Human Activity Dataset Generation - Smartphone-Based Human Activity Recognition - page 59

Fig. 4.2 9X2 inertial sensor

mean age of all volunteers was 28 6years. Each person was instructed to fol-

low a protocol of activities while wearing a waist-mounted SGSII smartphone. The
experiment was planned in order to contain six BAs: three SPs ( standing, sitting,
lying-down ) and three AAs ( walking, walking-downstairs and walking-upstairs ).
Moreover, it was arranged with the intention of having also available all the possible
PTs that occur between the three existing SPs. These are: stand-to-sit (StSi), SiSt, sit-
to-lie (SiLi), lie-to-sit (LiSi), stand-to-lie (StLi), and lie-to-stand (LiSt). Figure 4.3
shows images of one of the experiment participants while carrying out the six BAs.
The protocol of activities is detailed in Table 4.2 . It includes all the tasks in sequen-
tial order and the time expected to be spent on performing each of them. Each subject
performed the protocol of activities twice: on the first trial the smartphone was fixed
on the left side of the waist, approximately 45% away from the anterior direction.
On the second trial the belt with the smartphone was placed by the user himself as
preferred. For the AAs, participants were told to remain standstill in between these
tasks in order to facilitate the labeling of the ground truth. This also supported the
repeatability of the test as in this way every activity was at least tried twice. Similarly,
this period was required after the last SP (lying-down) in order to fully capture the
LiSt PT.
The duration of the entire experiment was around 15 min per person including
the setting up of the sensors and the repetition of the protocol. Although the tasks
were carried out in laboratory conditions, volunteers were asked to perform freely
the sequence of activities aiming to simulate a more naturalistic dataset. All the
experiments were recorded on video with the consent of the participants in order to
have a ground truth of the performed activities. It was done with the video camera
of another smartphone at a frame rate of 30Hz.

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