## 2 Related Work
This survey was restricted to sensors available on smartphones and problems such as direction indication and floor localization. An exciting part of the review indicates open questions, such as how to include autonomous resources in the system, integrate external monitoring systems, define maintenance policies, update maps, and continuously improve the performance of indoor positioning systems. [PERSON] et al., in their study, highlighted the difficulty of identifying addresses mapped using single sensor information or the use of a unique technique [38]. The research was directed to the combination of records established by different technologies in clusters to increase the representativeness of the records, which can assume static or dynamic characteristics. A concern of the authors in determining the arrangements is to balance the number of records activated to identify an address and the energy consumption spent by the settlement, even when observed in critical situations such as connection failures or the significant presence of noise. [PERSON] et al. indicated that there are currently many solutions available to assist in the navigation of people with visual impairments in previously known indoor environments [24]. The authors suggested that indoor environments have more significant complexities than outdoor environments, and alerts should be given more quickly to avoid accidents. In reviewing techniques used for navigation and guidance in closed environments, the authors evaluated and compared state-of-the-art in-house navigation solutions, and the implications of the research provide a summary of critical observations, some ideas, and guidelines for further development. It is essential to increase the perception of the target audience, increasing the acceptance of these devices. [PERSON] et al. [39], in their review, discussed the combinations of image processing techniques to create systems to map and locate indoor environments. The authors focused on solutions aimed at people with partial and total visual impairment to indicate the difficulties in providing fast and reliable responses. As a secondary theme of the work, the authors described that, in addition to the navigation process, which uses maps, other challenges require attention from researchers, such as the detection of obstacles present in the users' routes. Computer vision models that manipulate two-dimensional (2D) and three-dimensional (3D) images are considered in terms of perceiving barriers (horizontal and vertical obstacles) and concerning processing consumption and information delivery time. For this review, it was decided to provide details on technological and technical resources, describe the advantages and disadvantages of each one, and simplify and direct the reading, resulting in higher reliability of the information. Also, some classification schemes proposed in previous analyses are revisited to include information about the robustness of the concepts. For example, we considered [PERSON]'s study, which classified network-based and non-network-based IPS systems and initiated a discussion on hybrid models using schemes based on magnetic sensors [38]. Here, we include other technologies, such as magnetic fields, ambient light, and audible or non-audible sounds, supplied or not in an encoded format, fingerprints, and the most advanced current technology, computer vision. We were also concerned about indicating multisensory arrangements and algorithmic combinations in hybrid models. Each technological and technical approach is described in detail below.