HoloLens 2 Spatial Mapping Capabilities in Vast Monumental Heritage Environments

HoloLens 2 is a state-of-the-art of Mixed Reality device that can augment the natural environment with virtual content in the form of holograms. Spatial mapping is the capability of the device to scan the environment and provide the user with a detailed 3D mesh model representation of its surroundings. The device can place holograms about real-world objects, perform occlusions and simulate physical interactions only having the geometric knowledge of its operating environment. HoloLens 2 mapping capabilities have been extensively tested. Nevertheless, no test was performed on monumental heritage buildings, where dimensions far exceed the typical sensor working range of the device. The authors want to evaluate the capability of the device to map monumental spaces. In these environments, dimensions, repetition of elements and heterogeneity of areas provide a real challenge for out-of-the-box Microsoft localization and mapping algorithms. The test case will be Milan Cathedral, inside the research project to build an MR application to help and enhance the systematic and planned maintenance intervention and inspections. Mapping capabilities have been tested in very different spaces: i) the south nave; ii) the empty volumes between the internal vaults and the external roof ("Sordine"); iii) the narrow spiral staircase connecting the south nave with the roofs lower level.