## 2 Materials and Methods
### Parameters, Materials and Hardware  
Retroreflective foils are nowadays widely used, for example, on traffic signs. These foils reflect the impinging light back to its source with only minimal scattering. As in our previous works, we utilized the same off-the-shelf foils from the vendors 3M (production family 4000 [19]) and Orafol (VC170 family [20]). In the case of the 3M family, we use 5 different colors, whilst for the Orafol one, we applied 3 different colors. Table 1 summarizes the utilized foils with the respective vendor name, the color and the production code. Light-guiding microstructures are the basis of both types of foils to achieve the retroreflective characteristics. In addition, unaltered with respect to our previous work, we placed these retroreflective foils in different size configurations on the moving object. The moving object is the same adapted Lego train (60197 Lego City) that is formed by a black cuboid, which is 22.3 cm in length, 4.7 cm in width and 8 cm in height. The control block, the motor and the wheels with its connected platform were kept in their original state. In order to allow for longer runtimes, we changed the power supply to a rechargeable accumulator with a DC/DC converter. In the center of the platform, on top of the cuboid, the retroreflective foils were placed in the same way as in [14, 15]. The applied size configurations and the corresponding naming were not altered. Table 2 summarizes the size configurations and their corresponding names. In order to be able to directly compare the results of the previous work with the results discussed later in this manuscript, we also used the same speed levels with their corresponding names as given in Table 3.  
The applied speed levels largely coincide with the maximum speed levels of robotic platforms used in factory settings [21] or healthcare [22], which highlights the applicability of our work for future applications in regard to moving objects in the context of the IoT. By utilizing the same foils with the same size configurations and applying the same speed levels of the train, we can furthermore use the same naming conventions as in our previous works. To recapitulate, we defined a scenario as a distinct setup of the train in combination with the applied speed setting. The naming scheme always starts with the vendor of the respective foils at the beginning, 3M or Orafol. Concerning Orafol foils, we only use the abbreviation \"O\". The vendor is followed by the color of the respective foil. Then, the size configuration, according to Table 2, is given, which is followed by the applied speed settings of the train; see Table 3. To explain the applied naming scheme with an example, we use the scenario that is called \"O red Area 4 Speed 4\". This means that the \begin{table}
\begin{tabular}{c c c} \hline
**Vendor** & **Color** & **Production Code** \\ \hline
3M & Green & 4097 \\
3M & Blue & 4095 \\
3M & Yellow & 4091 \\
3M & White & 4090 \\
3M & Red & 4092 \\ Orafol & White & VC 170 \#015 \\ Orafol & Yellow & VC 170 \#065 \\ Orafol & Red & VC 170 \#012 \\ \hline \end{tabular}
\end{table} 
Table 1: Summary of the utilized retroreflective foils. \begin{table}
\begin{tabular}{c c} \hline Area 1 & 0.7 cm \(\times\) 4.7 cm \\ \hline Area 2 & 1.4 cm \(\times\) 4.7 cm \\ \hline Area 3 & 2.1 cm \(\times\) 4.7 cm \\ \hline Area 4 & 2.8 cm \(\times\) 4.7 cm \\ \hline \end{tabular}
\end{table} 
Table 2: Summary of the size configurations and the name of the size configurations. \begin{table}
\begin{tabular}{c c} \hline Speed 1 & \(\sim\) 0.68 m/s \\ \hline Speed 2 & \(\sim\) 0.81 m/s \\ \hline Speed 3 & \(\sim\) 0.94 m/s \\ \hline Speed 4 & \(\sim\) 1.06 m/s \\ \hline \end{tabular}
\end{table} 
Table 3: Applied speed levels and the average velocities of these speed levels. red Orafol foil in the size of 2.8 cm \(\times\) 4.7 cm was placed on the train and that the train was moving at an average velocity of \(\sim\)1.06 m/s.