System Development of an Augmented Reality On-site BIM Viewer Based on the Integration of SLAM and BLE Indoor Positioning

Traditionally, when an engineer wants to use Building Information Model (BIM) on-site to support tasks for construction or maintenance, the common approach is to use a tablet or a notebook to run a BIM viewer, thus requiring manual operation for model manipulation. In addition, the BIM presented through the screen and the actual on-site visual are in two separated views, and thus the two are less likely to be synchronized. Augmented Reality (AR) superimposes virtual objects or information that can be interacted with onto real world images or videos. Therefore, this study applied AR to superimpose BIM with an indoor industrial environment for a more immediate and intuitive integration of the physical site and BIM. At present, most applications of combined BIM with AR uses marker or marker-less image recognition to superimpose virtual content using feature points of the marker or object image as an identifier. If the identifier moves outside the device camera view, the virtual content will not appear. With advances in AR, a new AR mode is introduced in this study based on simultaneous localization and mapping (SLAM). Based on this technology, the virtual BIM is placed based on the device's understanding of the environment and then superimposed onto real objects in the scene without any identifiers. A manual method is proposed to align a chosen BIM component to a corresponding real object. Based on the alignment, the system calculates the angle and position to accurately superimpose the BIM on the virtual environment, with these locating characteristics recorded for future use. Since the load and display of an entire BIM model is not necessary and is inefficient in the context of indoor AR applications, the model is divided into room models, and the system only overlays the corresponding room model for a specific room. This is achieved through a combination with the Bluetooth Low Energy (BLE) indoor positioning technology, so that the room in which the user is located can be immediately identified and the corresponding room model can be loaded.