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mmalekzadeh / motion-sense

MotionSense Dataset for Human Activity and Attribute Recognition ( time-series data generated by smartphone's sensors: accelerometer and gyroscope) (PMC Journal) (IoTDI'19)
https://www.sciencedirect.com/science/article/pii/S1574119220300201
MIT License
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Just a question #3

Closed ogreyesp closed 4 years ago

ogreyesp commented 4 years ago

Do data in folder Accelerometer_data comprise user acceleration + gravity combined in single values? i.e. these acceleration values are different to the ones encountered in A_DeviceMotion_data folder, isn't it?

Also I have noted that the length of Accelerometer_data files could be different to the ones in Gyroscope_data folder, Why? If the examples were sampled at the same frequency, the files would have the same size, isn't it?

mmalekzadeh commented 4 years ago

1) Accelerometer data is equal to user_acceleration+gravity in DeviceMotion data. They just come from different APIs in iOS. 2) What you are seeing is normal. Setting a sample rate in iOS (and Android) is just a suggestion to the operating system (i.e. iOS here). Since it is not a real-time system, the actual sampling rate for Accelerometer and Gyroscope can be a bit different, however very close to what we set that is 50Hz.

ogreyesp commented 4 years ago

Thank you so much for your quickly response.