使用 Android GPS 位置纬度/经度准确计算车速 (MPH)

Question

我目前正在尝试开发一个 Android 应用程序，该应用程序使用来自 GPS 的位置纬度/经度以英里/小时 (MPH) 显示车辆的准确道路速度。

我有以下代码作为我的第一次尝试：-

private fun startLocationUpdates() {
    val locationRequest = LocationRequest.create()?.apply {
        interval = 1000
        fastestInterval = 500
        priority = LocationRequest.PRIORITY_HIGH_ACCURACY
    }

    fusedLocationClient.requestLocationUpdates(locationRequest, manufactureCallBack(), Looper.getMainLooper())
}

       @SuppressLint("SetTextI18n")
        override fun onLocationResult(locationResult: LocationResult) {
            locationResult.locations.forEach { location ->
                previousTimestamp = if (this@MainActivity::previousLocation.isInitialized) {
                    val dist: Double = HaversineAlgorithm.distanceMiles(previousLocation.latitude, previousLocation.longitude, location.latitude, location.longitude)

                    val currentTime = System.nanoTime()
                    val time_s: Double = (currentTime - previousTimestamp) / (1_000_000_000.0 * 60.0 * 60.0)

                    Timber.i("time_s = $time_s :: dist = $dist")

                    if (dist > 0.0 && time_s > 0.0) {
                        val speed_mps: Double = dist / time_s
                        Timber.i("${location.time} speed_mps = $speed_mps")
                        val speed_mph: Double = speed_mps * something
                        milesPerHourTV.text = "$speed_mph MPH"
                    }
                    currentTime
                } else {
                    System.nanoTime()
                }

                previousLocation = location
            }
        }

我的Haversine计算（Km）如下：-

fun distance(departureLatitude: Double, departureLongitude: Double, destinationLatitude: Double, destinationLongitude: Double): Double {
    val latitudeDelta = Math.toRadians(destinationLatitude - departureLatitude)
    val longitudeDelta = Math.toRadians(destinationLongitude - departureLongitude)
    val radiusDepartureLatitude = Math.toRadians(departureLatitude)
    val radiusDestinationLatitude = Math.toRadians(destinationLatitude)
    val a = sin(latitudeDelta / 2).pow(2.0) + sin(longitudeDelta / 2).pow(2.0) * cos(radiusDepartureLatitude) * cos(radiusDestinationLatitude)
    val c = 2 * asin(sqrt(a))
    return EARTH_RADIUS * c
}

到英里：-

fun distanceMiles(departureLatitude: Double, departureLongitude: Double, destinationLatitude: Double, destinationLongitude: Double): Double {
    val distanceInKm = distance(departureLatitude, departureLongitude, destinationLatitude, destinationLongitude)
    return distanceInKm * 0.621371
}

由于我在计算中只使用了两个点，因此我预计会出现“紧张”的结果，但是我看到的数字非常奇怪。

我正在考虑使用 Kotlin Flow 将我的位置更新发送到平均函数以平均位置并获得更准确的速度值。

我可以采取什么方法来获得更准确的速度？

我的计算有误吗？

Answer 1

我认为问题出在这里

 val currentTime = System.nanoTime()
 val time_s: Double = (currentTime - previousTimestamp) / (1_000_000_000.0 * 60.0 * 60.0)

你使用System.nanoTime()，它以纳秒为单位返回当前时间。

1 秒 = 10^9 纳秒

所以正确的解决方案是：

val time_s: Double = (currentTime - previousTimestamp) / 1_000_000_000.0