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PODetect programmatically if iPhone is dropped using CoreMotion/Accelerometer
 

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    <p>So I am writing a piece of code where I have to detect different movement gestures using Accelerometer and gyroscope in iOS 4.3 above.</p> <p><strong>Q1:</strong> Is there any existing opensource code which has achieved any movement/gesture detection?</p> <p>If not</p> <p><strong>Q2: For now I want to detect if the iPhone is dropped.</strong></p> <p><strong>What I have achieved so far:</strong> CoreMotion API gives <strong>userAcceleration</strong>, which (afaik) is <em>the acceleration that the user is giving to the device or the acceleration of device in some direction (x, y or z) with out considering the gravity</em> so what I can do is: store, let's say, previous 5-6 values of acceleration parameters and can check where any of them hits large negative value, which basically represents the sudden deceleration.</p> <p>But this solution is not very optimal, I think I need to somehow detect the freefall/downwards motion of the device too first. Any idea how to approach this problem?</p> <p><strong>UPDATE:</strong> Thanks Misch for sharing your approach. I was not at all thinking about total acceleration. I did exactly what you said:</p> <blockquote> <p>"You would however have to test yourself, what means "total acceleration corresponds approximately to earth acceleration" and "for some time" in your case."</p> </blockquote> <p>The acceleration value is actually in G's so I tested the "total acceleration" values with in range of 0.9 - 1.1. And I checked them over some time, initially I checked four consecutive values when updateInterval is set to 1/20.0. For now I have relaxed the condition of consecutiveness a little. </p> <p>Here's a sample output:</p> <p>Acceleration = 0.090868<br> Acceleration = 0.074473<br> Acceleration = 0.159797<br> Acceleration = 1.157513<br> Acceleration = 1.224588<br> <strong>Acceleration = 1.036272</strong><br> <strong>Acceleration = 0.914698</strong><br> <strong>Acceleration = 0.904093</strong><br> <strong>Acceleration = 0.941516</strong><br> Acceleration = 0.046362<br> Acceleration = 0.045109<br> Acceleration = 0.060045</p> <p>I think, I still have to keep on testing and adjusting values. If you have any optimization in mind kindly do share, I know in order to help you'd need to see the many samples of freefall acceleration values. For now I am thinking to:</p> <ol> <li>round off the values of acceleration to 3 decimal places and play with the acceleration range I am using.</li> <li>May be check if, after the freefall condition is met, total acceleration value suddenly goes down.</li> <li>Do you think the acceleration values I have quoted are a bit noisy? </li> </ol>
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    1. CO`if ([[UIScreen mainScreen] isGlassBroken]) { /* dropped */ }`
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    2. CO_"For now I want to detect if the iPhone is dropped."_ I wonder how you would test that feature.
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    3. COit's not a big deal, I've dropped my iPod a couple of time on carpeted floor :P I am not allowed to tell but this will be used in a very safe way. :)
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