# Time of Flight Distance Sensor-Based Construction Equipment Activity Detection Method
## 4 Results and Discussion  
### Performance Verification of the Proposed Model  
One sample comprises 200 sets of piston displacement ratio values, recorded as time series data over a 10-s period. Figure 6 shows the sample data matrices for each activity used in the classifier. As can be seen, the patterns of the six activities are visually distinguishable, and this clarity is reflected in the confusion matrix of the data classifier. The color pattern during the waiting state shows little change, but it is presumed that frequent color changes occur in the data from the bucket due to vibrations causing shaking (Figure 6a). Scraping is the action of pushing or collecting soil on the ground while maintaining a constant height. In Figure 6b, the fact that the overall color of the boom pattern is close to blue means that the excavator is moving while maintaining the boom in a lowered state close to the ground. In the bucket pattern, the movement changed frequently enough to change to orange three times, which means that when the arm is not moving, scraping is performed by manipulating the bucket. Excavating (under) and Excavating (front) both achieve the same result of putting soil into the bucket, but a clear difference can be seen through pattern analysis (Figure 6c,d). In the case of 'Under', the color of the boom pattern shifts from blue to yellow, signifying the action of significantly lifting the boom as it nears the completion of the activity. Conversely, in the case of 'Front', the color transitions from yellow to blue, denoting that the boom is \begin{table}
\begin{tabular}{l c c} \hline \hline
**Parameter** & **Value** & **Description** \\ \hline Gradient Decay Factor & 0.9 & Rate at which past gradients are decayed. \\ \hline Squared Gradient Decay Factor & 0.999 & Rate at which past squared gradients are decayed. \\ \hline Epsilon & \(1\times 10^{-8}\) & Constant added to prevent division by zero. \\ \hline Initial Learning Rate & \(1\times 10^{-3}\) & Starting learning rate for the training process. \\ \hline Max Epochs & 3 & Maximum number of epochs for training. \\ \hline Learning Rate Schedule & ‘none’ & Approach to adjusting the learning rate (constant in this study). \\ \hline Learning Rate Drop Factor & 0.1 & Factor by which the learning rate is reduced when scheduled. \\ \hline Learning Rate Drop Period & 10 & Epochs between learning rate reductions. \\ \hline Mini-Batch Size & 32 & Number of samples per gradient update. \\ \hline Shuffle & ‘once’ & Shuffling of the dataset before training. \\ \hline L2 Regularization & \(1\times 10^{-4}\) & Regularization factor to prevent overfitting. \\ \hline Gradient Threshold Method & ‘L2 Norm’ & Method for clipping gradients (not applied with ‘Inf’ threshold). \\ \hline Gradient Threshold & Inf & Threshold for gradient clipping. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Hyperparameter configuration for model training. undergoing a folding motion. The number of color changes and the intervals between them in the actions of the arm and the bucket demonstrate similar patterns. This similarity is analyzed to be due to the identical process of digging soil into the bucket and lifting it to prevent soil loss. In the 'under' scenario, beyond the initial phase (approximately 0 to 2.5 s), a piston length ratio of less than 50% for the arm and bucket was observed in most frames. However, in the 'front' scenario, a piston length ratio of more than 50% was observed in most frames. This difference occurs because the action taken to prevent soil loss from the bucket is consistent, yet the rotation angles of the arm and bucket that effectively prevent soil loss vary depending on the boom's position. As a result, although behaviorally similar patterns (sections of color change) are observed in both cases, it can be concluded that the actual actions differ significantly according to the pattern. Dumping refers to the process of transferring soil from a bucket to a specified location.