Emerging technologies such as Internet of Things (IoT) can provide significant potential in Smart Farming and Precision Agriculture applications, enabling the acquisition of real-time environmental data. IoT devices such as Unmanned Aerial Vehicles (UAVs) can be exploited in a variety of applications related to crops management, by capturing high spatial and temporal resolution images. These technologies are expected to revolutionize agriculture, enabling decision-making in days instead of weeks, promising significant reduction in cost and increase in the yield. Such decisions enable the effective application of farm inputs, supporting the four pillars of precision agriculture, i.e., apply the right practice, at the right place, at the right time and with the right quantity. However, the actual proliferation and exploitation of UAVs in Smart Farming has not been as robust as expected mainly due to the challenges confronted when selecting and deploying the relevant technologies, including the data acquisition and image processing methods. The main problem is that still there is no standardized workflow for the use of UAVs in such applications, as it is a relatively new area. In this article, we review the most recent applications of UAVs for Precision Agriculture. We discuss the most common applications, the types of UAVs exploited and then we focus on the data acquisition methods and technologies, appointing the benefits and drawbacks of each one. We also point out the most popular processing methods of aerial imagery and discuss the outcomes of each method and the potential applications of each one in the farming operations.

The use of information technology in agriculture has brought significant benefits to producers, such as increased profits and better product quality. Modern technology applications in agriculture rely on the use of unmanned aerial vehicles (UAVs) and wireless ground sensors to provide real-time information about fields and crops. In Europe, these techniques, referred to as Smart Farming (SF), are still in their infancy despite the large agricultural production of a wide range of products. For this reason, in this study, we experimented with the technologies of SF in the cultivation of Greek saffron, a rare spice with many uses. For this reason, and also because its harvest is quite labor intensive, it is one of the most expensive spices. Since the field of SF is relatively new and has not yet been used for this particular crop and area, the equipment and methods of data processing were selected experimentally after a review of the literature. The aim of the study was to remotely acquire image data of the crops and train a machine learning model to detect important objects such as saffron flowers and weeds.