# Monitoring Autonomous Mowers Operative Parameters on Low-Maintenance Warm-Season Turfgrass
## 2 Materials and Methods
### Assessments  
For a total of 26 days (from 13 September to 14 October 2021), the turf height in each plot was measured using a grass height meter after every moving event. Preliminary observations suggested that the height differed in the central area and at the corners. This led to three measurements at the corners and three measurements at the central point being taken on each plot (with three sub-repetitions). Data on the percentage of area moved, the distance traveled, the number of passages, and the number of intersections were collected through two Emlid Reach RTK (Emlid Tech Kft., Budapest, Hungary) devices mounted inside two custom-made cases (the rover and the base, which were extensively described by [PERSON] et al. [12]) to establish the remote sensing system. The data obtained were extracted and processed first by RTKLIB (version 2.4.3), then by the custom-built software \"Robot mower tracking data calculator\" version 1.8.0.0. (Qprel s.r.l., Pistoia, Italy). To determine whether there were preferential ways, the number of passages taken by the  
\begin{table}
\begin{tabular}{l l l l} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{3}{c}{**Autonomous Mowers**} \\ \cline{3-4}  & & **Automower 450X** & **Automower 535 AWD** \\ \hline Dimension (Length \(\times\) Height \(\times\) Width) & cm & \(72\times 31\times 56\) & \(93\times 29\times 55\) \\ \hline Mass & kg & 13.9 & 17 \\ Cutting height & cm & 3.5 & 3.5 \\ Hourly work capacity * & m\({}^{2}\)/h & 208 & 146 \\ Hourly electric energy consumption & kWh/h & 0.028 & 0.032 \\ \hline \hline \end{tabular}  
* Autonomous mowers (AMs) hourly work capacity refers to the manufacturer operator’s manual.  
\end{table}
Table 2: Autonomous mowers (AMs) operative characteristics.  
robots along their trajectories was also analyzed according to the cutting time and position, that is, passages in the center, the edge, and the corner of the plots, for several replicates equal to three for each position. On 14 and 22 September and 8 October, the tracker was used on the AM 450X; on 15 and 21 September and 8 October, it was used on the AM 535 AWD.  
The distance traveled as an operating parameter was used to calculate the equation of working efficiency:  
\[\text{Work Efficiency}=\text{Actual Cut Surface}/\text{Theoretical Cut Surface} \tag{1}\]  
Turf quality and color were visually assessed. Color values and turf quality were assigned based on a 1-9 colorimetric scale, with 1 for a light shade of green (very light green), 6 for an acceptable shade of green (acceptable green), and 9 for a dark shade of green (very dark green) [18]. Turf's quality 1-9 scale was adopted according to [PERSON] et al. [19], with 1 for \"bad\" quality turf, 6 for \"acceptable\" quality turf, and 9 for \"outstanding\" quality turf. The visual quality of the turfgrass was tested by measuring the Normalized Vegetation Index (NDVI) with a portable harvest sensor called a Handheld Crop Sensor (HCS--GreenSeeker, Model HSC-100, Trimble Navigation Unlimited, Sunnyvale, CA, USA). The protocol described by [PERSON] et al. [19] was followed, and it provided the NDVI value automatically calculated by the standard equation, where the reflectance in the red band (R) is correlated with the reflectance in the near-infrared (NIR):  
\[\text{NDVI}=((\text{NIR})-\text{R})/((\text{NIR})+\text{R}) \tag{2}\]  
The final surveys were conducted on 18 and 19 October 2021. Replication was threefold.  
Information on the resistance of soil penetration was gathered by the penetrometer (SC 900 Soil Compaction Meter, Fieldscout, Spectrum Technologies Inc., Aurora, IL, USA). Overall, 9 replicates were conducted to assess the ground penetration resistances at 5 different depths: 0.0 cm (surface), 2.5 cm, 5.0 cm, 7.5 cm, 10.0 cm.