*3.1. The Accuracy of Positions*

The mean of absolute errors of positions between those measured by u-blox ZED-F9P and control points was obtained as about 43 cm. The result of the one-sample t-test showed that the positioning accuracy of u-blox has no significant deviation from the area of logging trails (test value = 0.5 m, *p*-value > 0.05). However, the absolute errors are distributed between 1.5 cm to 1.8 m (Figure 4).

**Figure 4.** Distribution of absolute errors of positions recorded for u-blox ZED-F9P in control points.

#### *3.2. TreeNet Performance*

The optimal TreeNet model was obtained after building 490 trees with a learning rate of 0.011 and tree complexity of 7 (Figure 5). The ROC values were 0.977 for the training dataset and 0.745 for the testing dataset. It indicates that TreeNet demonstrated high performance for expressing the features that are determining the positioning accuracy of the GNSS receivers in forest.
