使用线性加速度的android计算距离加速度、线性、距离、android
可能重复： Android加速度计精度（惯性导航）
我使用下面的code计算距离。 TNEW 和重新是的ArrayList 包含时间戳和加速分别为强。
I am using the following code to calculate the distance. tnew and anew are arraylists containing timestamps and accelerations respectively.
double distance=0;
double init_vel=0;
long time_prev=tnew.next();
while(anew.hasNext())
{
float temp_acc=anew.next();
long temp_time=tnew.next();
interval=(temp_time-time_prev)/1000f; //milliseconds to seconds
double fin_vel=init_vel+(temp_acc*interval);
distance+=(init_vel*interval)+0.5f*temp_acc*interval*interval;
init_vel=fin_vel;
time_prev=temp_time;
}
有没有在code任何逻辑错误呢？因为我得到的值比实际长度要小很多。
对 LogCat中输出：
Is there any logical mistake in the code? Because I am getting values much smaller than the actual length.
Output of LogCat :
--------- beginning of /dev/log/system
--------- beginning of /dev/log/main
V/PhonetapeActivity( 8842): Sensor Listener Registered
V/PhonetapeActivity( 8842): Sensor Unregistered
V/PhonetapeActivity( 8842): No. of Iterations : 49
V/PhonetapeActivity( 8842): Value of acceleration : 3.5762787E-7
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665585965
V/PhonetapeActivity( 8842): Value of acceleration : -0.15275347
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586017
V/PhonetapeActivity( 8842): Value of acceleration : 0.15585232
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586077
V/PhonetapeActivity( 8842): Value of acceleration : 1.075269
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586138
V/PhonetapeActivity( 8842): Value of acceleration : 3.6529458
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586199
V/PhonetapeActivity( 8842): Value of acceleration : 9.645137
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586257
V/PhonetapeActivity( 8842): Value of acceleration : 17.022213
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586316
V/PhonetapeActivity( 8842): Value of acceleration : 9.721476
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586376
V/PhonetapeActivity( 8842): Value of acceleration : -18.729362
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586437
V/PhonetapeActivity( 8842): Value of acceleration : -22.868385
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586497
V/PhonetapeActivity( 8842): Value of acceleration : -16.777517
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586557
V/PhonetapeActivity( 8842): Value of acceleration : -7.0492268
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586617
V/PhonetapeActivity( 8842): Value of acceleration : -3.860828
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586677
V/PhonetapeActivity( 8842): Value of acceleration : 1.7244682
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586737
V/PhonetapeActivity( 8842): Value of acceleration : 5.0734243
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586797
V/PhonetapeActivity( 8842): Value of acceleration : 6.4193974
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586857
V/PhonetapeActivity( 8842): Value of acceleration : 2.739545
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586917
V/PhonetapeActivity( 8842): Value of acceleration : 5.559997
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665586977
V/PhonetapeActivity( 8842): Value of acceleration : 4.2290807
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587037
V/PhonetapeActivity( 8842): Value of acceleration : 5.0012918
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587097
V/PhonetapeActivity( 8842): Value of acceleration : 5.9317436
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587157
V/PhonetapeActivity( 8842): Value of acceleration : 5.20226
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587217
V/PhonetapeActivity( 8842): Value of acceleration : 7.1381693
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587276
V/PhonetapeActivity( 8842): Value of acceleration : 7.6460614
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587337
V/PhonetapeActivity( 8842): Value of acceleration : 5.566694
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587396
V/PhonetapeActivity( 8842): Value of acceleration : 3.355657
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587457
V/PhonetapeActivity( 8842): Value of acceleration : 1.8876343
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587517
V/PhonetapeActivity( 8842): Value of acceleration : -0.8815446
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587577
V/PhonetapeActivity( 8842): Value of acceleration : -0.9595623
