## 4 Results  
### Signal Degradation Due to Foliage  
In the following discussions, RINEX 3 data collected from the GNSS receiver on the excavator during 12:00 h on 3 September 2022 to around 10:00 h on 5 September 2022 were used for analysis. During this period, the excavator was stationary, and therefore, this is referred to as the'stationary period' in multiple places in the document. The excavator at the beginning of the experiment on 3 September is made to face north, as mentioned before. Figure 2 shows the GNSS satellite visibility. During 40 percent of this time duration, 11 GPS satellites were visible, and 8 Galileo satellites were visible 50% of the time. A minimum of 5-7 satellites/constellations (GPS, Galileo and Glonass) and 22 satellites in total were visible almost all of the time during this period. One-second sampled observation data from the excavator and IGS broadcasted navigation data were together used to calculate dilution of precision values and these are plotted along with the number of visible satellites in Figure 3. As can be seen from Figure 2, except a few occasions, the DOP value remains below 2.5. Signal strength indicators (SSI) obtained from 1 s sampled RINEX 3 data files have been used here as a measure to understand the shadowing environment around the GNSS antenna mounted on the excavator. Figure 4 show plots of the SSI measurements on different frequencies and channels for GPS satellite G04 during the stationary period. Figure 1: The experimental set up. (**a**) The GNSS antenna marked with a green circle on top of the excavator. (**b**) Top view of the excavator showing the GNSS antenna. (**c**) The excavator facing NW direction with the tree on the right and the house on the left. Figure 2: GNSS satellite visibility. From Figure 4, it appears that C2W and L2W, which are the traditional GPS L2 signals, are weaker in strength than the L2C and L1 C/A signals. SSI values typically range between one and six, which means that the SNR for these signals range between a high of 36-41 dBHz to as low as less than 12 dBHz. Further analysis shows that this weakness of traditional L2 signals is found to be consistent for signals received from all of the GPS satellites. For some satellites, the SSI values for these signals have a maximum of eight or nine. But such cases are few and the time duration for such good signal strength is also very limited. Also from Figure 4, both C2W and L2W seem to be unavailable during certain periods between 2:00 and 3:00 h on 4 September and this is repeated also on 5 September. Also, the pseudorange signals on C1C and C2L seem to be less affected. The anomaly in the SSI measurements of G04 can be further confirmed with a skylplot showing the visibility of the satellites to the excavator antenna during 2:00-3:00 h on 4 and 5 September, and such a skylplot is shown in Figure 5.  
As can be seen, the satellite is visible in the NW direction of the excavator during a certain period of time. It is possible that an obstruction (such as a tree) located in this direction blocks the line of sight from the satellite to the receiver antenna causing the drop in signal strength visible in Figure 4.  
Figure 6 shows the plot of the SSI for the pseudorange measurements from G04 over varying azimuthal angles around the receiving antenna (during the stationary period). Figure 4: SSI for GPS satellite G04 during the stationary period (3–5 September 2022). Figure 3: Plot of number of visible satellites and different dilutions of precision (GDOP, PDOP, HDOP and VDOP) as seen at the receiver on the excavator. One can notice anomalous C2W values already at 305\({}^{\circ}\) and a total loss of signal strength between 313 and 320\({}^{\circ}\) and again between 322 and 329\({}^{\circ}\). Similar patterns of signal degradation at these azimuthal angles (around 300-350\({}^{\circ}\)) can be noticed for other GPS satellite signals such as those of G07, G09, G10, G14, G18, G23 and G29, as is clear from Figure 7a. Figure 7b clearly shows that C2L performance is much better than C2W.