# Monitoring Safron Crops with UAVs
## 3 Field Study Design Methodology
### Equipment Selection  
UAVs have emerged as one of the most promising technologies for agriculture. The use of UAVs to monitor fields and investigate moisture and nutrient deficiencies in crops holds tremendous potential for farmers. Two different models were used for this study: Sensefly eBee SQ and DJI Phantom 4 RTK, whose main characteristics are listed in Table 2. The choice of the specific models was based on the different types of sensors attached and variance in other attributes, such as speed and range. The eBee model was chosen because of its ability to capture multispectral images that are used for vegetation health calculations and the relatively large flight duration. Since saffron is a small flower and needs to be monitored from low altitude for detailed images, the Phantom RTK quadcopter was selected to provide this capability.  
After the selection of the equipment, we had to decide on the optimal height of the flights. In this study, we experimented with three flight heights, (a) 400 m, (b) 120 m, and (c) 12 m. The test flights proved that the first height (400 m), in the case of saffron cultivations, cannot provide useful information, since the flower is very close to the ground, and the accuracy of the image is too low to provide information. Therefore, the data and images obtained from these flights were not used. The second height is ideal for performing long-distance flights that can monitor relatively large field areas. Images from 120 m can provide images that can be accurately estimated for the existence of animals, weeds, and saffron. Most of the flights were performed in this height in the context of this pilot study. The third height (12 m) is ideal for acquiring images for training the estimation models. In this case, the low height gives us access to high-accuracy images that can be precisely annotated by the experts. The images acquired for fields No. 2 and No. 3 were from this low altitude and were used to train the model.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Fields** & **Coordinates** & **Number of Flights** & **Number of Pictures** \\ \hline Field1 & 40.23398743, & & \\  & 21.85294092 & 5 & 529 \\ \hline Field2 & 40.24951173826714, & & \\  & 21.794159027924273 & 1 & 64 \\ \hline Field3 & 40.227257236926, & & \\  & 21.817700600381 & 16 & 315 \\ \hline Field4 & 40.23466, 21.84936 & 13 & 365 \\ \hline Field5 & 40.247819240092, & & \\  & 21.864312059633 & 14 & 290 \\ \hline Field6 & 40.171333751771, & & \\  & 21.870423160292 & 13 & 300 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The attributes of saffron fields that participated in the study.  
\begin{table}
\begin{tabular}{l c c} \hline \hline  & **Sensefly eBee SQ** & **DJI Phantom 4 RTK** \\ \hline
**Type** & fixed-wing & quadcopter \\
**Weight** & 1.1 kg & 1.39 kg \\
**Max speed** & 110 km/h & 58 km/h \\
**Flight control software** & eMotion Ag & DJI Pilot \\
**Image processing software** & WebDOM & WebDOM \\
**Sensors** & Parrot Sequoa+: & \\  & Multispectral, RGB & CMOS: RGB \\
**Maximum flight time** & 55 min & 30 min \\
**Range** & 3 km & 7 km \\ \hline \hline \end{tabular}
\end{table}
Table 2: Technical specifications of UAVs.