Table 1. Characteristics of the research area on which we tested the effect of slope gradient on the mental workload of the harvester operator.
Location Azienda La Dogana
Municipality Barberino di Mugello
Province Firenze
Coordinates 44°03´N, 11°14´E
Category of cutting Late thinning
Species Douglas fir
Age [years] 50
Density [trees ha–1] 910
Stocking [m3 ha–1] 650
Mean removal tree DBH [cm] 24
Mean tree height [m] 25
Mean trunk volume of removed tree [m3] 0.48
Slope [%] 9–47
Table 2. Technical data of the Tobii Pro Glasses 2 Eye-tracker.
Eye-tracker
Sampling frequency 50–100 Hz (in respect to eye-trackers the sampling frequency means the number of identified locations of fixation points per second; this frequency determines the quality of results and the accuracy of measurements)
Cameras 4
Scene camera FOV 82° horizontally, 52° vertically
Scene camera parameters h.264; 1920 × 1080 pixels; @25 fps
Field of view 160°
Diagonal of scene camera FOV 90°; 16:9
Sound recording Yes
Weight 45 g
Battery 120 min
Recording Station
Connection HDMI, Micro USB, 3.5 mm Jack
Frequency 2.4 GHz & 5 GHz band
Dimensions 130 × 85 × 27 mm
Weight 312 g
1

Fig. 1. Tree cutting with the harvester on a 9% (a) and 47% (b) slope with heat maps of fixation points – when the eyeballs are in a state of relative rest and visual information is retrieved from the environment.

2

Fig. 2. Tree processing with the harvester on a 9% (a) and 47% (b) slope with heat maps of fixation points – when the eyeballs are in a state of relative rest and visual information is retrieved from the environment.

3

Fig. 3. The harvester moving on a 9% (a) and 47% (b) slope with heat maps of fixation points – when the eyeballs are in a state of relative rest and visual information is retrieved from the environment.

4

Fig. 4. Tree cutting with the harvester on a 9% (a) and 47% (b) slope with a gaze plot, showing the trajectories of fast movements between fixation points.

5

Fig. 5. One log of a tree processed with the harvester on a 9% (a) and 47% (b) slope with a gaze plot, showing the trajectories of fast movements between fixation points.

6

Fig. 6. The harvester moving on a 9% (a) and 47% (b) slope with a gaze plot, showing the trajectories of fast movements between fixation points.

7

Fig. 7. Duration of the harvester operator’s fixation during work in the stand with the analysed slope gradients.

8

Fig. 8. A fragment of a time series (a) and a periodogram – entire database (b) of fixation duration during the harvester operator’s work in the terrain with 9% slope gradient. View larger in new window/tab.

9

Fig. 9. A fragment of a time series (a) and a periodogram – entire database (b) of fixation duration during the harvester operator’s work in the terrain with 47% slope gradient. View larger in new window/tab.

10

Fig. 10. A fragment of a time series (a) and a periodogram – entire database (b) of fixation duration during the harvester operator’s rest period. View larger in new window/tab.