2.2.1. Data Acquisition

This study was based on the same dataset used in [21], which is publicly available in [31]. This dataset was composed of small sets of data (five seconds every five minutes) captured by the sensors available in the off-the-shelf mobile phones, i.e., accelerometer, magnetometer, gyroscope, microphone, and GPS receiver, and stored in the cloud. The dataset used in the presented study was created using an Android mobile application for data collection. On the one hand, the running and walking data were collected in outdoor environments. On the other hand, standing and going down and upstairs were performed inside buildings.

Moreover, the tests were conducted at different times of the day. In total, thirty-six hours of data were collected, which corresponded to 2000 samples with five seconds of raw sensor data each. Before data acquisition, the user had to use the smartphone to select the ADL that would be conducted and the time needed.
