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POCalculating distance using Linear acceleration android
 

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  1. POCalculating distance using Linear acceleration android
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    <blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/7829097/android-accelerometer-accuracy-inertial-navigation">Android accelerometer accuracy (Inertial navigation)</a> </p> </blockquote> <p>I am using the following code to calculate the distance. <code>tnew</code> and <code>anew</code> are <code>arraylists</code> containing <strong>timestamps</strong> and <strong>accelerations</strong> respectively. </p> <pre><code> 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; } </code></pre> <p><br> Is there any logical mistake in the code? Because I am getting values much smaller than the actual length. <br><br> Output of <code>LogCat</code> : <br></p> <pre><code>--------- 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 </code></pre> <p><br> 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. <bR> Then if you see there is a <code>startpos=3</code> and <code>endpos=8</code>. 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. <br>This is because, I detect the start of distance calculation from a <strong>rise in acceleration</strong> to a <strong>sudden change</strong> 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.</p>
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    1. COSee my [answer here](http://stackoverflow.com/a/7835988/341970) why.
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    2. CO@Ali : But this link says that he is getting accurate results using accelerometer - http://stackoverflow.com/questions/7858759/android-type-linear-acceleration-sensor-what-does-it-show
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    3. COI don't see where it is written he gets accurate results after the double integral (what you are trying to do).
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