uses the data contained in Building Information Models (BIM) to overlay the worksite using augmented reality using mobile devices. This allows different stakeholders involved in the building process such as construction site managers and craftsmen to surveil and closely monitor the construction site as the construction progresses. Errors on the site (e.g. missing openings in walls for the piping) as well as errors in the 3D BIM model can easily be detected and prevented from happening at early stages of the building process. For this, GAMMA AR provides users the functionality to mark errors and make text/photo/voice annotations. These annotations are visible to all involved stakeholders in the app as well as in a central web service. This way the usual manual communication between different stakeholders that occurs at different stages of the construction process is automated and much more efficient. Finding construction errors early is crucial, as costs and time to fix errors can drastically increase if the errors remain undetected, causing need for many expensive adjustments. GAMMA AR therefore yields in not only reduced construction costs but also time savings. Furthermore, GAMMA AR extends its usability even after construction has finished as it helps facility managers in maintaining buildings by providing visualization and communication infrastructure (e.g. visualize cables inside a wall for electricians). Planners and Project Managers can access the data from GAMMA AR in realtime using the GAMMA BIM PORTAL. Here users can manage their projects, distribute files and manage tasks with assignments, due dates and revision states and connect with other solutions