# RFID and Drones: The Next Generation of Plant Inventory
## 4 Discussion  
Tag scanning results varied depending on tag inlay type and size (Figures 13 and 14). Some of the tags scan rates were 70% lower than other tags. For example, Tag 80 total readings were 168, while 6F total readings were 527. Furthermore, Tag 6F had the highest number of scans and got the highest reading at SR and SL, while Tag 12 got the highest readings at DN and UP orientation. The highest number of scans at 7.6 m were tag 6F; at 6.0 m was Tag 9F; at 1.5 m was Tag 00, and at 3 m and 4.5 m was Tag 12. In addition, some tags inlay has a scan rate of 95% more, for example, at 7.6 m, Tag TDX (80) has 5 scans, while TDE (6F) has 231 scans.  
In the second laboratory experiment, all four orientations of Tags 9F and 6F did not have a significant effect on the total number of scans (\(p\)-value > 0.05) which showed that the two-tag design have good performance. Fifty percent of the tags at UP and SR orientation shows a significant result (\(p\)-value < 0.05) for Tags 5B and 12. Moreover, the DN and SL produced insignificant results (\(p\)-value > 0.05).  
Up to this point, the discussion has focused on comparing differences in the cumulative total of scans by different tags under both laboratory and field conditions. When the total is expressed as a rate (number of scans/unit time) an unexpected result is observed. If we use as an example Tag 6F, scan rate in the first experiment was 81 scans/min (527 total scans/6.5 min), while in the field experiment (VF), the same tag yielded 1 scan/min. A plausible explanation for this difference in the scan rate was due to the interference of signals (Remote Control, Transceivers, GPS) generated by various components of the sUAS system which were not an issue in the laboratory test.  
While in the HF experiment, the RFID reader was able to scan all tags in each altitude and in all 4 orientations except for Tag 6F. The results on the data collected also showed a huge difference in comparison to the laboratory experiment with regard to the orientation. For example, the scan total of Tag 6F at horizontal 90\({}^{\circ}\) SR position was 0, but in the laboratory tag 6F has the highest number of scanned in the same orientation. Furthermore, the results on the data collected show a difference with regard to the distance as well. Tag 6F has 0 scan in all 3 altitudes, but in the laboratory tag 6F has the highest scan.  
Two papers [15, 16] report on an RFID system similar to ours. [PERSON] and [PERSON] [15] built an integrated RFID system using the same RFID module we used. Our studies used the Moe chip while they used the development kit board of Moe. Our objective was to minimize the size of our RFID box and focus in developing our own drivers for the Mee. Although, their system was portable enough, it was not intended to be used where the RFID reader will be moving during operation as compared to our application. [PERSON] et al. [16] developed their own Arduino-based system and used two RFID chips from Atmel. Their system was unique as it used an easily fabricated antenna. While their antennae were small, the power of their system was very limited as their application was confined to small  
Figure 14: The total number of scans per tag type and orientation when the sUAS was flown with a fixed horizontal position at three different altitudes (4.5 m, 6.0 m, and 7.6 m) for 1 min.  
space. Our effort summarizes critical foundational efforts that will be used in future field experiments at a large commercial nursery. We acknowledge a possible limitation of our current system in flight time; however, we envision improvements in battery technology will advance in the future which will address this limitation.