# 3D Path Planning Algorithms in UAV-Enabled Communications Systems: A Mapping Study
## 3 Methodology: Mapping Study
### Planning
#### 3.1.3 Inclusion and Exclusion Procedure  
The inclusion and exclusion process are filters used to exclude studies that are irrelevant to answer the research questions (RQs). To select the 1233 documents found in the first search string, a filter must be carried out with the inclusion and exclusion criteria in an automated and manual way that allows adequate information collection. * **Automated inclusion-exclusion:** The inclusion-exclusion criteria can be automated and must have the following parameters: document type, language, years of publication, and subject area. 1. **Document type:** The selected documents are journal articles, conference articles, and literature reviews. 2. **Language:** Only English was selected because it is a universal language, and most relevant works are published in this language. 3. **Years of publication:** To select the most up-to-date documentation, the documentation of the last four years is chosen (i.e., from 2019 to 2022). 4. **Thematic area:** The area of our interest is Engineering and Computer Science. Once the filtering with the automatic inclusion-exclusion criteria is carried out, a new search string is generated, which is as follows:  
_\"3D path planning\" OR \"3-D path planning\" OR \"3 D path planning\" AND \"ULAV\" OR \"DRONE\" OR \"Unmanned aerial vehicle\" AND (LIMIT-TO (PIBYEAR, 2022) OR LIMIT-TO (PUBYEAR, 2021) OR LIMIT-TO (PUBYEAR, 2020) OR LIMIT-TO (PUBYEAR, 2019)) AND (LIMIT-TO (DOCTYPE, \"ar\") OR LIMIT-TO (DOCTYPE, \"cp\") OR LIMIT-TO (DOCTYPE, \"re\")) AND (LIMIT-TO (SUBJAREA, \"ENGI\") OR LIMIT-TO (SUBJAREA, \"COMP\")) AND (LIMIT-TO (LANGLIAGE, \"English\"))_  
Once this new search string was applied, the result of selected documents was 631, as seen in Figure 7.  
Figure 6: Search string with keywords in Scopus. Figure 7: Search string with automatic inclusion-exclusion criteria. * **Manual inclusion-exclusion:** For the manual inclusion-exclusion criteria stage, the filters executed are the study researchers' decisions. A decision tree makes it possible to be clear about the types of criteria applied at this stage, as shown in Figure 8.  
The decision tree describes the processes that must be considered for the manual classification of the documents to be analyzed in this study. Of the 631 articles selected in the automated filtering stage, it is required to determine if these documents are primary (Primary Contribution: These are sources where the information provided has been published for the first time, resulting from intellectual work on a research topic or secondary (Secondary or Tertiary Contribution: Secondary sources are those that have primary, synthesized, and reorganized information. They allow knowing facts from data collected by others, whereas tertiary sources contain and summarize various primary and secondary sources to provide an overview of a given research topic [25]) contributions, belong to the domain of the research topic, and are related to 3D UAV path planning techniques. Suppose there are doubts about the classification of a document. The document is undoubtedly included for further coding if the contribution meets the three main characteristics specified in the decision tree. Contrary to this, if the paper only meets one or two of the three attributes of the decision tree, the document should be excluded. In that case, it can be marked as \"Unclear\" and subsequently analyzed to define whether or not it is included in the group of documents to be coded. Table 3 shows the list of inclusion-exclusion criteria used to evaluate the documents. It will be included if the paper meets all the requirements, but if any exclusion criteria are maintained, then the document is excluded. With the list of the 631 documents obtained in the automated inclusion-exclusion classification of the Scopus database, the free web tool \"CADIMA\" is used, which allows the manual inclusion-exclusion of the documentation to be carried out safely.