Since the commissioning of the building on the 20th of April 2013, the Rock Cathedral in Lekki, Lagos, has been a tourist attraction. The massive structure has hosted weekly tours of its outstanding facilities and welcomes over 14,000 Christian worshippers every Sunday at full capacity (plus overflow). Apart from the main 10,000-seater auditorium, there are multi-purpose halls, a 500-seater Prayer Chapel, a Gymnasium, a Cafeteria/Restaurant that seats over 200 persons, two recording studios, several offices, a fully functional clinic, and other facilities.
The building is roofed at different levels. The roofs were made from long span aluminum roofing sheets placed on concrete slabs and laid to slope. The roof decks are concealed from view with a concrete fascia, and the main entrance is celebrated with a polycarbonate barrel vault covering. There are also four security posts, and a Service Yard comprising 4 large generator bays, a water treatment facility, a sewage treatment facility and a Facility Management office with sleeping quarters. The main building goes up to four floors, and the parking lots can take up to 1,343 cars (excluding off-road parking), including disabled parking spaces.
Thanks to BIM, this architectural edifice now exists permanently in a virtual database. The client (HOUSE ON THE ROCK) approached ATO Architects in 2018 to do complete as-built documentation of its facilities. This was done to provide a more realistic dataset to guide their in-house facility management team and showcase parts of the building with potential for further development.
The building was originally designed by ACCL Architects and the client provided us with the detailed design drawings available in their archives. We then used scan-to-BIM technology to document the 32000sqm Cathedral sitting on a land area of about 3 hectares. We generated a point cloud model with about 8.3 million points or 30MB Point cloud data using Autodesk Recap, which captured every single detail of the building’s exterior. The point cloud then served as virtual reference material for a detailed BIM Model in Revit from which space, walls, door, window, and curtain wall schedules were automatically extracted.
Using a DJI Mavic Pro drone, about a hundred photographs of the building were taken from strategic points around it’s perimeter. In less than 30 minutes, the images had been captured, and we exported them into the photogrammetry application (Recap) for processing in the cloud.
The reality capture for the exterior of the building was processed seamlessly. However, a challenge presented itself when it came to documenting the main auditorium. It was easy enough to confirm the smaller spatial dimensions using laser measuring tools, but the height and depth of the main auditorium exceeded the distance limits on the device. Also, with photogrammetry, limitations presented themselves in the form of walls with no distinguishable features, windows/glass surfaces, and reflective surfaces. We used the drone inside the auditorium (after safety measures had been implemented) to capture images for the photogrammetry. The results of the interior model were not as good as that of the exterior, but the measurements taken from the model were still accurate enough to provide a firm basis for the Revit model, supplemented by measurements taken on-site on smaller references.
A project of this size needed multiple people accessing it at the same time, and so worksets needed to be created at the start of the project, with the project team collaborating real-time over our local server.
Scan-vs-BIM Comparison
Our mission was to automate the as-built documentation to the very best of our ability and we were impressed with the results, accompanied by a series of lessons learned and opportunities for improvement in future projects identified. A full documentation report with schedules and 3D visualizations were handed over to the client. There is still room for improvement in the full lifecycle management of buildings using BIM, but this experience revealed just how much is possible once we can lean into the BIM methodology. In the future, we hope to be able to move the point cloud model into a VR environment where people can partake in 360 virtual tours of the Cathedral.
As we strive to be the leading providers of environmental design solutions in West Africa, leveraging BIM technology is at the core of our execution strategy. We look forward to collaborating with partners who share our drive and enthusiasm to do more with technology within and outside the AEC industry. We are grateful to the client, HOUSE ON THE ROCK, for the remarkable opportunity.
