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I am trying to record accelerometer values for a project using my smartphone. At static (phone completely at rest), attached file shows the readings I am seeing. I understand that this is not the most accurate accelerometer and there will be noise (which probably reflects the flickering value of all axes), but: 1. Why is the z value ~9.5m/s2 and not 9.81 m/s2? 2. Why arent x and y values completely 0 m/s2. x is closer to 0 but y is ~0.2m/s2.

I made sure my phone is as close to level in x and Y as possible. I know i need to apply some sort of smoothing to the data to take out the noise but why isnt the z axis exactly 9.81 m/s2? EDIT: Phone is a Samsung Note 4 Trace of the data

Omi
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  • Related: https://stackoverflow.com/a/4880733/295004 and an even older post: https://stackoverflow.com/questions/1638864/filtering-accelerometer-data-noise – Morrison Chang Oct 23 '17 at 19:47
  • I saw this post. It is a good explanation for how to take noise out. But it does not explain why the value of gravity is being reported as 9.5 instead of 9.81 m/s2. – Omi Oct 24 '17 at 12:33
  • You don't mention what device/OS you are using (many different Samsung phones). Honestly you could either have a bad device or one that has over time become mis-calibrated. Regardless the If you need 'accuracy' you can calculate the offsets in your app as a setup step similar to how you are doing your testing. – Morrison Chang Oct 24 '17 at 17:25

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