# Revolutionizing Palm Dates Harvesting with Multirotor Flying Vehicles
## 1 Introduction  
Date palm trees (Phoenix dactylifera) are tall trees that grow to heights of up to 24 m [1]. They are characterized by cylindrical stipes (trunks) over which a crown of leaves develops. Among the leaves are the branches that carry the sought-after date fruits. Date palm is cultivated in over 30 different countries with production totaling approximately 9.7 million tons [2, 3]. The Kingdom of Saudi Arabia is among the top producers of dates with an annual yield of approximately 1.5 million metric tons [4]. The kingdom is estimated to have over 31 million date palm trees [4] distributed across various regions of the country. There are thousands of date farms in the Kingdom ranging from small family-owned farms to large commercial operations. These farms are spread throughout the country, with significant concentrations in regions like Al-Qassim, Al-Ahsa, and Al-Madinah [5]. Despite the huge production, harvesting of date palm has seen little advancements with regard to mechanization. For instance, the majority of the harvested date palms worldwide are done manually. This usually involves a harvester, with a rope wrapped around his back and the date palm trunk, climbing the trees and manually harvesting the fruit [6, 7, 8, 9, 10] as shown in Figure 1. The actual harvesting may involve plucking the fruits one by one, shaking the bunch to cause the fruits to fall, or cutting the entire bunch when they are deemed to be ready for harvesting [11]. Each of these techniques requires a skilled harvester, is physically demanding, and is quite dangerous. In some instances, harvesters utilize ladders, which enable the harvesting of date fruits for shorter palms. Ladders are also used to reduce the climbing to the upper section of the high palms and they are generally utilized without safety measures and may be more dangerous than theclimbing method. Tragically, numerous accidents have occurred, resulting in fatal falls from these towering trees [12]. Various mechanical systems employing hydraulic lifts and additional apparatus such as forklift towers and cranes have been employed to access dates on lofty trees [13; 14], Figure 2. There have been endeavors to adapt industrial machinery for date palm harvesting, particularly in the Kingdom of Saudi Arabia [9; 15; 16; 17]. However, these machines come with substantial costs and require a substantial workforce to operate. Furthermore, their ability to reach exceedingly tall trees is limited, imposing constraints on their utility. Moreover, workers may be unavailable in certain situations, such as during the COVID-19 crisis, which greatly reduced the date harvesting process and caused significant losses. An alternative approach involved the utilization of portable date bunch harvesting machines operated from the ground, as documented in [9]. This method entails the use of an electric saw to sever date bunches at a maximum height of approximately 8 m, followed by the retrieval of the branches. Some researchers have advocated for the deployment of robotic arm manipulators affixed to ground vehicles for date palm harvesting [7; 16; 18]. However, these ground vehicles are often cumbersome and may encounter difficulties traversing dense palm tree fields [19]. Moreover, the manipulator arms have finite reach capabilities, rendering them inadequate for harvesting exceptionally tall trees, Figure 3.  
After an extensive search in the literature, the authors were only able to identify a few studies addressing the modernization of date harvesting as is the case with other fruits such as apples [20; 21; 22; 23; 24; 25; 26; 27]. This is despite the enormous production of dates annually and the costs and risks involved in the widely used traditional procedure for date harvesting. As for the previously mentioned date harvesting approaches and proposed tools, they have faced limited adoption, particularly on smaller farms, for several reasons:  
1. Costly investment: The expense associated with these machines constitutes a significant barrier to their widespread use. 2.