**4. Augmented reality in BIM**

In the context of augmented reality and BIM we can define augmented reality can as system in which BIM model is used to augment real environment. An AR enhanced BIM modeler could also be envisioned where BIM model information is edited in an AR environment. AR is currently being considered by scholars and practitioners in the area of knowledge, as a "New Age" of information through advanced technology due to the positive effects of its technological potential that its

#### *Using Augmented Reality in Different BIM Workflows DOI: http://dx.doi.org/10.5772/intechopen.99336*

correct use offers to the construction industry, especially in the construction phase, providing significantly affects the efficiency of projects, quality, health and safety [16], and consequently the project cost and duration, positively [17].

In Section 2. we already established BIM as a type of a "central hub" to all data and information related to a specific projects – this of course includes 3D models necessary for AR applications as well as non-geometrical information that could also be linked and accessed in AR applications.

But combining real world objects with virtual ones can be challenging. Researchers Bajura M and Neumann U [18] identified four main challenges to be addressed: (1) the origin of the tracking system is not aligned with the world coordinate system; (2) the transformation from source to object is not accurate; (3) the position of the virtual camera is not correct – usually related to inertial and motion-based sensors errors; and (4) virtual camera-to-image mapping does not accurately model the real camera.

To organize the data processing steps for the final BIM visualization in AR, Williams et al. [19] describes a generalized three step workflow (similar architecture is also proposed by Meža et al. [20]): (1) First, it is necessary to generate geospatial properties for each BIM object where mobile AR application uses geolocation to identify the user's position and, consequently, be able to produce information related to the viewed object; (2) Second, from the moment that the information displayed in mobile AR refers to a user's position, several points surveyed within BIM also need to be identified. These points will represent where users can stay in a physical location and perform mobile AR tasks with BIM data sets related to that location; and (3) Third, for BIM to be usable in a general mobile AR environment, the geometry and property data set needs to be separated into two exchange formats.
