## 2 Related Work
### LiDAR Sensors  
LiDAR (Light Detection and Ranging) sensors are another technology used for 3D scanning. LiDAR works by emitting laser beams and measuring the time it takes for the beams to reflect off objects in the environment and return to the sensor [17]. By measuring the time of flight of the laser beams, LiDAR sensors can obtain precise depth information about objects in the environment, which can be used to create 3D models.  
LiDAR sensors have been used in works from several application domains. [PERSON] et al. explored the use of various laser scanning technologies to assess damage to forest road surfaces [18]. The study focused on comparing the accuracy and applicability of three different laser scanning methods: Terrestrial Laser Scanning (TLS), hand-held Personal Laser Scanning (PLShh) with GeoSLAM ZEB Horizon and hand-held personal laser scanning with iPhone 13 Pro using 3D Scanner and Polycam apps. The research aimed to determine the effectiveness of these technologies in accurately mapping forest road surfaces and identifying damage compared to traditional tacheometric surveying methods. Specifically, the iPhone 13 Pro with 3D Scanner app demonstrated a positional height accuracy with a Root Mean Square Error (RMSE) of 0.185 m (X,Y) and 0.021 m (Z), while with the Polycam app, the RMSE was 0.31 m (X,Y) and 0.045 m (Z). The GeoSLAM ZEB Horizon achieved a (X,Y) RMSE of 0.108 m and a (Z) RMSE of 0.025 m. Comparatively, Terrestrial Laser Scanning (TLS) achieved the best results with a (XY) RMSE of 0.049 m and a (Z) RMSE of 0.0077 m. These results indicate that while TLS provides the most precise measurements, both the Apple's iPhone 13 Pro and the Geonorte's GeoSLAM ZEB Horizon scanners produce sufficiently accurate results for practical applications. The iPhone 13 Pro, in particular, offers a cost-effective and rapid alternative for assessing road conditions.  
The work discussed in [19] studied the viability of using Apple's iPad Pro's LiDAR and True-Depth camera systems as 3D scanning solutions compared to an industrial 3D scanner. The authors used different coloured Lego bricks to assess the accuracy of these technologies, focusing on shape and position tolerances. The data from the study revealed that the iPad Pro's LiDAR and True-Depth systems, while not as accurate as the industrial 3D scanner, still showed considerable potential. The industrial scanner consistently outperformed the iPad in terms of accuracy, but the iPad's technologies were deemed sufficient for specific applications where extreme precision is not a critical requirement.  
[PERSON] et al. presented a methodology for using a Digital Surface Model (DSM) within a VR environment focusing on its application in military operations in the Amazon [20]. The study details the use of an Unmanned Aircraft System (UAS) equipped with LiDAR sensors to gather data, which is then modelled using software like Blender and Sketchup. This model is used to create a VR environment for immersive terrain analysis, making it a simple and low-cost way to explore a DSM in VR. The paper highlights the potential of integrating modern technology like VR and UAS in strategic and tactical planning, particularly in difficult terrains, enhancing situational awareness and operational efficiency. Finally, the authors verified that a Ground Sample Distance (GSD) greater than 1.93 cm/pixel begins to present a significant loss of the terrain characteristics considered important.