Augmented Reality (AR) technologies allow computer-generated content to be superimposed over a live camera view of the real world. Although AR is still a very promising technology, currently only a few commercial applications for industrial purposes exploit the potential of adding contextual content to real scenarios. Most of AR applications are oriented to fields such as education or entertainment, where the requirements in terms of repeatability, fault tolerance, reliability and safety are low. Different visualization devices, tracking methods and interaction techniques are described in the literature, establishing a classification between Indoor and Outdoor AR systems. On the one hand, the most common AR developments correspond to Indoor AR systems where environment conditions can be easily controlled. In these systems, AR applications have been oriented traditionally to the visualization of 3D models using markers. On the other hand, outdoor AR developments must face additional difficulties such as the variation on lighting conditions, moving or new objects within the scene, large scale tracking, etc… which hinder the development of new systems in real scenarios.
Although AR technologies could be used as a visual aid to guide current processes in building construction as well as inspection tasks in the execution of construction projects, the special features involving construction site environments must be taken into account. Construction environments can be considered as especially difficult outdoor AR scenarios for several reasons: structures change frequently, additional structures (scaffolding or cranes) cover several visual elements during the simulation, every technological part (sensors, wearable computers, hand-held devices) can be easily broken, etc. For this reason, although the capability of AR technologies in construction site environments is a hot-topic research, very few developments have been presented in this area beyond of laboratory studies or ad-hoc prototypes.
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