## 3 Results
### Gait Analysis
#### 3.1.1 Stride Length and Velocity  
The subjects' stride length and speed were evaluated during the two walking tests, both with and without obstacles to be avoided. All subjects showed good ease and effectiveness in their gait and no skidding or stumbling was observed. The acquisition system, thanks to the high number of frames per second acquired, proved itself able to accurately follow the different phases of the subjects' walks, managing to identify their lower limbs' KeyPoints during the entire course of the tests. Figure 6 shows the two points of view for 3D reconstruction of two paired subjects walking.  
Figure 5: Test for assessing the subject’s gait skills. Top left image: input image. Top right image: the computed disparity map. Bottom image: how the system reconstructed the 3D scene where a subject was performing the test.  
As it can be seen, the gait posture of the patient appears sufficiently correct in the image from the lateral camera (Figure 6c), but an evident inclination of the trunk which strongly influences the motor skills of the subject can be seen in the image taken from the front camera (Figure 6d). Figure 7 shows the distance from the origin of the left and right foot computed from the system for one of the subjects involved in this study. For all patients, the values of stride length and speed measured during the tests were lower than those of the corresponding control subjects, as perhaps it was reasonable to expect, given the scores that were attributed to them by the clinician.  
In Figure 8, the graphs of distance between heels for two subjects, paired thanks to the strong similarity of their physical characteristics, are shown. The time difference between two consecutive curve maxima with odd or even indices gives the duration of each step.  
Figure 6: The two points of view for 3D reconstruction of one subject from the control group ((**a**): the subject walks from left to right; (**b**): the subject walks towards the camera) and one of the control patients ((**c**): the subject walks from left to right; (**d**): the subject walks away from the camera).  
Figure 7: Distance from the origin of left (blue) and right (orange) foot, respectively, for one of the subjects involved in the study.  
For this healthy control, an average stride length of 1.25 m was measured (with the lengths of their two steps differing by less than 1 cm) along with an average stride velocity of 1.22 m/s. However, for the PD patient, an average stride length of 0.82 m was measured (with the length of the two steps differing by about 3 cm) along with an average stride velocity of 0.88 m/s. Values measured for all the other subjects involved in the study are shown in Table 2.  
Figure 8: Plot of distance between heels for two paired subjects: (**a**) patient subject heels distance; (**b**) patient subject smoothed heels distance, where we apply smoothing to remove false positives and false local extremes; (**c**) extreme of the curve (**b**) located to compute stride features: the time difference between two consecutive maxima with even or odd indexes gives the duration of each stride; (**d**) control subject heels distance; (**e**) control subject smoothed heels distance, where we apply smoothing to remove false positives and false local extremes; (**f**) extreme of the curve (**e**) located to compute stride features: the time difference between two consecutive maxima with even or odd indexes gives the duration of each stride.