2.2.4. Sensor Placement Design

As discussed in the literature review, flatfoot is judged mainly by whether the MLA (medial longitude arch) drops. From the perspective of plantar anatomy, the drop of the navicular bone is the main cause, thus the regular position of the navicular bone should be referred to before designing the sensor placement. According to the statistics of the experiment, the position of the navicular bone falls between 60% and 65% of the whole foot, and the length of an adult's navicular bone ranges between 1–2 cm. Therefore, we decided to set 60% as the position of the navicular bone where the sensors were placed with the distance of 1 cm on the front and back. The sensors were placed in an array and numbered from 1 to 5 from the medial to the lateral, respectively. The illustration of the sensor placement and numbering is shown in Figure 4.
