## 2 Background
### iPad Pro LiDAR  
Numerous studies have evaluated the use of Apple's iPad Pro LiDAR in heritage conservation and architectural documentation. While its cost-effectiveness and portability make it a promising tool for rapid surveys, its accuracy is consistently found to be lower compared to professional-grade devices like photogrammetry and terrestrial laser scanners (TLS). [PERSON] [24] highlighted the sensor's suitability for simpler geometries but noted limitations in range (up to 5 m) and difficulty capturing fine details. Similarly, [PERSON] et al. [10] found significant inaccuracies in small, complex objects, with up to 50% of points misaligned, though the sensor performed well in simplifying larger architectural features like walls and facades. [PERSON] et al. [9] emphasized its usability for preliminary surveys but underlined its reduced precision compared to TLS, making it better suited for broaderheiritage documentation tasks. [PERSON] et al. (2018) identified challenges such as surface splitting and inertial navigation drift, highlighting the need for improved calibration to address movement-induced errors. [PERSON] et al. (2018) pointed out that the reduced range and point density of the iPad Pro's LiDAR limit its suitability for detailed documentation, while [PERSON] et al. (2018) demonstrated its adequacy for basic applications but not for highly detailed scans. [PERSON] et al. (2018) assessed its positional accuracy, finding it appropriate for mapping at a scale of 1:200 but with noticeable noise in point clouds. While these studies demonstrate the potential of Apple's LiDAR sensor (Lumentum, San Jose, CA, USA) in heritage documentation, they reveal several limitations:  
* Accuracy and Precision: The iPad Pro LiDAR sensor struggles with complex geometries and fine details, particularly when compared to photogrammetry or professional TLS. Calibration techniques specific to the sensor are limited, creating a need for more sophisticated methods to enhance precision in scanning heritage structures. * Limited Range and Data Density: The LiDAR's range is restricted to 5 m, which limits its usability in larger or taller heritage buildings. The reduced point density also affects the quality of the 3D models produced. * Error Mitigation in Field Scans: Drift issues and surface splitting in mobile scans have been identified, but robust solutions to mitigate these errors during fieldwork are still lacking. In addition, the 3D model development quality depends on a set of parameters to be controlled during the capture process (2018). Following the 3D accuracy modeling analysis developed by [PERSON] et al. (2018) the main parameter for 3D modeling to be considered is the distance to the object. Other parameters considered for the model developing include: sensor angle, scanning time, number of passes, lighting, and scanning resolution. These parameters are summarized in Table 1 with the addition of the type of material of the scanned object and the software used for model processing in the main works in the literature. The analysis of Table 1 shows that the distance to the object generally ranges from 1 to 5 m, which is the typical maximum range for these devices. Sensor angles present a significant variation in the literature, but most studies adopt perpendicular or varied angles to ensure better data capture. Scanning times fluctuate significantly, from a few minutes (around 4 min for lower resolution) to up to 20 min for higher resolution scans with multiple passes. Lighting is generally not a major limiting factor, with scans performed in both natural outdoor and controlled indoor environments. Resolution varies from 1 cm for high-detail settings to as low as 5.2 cm for less detailed scans, with most studies achieving a precision of around 1-2 cm, suitable for applications like architectural surveys. The common thread of the summarized works is the promise of portable, low-cost, and efficient scanning with accuracy close to professional-grade tools in ideal conditions. To identify