计算从信标距离时使用者在车辆正在移动 [英] calculate distance from beacon when user is moving in a vehicle
问题描述
如何使用BLE信标，如果用户在车辆使用2-15kmph速度移动？还有，如果距离不给我准确的结果来计算距离有任何其他机制的帮助，而我可以计算出最近beacon.The默认实现不给我正确的结果，因为在距离估计一个20秒的滞后。
其次，在这种情况下，应该ARMA过滤器使用。
How to calculate distance using BLE beacons if the user is moving in a vehicle with 2-15kmph speed?Also,if the distance won't give me accurate results is there any other mechanism with the help of which I can calculate the nearest beacon.The default implementation does not give me proper results as there is a 20sec lag in distance estimates. Secondly,in which cases should ARMA filter be used.
推荐答案
灯塔距离估计只是估计，所以你必须设置相应的精度要求。为了减少对无线电信号电平的噪声，许多样品进行平均一段时间
Beacon distance estimates are only estimates, so you must set accuracy expectations accordingly. In order to reduce noise on radio signal levels, many samples are averaged over a period of time.
搞清楚的适当的平均时间依赖于使用的情况下。正如你所提到的， Android的灯塔图书馆通过默认使用20秒滚动平均值。这使得基于车辆平均为过去20 seconds其中一个距离估计
Figuring out the appropriate averaging time depends on the use case. As you have noted, the Android Beacon Library uses a 20 second running average by default. This gives a distance estimate based on where the vehicle was on average over the past 20 seconds.
有关的车辆往上15公里/小时（约5公尺/秒）与50米的信标传输半径，这将是在信标时间最长为10秒的范围。有多少距离测量你需要得到什么？如果一个就够了，平均10秒以上。如果你需要更多的，设置甚至更短的时间。
For a vehicle going up to 15km/hour (~5 meters / sec) with a beacon transmission radius of 50 meters, it will be in range of the beacon for a maximum of 10 seconds. How many distance measurements do you need to get? If one is enough, average over 10 seconds. If you need more, set the period even shorter.
记者了解到，降低了采样间隔将增加更多的噪声误差的距离估计，因为你将有较少的统计样本的工作。有几件事情可以做，以使大多数你得到样品的：
Understand that reducing the sample interval will add more noise error to the distance estimates, because you will have fewer statistical samples to work with. A few things you can do to make the most of the samples you do get:
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设置灯塔，尽可能频繁地做广告。有些信标做广告以1Hz或更小，以节省电池。这导致差的距离估算。它提高到10Hz或更多，如果可能的。
Set the beacon to advertise as frequently as possible. Some beacons advertise at 1Hz or less to save battery. This leads to poor distance estimates. Increase it to 10Hz or more if possible.
关闭蓝牙配置性/可连接你的指路明灯。一些Android设备将只允许在连接模式下，每个BLE扫描一个信号电平样品（1.1秒默认库）。这可以在10赫兹失去了你90％的样本。
Turn off bluetooth configurability/connectability on your beacon. Some Android devices will only allow one signal level sample per BLE scan (1.1 secs by default in the library) in connectable mode. This can lose you 90% of your samples at 10 Hz.
配置信标发射机是在其最高功率设置，并正确校准。更强的信号具有更高的信噪比，得到更好的距离估计
Configure the beacon transmitter to be on its highest power setting and calibrate it properly. Stronger signals have a higher signal to noise ratio, giving better distance estimates.
该ARMA过滤器使用基于每个样品％的变化具有不确定性的采样间隔。它更适合用例缓慢移动的信标接收机。
The ARMA filter uses a nondeterministic sample interval based on % change in each sample. It is more appropriate for use cases with slow moving beacon receivers.
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