## 2 Materials and Methods
### Study Area and Surveying Methods  
This study was conducted in three specific areas of some olive orchards of a farm located in the area described above (42\({}^{\circ}\)46\({}^{\prime}\)15\({}^{\prime\prime}\) N, 12\({}^{\circ}\)46\({}^{\prime}\)41\({}^{\prime\prime}\) E). The considered orchards contain 4 typical and widespread Italian cultivars: Frantoio, Leccino, Moraiolo, and Maurino [33]. A different size can be observed among the four cultivars, which is consistent with their typical characteristics: \"Frantoio\" and \"Leccino\" are generally larger; \"Moraiolo\" is smaller, and \"Maurino\" is even smaller. These olive trees are trained using the \"vase system\" typical of the traditional rain-fed orchards, with 3 or 4 main branches growing from the trunk with an upward and outward inclination, to facilitate a wide interception of light for the optimization of photosynthesis. This shape also allows for an easy and efficient harvesting of the olives, which are carried out manually, with pneumatic or electric combs on poles, or by means of a trunk shaker machine. The first area, hereafter referred to as Area 1 (Figure 5), contains almost 1000 olive trees and is divided into two portions; the portion towards the north-east was 14 years old at the time of the survey and featured a prevalence of the Leccino cultivar with alternating rows of \"Frantoio\" and \"Maurino\"; the portion towards the south-west was 12 years old at the time of the survey and was characterized by a prevalence of the Moraiolo cultivar and two rows of \"Maurino\". Figure 6 shows the different cultivars in Area 1. The plants are distributed with a 6 \(\times\) 6 m planting distance, and each row contains a single cultivar. In this area, a sample of about 600 olive trees was selected for the study. Further analyses were conducted in two additional regions, Area 2 and Area 3 (Figure 5), encompassing a total of forty olive trees. These analyses were specifically designed to account for the varying impact of terrain slope on shadow patterns, which was crucial for the accurate measurement of tree heights. In particular, Area 2 was characterized by flat soil, and a sample of 20 olive trees of the Leccino cultivar was selected for this study; these olive trees were 22 years old at the time of the survey, and the planting distance was 5 \(\times\) 7 m.  
Figure 4: GCP distributions: the red points and the corresponding arrows indicate some examples of the measured GCPs. In contrast, Area 3 featured a steep slope, and a sample of 20 olive trees belonging to an ancient varietal selection was selected, attributable mainly, but not exclusively, to the Moraiolo cultivar; these trees were 68 years old at the time of the survey, and the planting distance was 6 \(\times\) 6 m.  
The orchard in Area 1 was surveyed using UAV photogrammetry to obtain point cloud data serving as the ground truth reference. In particular, the survey was performed in July 2023, the same time as the satellite image acquisition, with a DJI Phantom 4 RTK multispectral drone [34]. The flight plan was designed with the DJI GSPro app, (Apple iPad Pro 11', fourth generation, version 17.5), with a 75% overlap in both side and heading directions and a flight speed of 5 m/s. The flight altitude was set to 30.7 m, achieving a Ground Sample Distance (GSD) of 1.6 cm/pixel. The DJI Phantom 4 RTK multispectral captures images with an imaging system that includes an RGB camera and a multispectral camera with five sensors that cover the following bands: blue (B), green (G), red (R), red edge (RE), and near-infrared (NIR). For precise positioning, the drone was used with a D-RTK2 high-precision GNSS mobile station [35], an RTK base station capable of centimeter-level accuracy, supporting GPS, BEIDOU, GLONASS, and Galileo satellite systems. Figure 5: Study areas. Figure 6: Cultivars distribution in Area 1. Regarding the additional analyses in Area 2 and Area 3, more detailed photogrammetric UAV surveys were available.