Apple's iPad Pro sensors for Cultural Heritage Documentation - First tests and results

The Documentation of Cultural Heritage (CH) is a complex process, since it requires a trained professional to manage expensive equipment such as Terrestrial Laser Scanner or drones, while CH itself is generally accessible by everyone, with a small ticket fee or for free. Therefore, the democratisation of this procedure could benefit the whole population, by enabling non-expert users to survey CH with a low-cost and mass-distributed solution to create 3D models of monuments or environments. Instead of using a high-cost laser scanner, the operator could exploit the LiDAR (Light Detection and Ranging) sensor equipped from 2020 by Apple in the camera module of iPhone and iPad Pro versions, to obtain models with a satisfying level of accuracy at a fraction of the cost and embedded in devices owned by a vast portion of the population. If the scenario of democratic documentation came true, the amount of people to access this feature would set up the basis for a wide network of remotely accessible documentation. By exploiting the LiDAR sensor equipped on the 2020 11-inch iPad Pro, different apps available on Apple's App Store have been analysed to test their accuracy, as well as their settings customisation to adapt to different CH scenarios located inside or close by the Castello del Valentino in Turin, Italy. From the broad selection of apps on the app store, ten have been subjected to a preliminary test on the small environment of the Cabinet of Golden Flowers located at the Noble floor of the Castle to assess the complexity and customisation of the scanning process, and to declare based on price, sharing possibilities and general model accuracy, which apps can be further analysed on more complex CH scenarios. The scenarios further analysed are the exterior Façade of the Castle on Viale Mattioli, the big and decorated environment of the Hall of Honour on the Noble Floor of the Castle and the Lion lying on the pedestal of the monument to Giuseppe Garibaldi located on Corso Cairoli. For each CH asset documented, the results have been compared with the ones obtained with the Faro Focus 3D X 330, a Terrestrial Laser Scanner used as reference dataset to understand the level of accuracy obtainable from the applications and different acquisition modalities under changing circumstances. From each app, a point cloud model has been extracted and imported on the software Cyclone 3DR and PointCab, for analyses on the level of accuracy with respect to the reference dataset. By analysing the outcomes of this process and by confronting the levels of accuracy with the initial judgment on price, shareability and levels of customisation, it was possible to identify which app and which modality provides the best results and is therefore most suited for an accessible documentation of CH with satisfactory levels of accuracy.