## 1 Introduction
VOSviewer 1.6.18 software was used to perform cluster analysis on titles and abstracts (this choice is due to the lack of keywords in some of the works considered) having a frequency of at least six (Figure 2). A temporal analysis of the period under consideration (beginning of 2000-end of March 2022) was performed. However, the software detected significant occurrences only from 2014-2015, also considering the small number of articles in the first decade of the 2000s. According to the content of word occurrence, three clusters were obtained, and in line with what is covered in this review, the most common were \"UAV imagery\", \"image\", and \"olive tree\" followed by \"olive orchards\" and \"accuracy assessment\". The connection is well evident between \"UAV imagery\" and \"accuracy assessment\" to which the terms \"classification\" and \"object-based image analysis\" are associated with the topic of tree detection. This connection is well-established in the pre-2017 period. Of note is the presence of the name \"Spain\", indicative of the distribution of scientific work on RS in olive growing over the two decades under consideration. Figure 3 highlights the preponderant research occurrences in Spain (31), followed by Italy (17), but also a gradual broadening of research (and the increasing importance of the olive growing) in countries where olive crops are not traditional, such as Chile, Argentina, Peru, China and Australia. Figure 1: The trend of published articles based on publication year. The sources for the search of works reviewed were the following databases: Scopus (Elsevier) Google Scholar, and Web of Science (Clarivate Analytics). The \(x\)-axis shows the years of the period under consideration while the \(y\)-axis shows the number of researches carried out. In this review the researches considered are those carried out from the beginning of the year 2000 until the end of March 2022. Of the 72 researches in the time span analyzed, only 12 concern the years before 2011 and almost all (11) are based on tree detection and counting. The largest number of researches were carried out in the years 2020 (11) and 2021 (13). Figure 2: Keywords occurrence and clustering by VOSviewer 1.6.18. Colors indicate the year in which each title and words contained in the abstracts were more used. Lines represent co-occurrence link strength among terms. Figure 3: The map shows the worldwide geographical distribution of olive cultivation and the distribution of research study sites according to the countries reported in the published papers. The main olive producer countries are highlighted in dark green, while the main emerging producer countries are highlighted in light green. The symbols of different color (shown in the upper right) distinguish the type of remote sensing (RS) platform used (satellite, airborne, or unmanned aerial vehicle) in the research and the number of researches performed from 2000 to the end of March 2022. The table at the bottom left shows the number of remote sensing researches in olive growing carried out in each country. Important to consider that some researches include the use of more than one RS platform. The different words identified by [PERSON], although found in some of the topics covered in this review, do not allow to encapsulate all of them. Keywords related to the topic of tree detection and phenotyping and monitoring of biophysical parameters are present. Just think of the words \"tree detection\", \"tree height\" and \"tree volume\" alone. However, connections to other topics that could not be overlooked given the goal of this review are missing: pruning, yield, disease detection, and pest management. Specific sections will be devoted to these topics as well.