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587646
V/PhonetapeActivity( 8842): Value of acceleration : -4.233544
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587697
V/PhonetapeActivity( 8842): Value of acceleration : -1.9580669
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587765
V/PhonetapeActivity( 8842): Value of acceleration : -1.4569702
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587822
V/PhonetapeActivity( 8842): Value of acceleration : -0.6058636
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587876
V/PhonetapeActivity( 8842): Value of acceleration : -0.21207428
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587937
V/PhonetapeActivity( 8842): Value of acceleration : 0.5068469
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665587997
V/PhonetapeActivity( 8842): Value of acceleration : 5.614555
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588057
V/PhonetapeActivity( 8842): Value of acceleration : -4.5297813
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588122
V/PhonetapeActivity( 8842): Value of acceleration : -0.29250193
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588178
V/PhonetapeActivity( 8842): Value of acceleration : -2.4922757
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588237
V/PhonetapeActivity( 8842): Value of acceleration : -1.7652755
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588297
V/PhonetapeActivity( 8842): Value of acceleration : -2.3279366
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588357
V/PhonetapeActivity( 8842): Value of acceleration : -1.8127642
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588419
V/PhonetapeActivity( 8842): Value of acceleration : -1.956768
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588477
V/PhonetapeActivity( 8842): Value of acceleration : -0.8337221
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588537
V/PhonetapeActivity( 8842): Value of acceleration : -0.24841261
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588601
V/PhonetapeActivity( 8842): Value of acceleration : 0.23997736
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588657
V/PhonetapeActivity( 8842): Value of acceleration : 0.14441395
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588723
V/PhonetapeActivity( 8842): Value of acceleration : 0.23150349
V/PhonetapeActivity( 8842): Value of timestamp(milli) : 1350665588777
V/PhonetapeActivity( 8842): 1st while loop ended
V/PhonetapeActivity( 8842): 2nd while loop ended
V/PhonetapeActivity( 8842): Avg value : 0.4006781578063965
V/PhonetapeActivity( 8842): Max Value : 17.022213
V/PhonetapeActivity( 8842): Min Value : -22.868385
V/PhonetapeActivity( 8842): Standard Deviation : -0.0031174493
V/PhonetapeActivity( 8842): 3rd while loop started
V/PhonetapeActivity( 8842): startpos=3 endpos=8
V/PhonetapeActivity( 8842): acceleration=0.1558523178100586 interval=0.061000000685453415
V/PhonetapeActivity( 8842): distance=5.799264876044276E-4
V/PhonetapeActivity( 8842): next init velocity=0.009506991493243078
V/PhonetapeActivity( 8842): acceleration=1.0752689838409424 interval=0.061000000685453415
V/PhonetapeActivity( 8842): distance=0.005160928954000712
V/PhonetapeActivity( 8842): next init velocity=0.07509840024458736
V/PhonetapeActivity( 8842): acceleration=3.6529457569122314 interval=0.057999998331069946
V/PhonetapeActivity( 8842): distance=0.021805144861910285
V/PhonetapeActivity( 8842): next init velocity=0.2869692480489858
V/PhonetapeActivity( 8842): acceleration=9.645136833190918 interval=0.05900000035762787
V/PhonetapeActivity( 8842): distance=0.07231105232279186
V/PhonetapeActivity( 8842): next init velocity=0.8560323246566197
V/PhonetapeActivity( 8842): acceleration=17.022212982177734 interval=0.05999999865889549
V/PhonetapeActivity( 8842): distance=0.18495295465057213
V/PhonetapeActivity( 8842): next init velocity=1.8773650807587172
V/PhonetapeActivity( 8842): 3rd while loop ended
V/PhonetapeActivity( 8842): final distance=0.18495295465057213
V/PhonetapeActivity( 8842): values of acceleration, timestamp, distance, start_time and calibrating reset
如果你观察logcat的，首先它通过加速度49值以及它们各自的时间戳以毫秒为单位迭代。然后有一个平均，总和，最大值，最小值等
如果你看到然后有一个 startpos = 3 和 endpos = 8 。这是迭代次数范围内，我使用的计算.IE我使用的加速和时间戳值的距离只能从迭代3到8 这是因为，我发现距离计算开始从上涨加速到突然变化向相反的方向。你可以看到，从3-8的价值观融入逻辑。从3存在着相当大的上升在加8后有一个突然下降。
If you observe the logcat, first it iterates through 49 values of acceleration and their respective time stamps in milliseconds. Then there is a avg, sum, max, min etc.
