我开发一个应用程序，它更是你的朋友之间的时移赛车。

I am developing an app which is more of a time-shift racing between your friends.

我需要计算行驶中的车辆的速度，我不想使用 Location.getSpeed​​（）方法。 （详细解释在底部为什么我不希望使用它）

I need to calculate speed of a moving vehicle, and I don't want to use Location.getSpeed() method. (Explained in detail in the bottom why I don't want to use it)

我试图计算速度与纬度和经度提供给我的帮助，而这正是我需要帮助。

I am trying to calculate speed with the help of Latitude and Longitude available to me, and this is where I need help.

帮助需要的：我想知道的是：

我使用下面的code：

I am using the following code:

这给了我两个经纬度点之间的距离：

long getDistanceBetweenPoints(double lat1, double lng1, double lat2, double lng2 ){
        double dLat = Math.toRadians(lat2 - lat1);
        double dLon = Math.toRadians(lng2 - lng1);
        double a = Math.sin(dLat / 2) * Math.sin(dLat / 2)
                + Math.cos(Math.toRadians(lat1))
                * Math.cos(Math.toRadians(lat2)) * Math.sin(dLon / 2)
                * Math.sin(dLon / 2);
        double c = 2 * Math.asin(Math.sqrt(a));
        long distanceInMeters = Math.round(6371000 * c);
        return distanceInMeters;
    }

而下面的code是它是如何被使用的：

if(lastLat == -1 && lastLng == -1){
    lastLat = location.getLatitude();
    lastLng = location.getLongitude();
    lastTimeStamp = location.getTime();
    return;
}
long distanceInMeters = getDistanceBetweenPointsAndSetTotal(lastLat, lastLng, location.getLatitude(), location.getLongitude());
long timeDelta = (location.getTime() - lastTimeStamp)/1000;
long speed = 0;
if(timeDelta > 0){
speed = (distanceInMeters/timeDelta);
}
Log.d("Calculations","Distance: "+distanceInMeters+", TimeDelta: "+timeDelta+" seconds"+",speed: "+speed+" Accuracy: "+location.getAccuracy());

lastLat = location.getLatitude();
lastLng = location.getLongitude();
lastTimeStamp = location.getTime();

当我运行它，我得到以下从LogCat中输出：

When I run it, I get following output from that LogCat:

Distance: 0, TimeDelta: 0 seconds,speed: 0 Accuracy: 5.0

详细原因 目标消费者不应该有高品质的GPS芯片高品质的设备，因此总是得到一个非常准确的修复，当设备处于移动状态是不可能的。

Detailed Reasons The target consumers are not supposed to have high quality devices with high-quality GPS chips, thus always getting a very accurate fix when the device is on the move is not possible.

因此​​，我不希望依赖于 Location.getSpeed​​（）方法，因为我已经看到它给出的速度值仅在精度范围内的5〜8米。

I thus don't want to depend on the Location.getSpeed() method, since I have observed it gives out speed values only when the accuracy is in the range of 5~8 metres.

在正常范围内的精度我得到一般情况下是10-15米，而 getSpeed​​（）不给任何速度。即使 hasSpeed​​（）开始返回假的。

The normal accuracy ranges I am getting in general circumstances is 10-15 metres, and getSpeed() doesn't give any speed. Even hasSpeed() starts returning false.

我一直在摆弄我的头，围绕这件事超过3天，在这任何帮助将是深深的AP preciated。

I have been tinkering my head around this thing for more than 3 days, any help in this would be deeply appreciated.

许多在此先感谢！

推荐答案

我开发 MyTrails ，一个Android测绘和跟踪应用程序，并像你，我先是用很粗的位置API的谷歌认为可以在Android中，包括努力。

I develop MyTrails, an Android mapping and tracking app, and like you I struggled at first with the very crude location APIs Google has seen fit to include in Android.

hasSpeed​​（）为假时，GPS芯片不具有足够好固定根据dopler效果来计算速度。即使是这样，我平时不信任的速度，如果是小于5公里每小时左右。

hasSpeed() is false when the GPS chip doesn't have a good enough fix to compute speed based on dopler effect. Even when it does, I usually don't trust the speed if it's less than 5km/h or thereabouts.

我的方式处理速度的计算是采用粗低通滤波器：我记录一个指点杆每秒（和最低5米余，根据 LocationManager.requestLocationUpdates（），并计算出最近的速度，我回去几件样品得到一个具有足够的距离分开（但不超过30s之前），并执行你做了平均。

The way I handle speed calculations is by using a crude low-pass filter: I record a trackpoint every second (and a minimum of 5m apart, based on LocationManager.requestLocationUpdates(), and to calculate the recent speed, I go back a few samples to get one that is a sufficient distance apart (but no more than 30s prior), and perform the averaging you're doing.

我使用Location.distanceBetween（）的实际距离计算。要注意的是它不能在一个非常小的（但不幸的）数量的设备，所以半正矢方法，你有可能是一个更好的选择。你可能想，虽然检查它，我有什么是

I'm using Location.distanceBetween() for the actual distance calculation. Beware that it fails on a very small (but unfortunate) number of devices, so the haversine method you have may be a better bet. You may want to check it though, what I have is

/**
 * Gets distance in meters, coordinates in RADIAN
 */
private static double getDistance(double lat1, double lon1, double lat2, double lon2) {
    double R = 6371000; // for haversine use R = 6372.8 km instead of 6371 km
    double dLat = lat2 - lat1;
    double dLon = lon2 - lon1;
    double a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
            Math.cos(lat1) * Math.cos(lat2) *
                    Math.sin(dLon / 2) * Math.sin(dLon / 2);
    //double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    return 2 * R * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    // simplify haversine:
    //return 2 * R * 1000 * Math.asin(Math.sqrt(a));
}

（注意1000倍）

(note the 1000 factor)