, and R95 are some of the systems. Read this article for more information: http://en.wikipedia.org/wiki/Circular_error_probable

The accuracy figure does not include outliers. For example, if stated accuracy 5 meters then readings taken in good signal conditions will have maximum error of 5 meters, 95% of the time. Nothing can be said about the remaining 5% readings. Protection against these outliers is the special sauce that makes a good location based app stand out from the rest.

Some things you can do are:

1. Filter out insanely high speeds. Make use of altitude as hint for being in a airplane.
2. Correlate information from motion sensors and see if they agree with GPS. Motion sensor signatures will be very different in steady state and in motion.
3. The typical size of a GSM/3G cell is under a kilometer in urban areas and 5-10 kilometers in sparsely populated areas. If the vehicle is moving at high speed for some time and the cell tower information is still the same, you know something is wrong.
4. Does the GPS fix read north one moment and south the next that too at a high speed? If yes, it is most likely a GPS error.
5. Check the number of Satellites used in GPS caluclation. 12 is outstanding, 9 is healthy, 5 or less is poor, 4 is bare minimum for lat,lon + altitude calculation, 3 is bare minimum for lat,lon calculation. Anyting less than 3 is not a valid reading. You can be much more confident about the validity of data if number of staellites is high.

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