Then if you see there is a startpos=3 and endpos=8. This is the iteration number range, I am using to calculate the distance .i.e I am using the values of acceleration and timestamp only from iteration 3 to 8. This is because, I detect the start of distance calculation from a rise in acceleration to a sudden change in the opposite direction. You can see that the values from 3-8 fit into the logic. From 3 there is a considerable rise in acceleration and after 8 there is a sudden decrease.
推荐答案
加速度计是非常precise但坏的航迹推算。陀螺仪是善于发现，但他们漂移随着时间的推移。 传感器融合 是使用串联加速/陀螺仪数据的过程使用另一个正确的缺乏。 AFAIR，传感器融合是不是在银河王牌启用。 LINEAR_ACCELERATION 不过是 ACCELEROMETER - 重力因素。上无陀螺仪设备，融合不可能通过定义它需要加速+陀螺
Accelerometers are very precise but bad at dead-reckoning. Gyroscopes are good at that but they "drift" over time. "Sensor-fusion" is the process of using accel/gyro data in tandem to correct one's deficiency using the other. AFAIR, "sensor-fusion" is NOT enabled on Galaxy Ace. LINEAR_ACCELERATION is nothing but ACCELEROMETER - gravity component. On devices without gyroscope, fusion is not possible by definition it requires accel+gyro.
加速度数据中包含9.8重力因素。这个滤出通过简单地确定连续2样品加速度数据之间的差。这给我们的 LINEAR_ACCELERATION 数据。
The accelerometer data contains the gravity component of 9.8. This is filtered out by simply determining the difference between 2 consecutive samples of accelerometer data. This gives us the LINEAR_ACCELERATION data.
看一下实际的内部code：
frameworks/base/services/sensorservice/LinearAccelerationSensor.cpp
函数 LinearAccelerationSensor ::过程（）是在上面的文件感兴趣。
Check this out for actual internal code :
frameworks/base/services/sensorservice/LinearAccelerationSensor.cpp
The function LinearAccelerationSensor::process() is of interest in the above file.
还有基本的操作，如滤波/平均，上面的链接和视频谈，需要在你的应用程序中获得的加速度数据执行。以这种方式获得的处理后的值将是更好的（虽然不如将已obtaioned了传感器融合已经在设备上present的那些）比原始值。然后，这些可用于更准确地计算速度和位置。
Also rudimentary operations like filtering/averaging that the above link and video talk about, need to performed on the accel data obtained in your app. The processed values obtained in this manner will be better(though not as good as the ones that would have been obtaioned had sensor fusion been present on your device) than the raw values. These can then be used to calculate the velocity and position more accurately.
这是说，16个样本第二（@轮询率= 60毫秒），这本身就是相当不准确的。你可能会想尝试注册 sensorEventListner 使用 SENSOR_DELAY_FASTEST 看样，您可以为您的设备上获得的最大数量
That said, 16 samples a second (@poll-rate=60ms) is relatively inaccurate in itself. You might want to try registering the sensorEventListner using SENSOR_DELAY_FASTEST to see the maximum number of samples that you can obtain on you device.
另外请注意，在手机上的加速度计钳位到某些最大灵敏度（通常为 - / + 2/4/8 G系列）。而正常行走/跑步可能在这些范围内工作，在加速（例如骑自行车）一时冲动一定会夹到最大，你将失去同步的航迹推算。 / + MAX - 这可以通过注意样品是非常接近的数量进行检查。在样本的地段 - / + MAX意味着你将肯定失去同步，与实际位置
Also note that the accelerometers on phones are clamped to certain MAX sensitivity (usually -/+ 2/4/8 G range). While normal walking/running might operate under these ranges, a sudden impulse in acceleration (for example on a bike) will definitely be clamped to the MAX and you will lose sync in dead-reckoning. This can be checked by noting the number of samples that are very close to the -/+MAX. Lot of samples at -/+MAX imply that you would have most certainly lost sync with the actual position.
