Scan to BIM is a process which converts the data acquired from laser scans into 3D BIM Models with all the details and components of existing structures. Downstream applications for Scan to BIM Services today are used for the creation of as-built documentation, project renovations or fit-out works. The step by step planning and detail that can be conveyed by BIM models generated from point cloud data can also augment the on-site construction process and improve the functioning of the building at any point in its lifecycle.
Looking at the importance and widespread application of Scan to BIM it is important to follow a structured process which allows to reap maximum benefits. Below we highlight the five steps of Scan to BIM process:
1. Defining the Scope of Work:
Before jumping into the point cloud to BIM process it is important to determine the purpose, the level of detail required and the budget. This sets the tone for the whole project. The purpose of the project refers to whether it is for as-built documentation, for partial or complete refurbishment or to keep track on progress of an already ongoing construction. It is also to be considered if there is an already present documentation or 2D Drawings which need to be updated or cross-checked.
Once the purpose is defined it becomes easy to determine what building elements need to be scanned and modelled and what would be the LOD. Higher the LOD, more is the level of accuracy of the BIM model. Though, it also means that the cost goes higher. Here an appropriate balance needs to be made between cost and level of detail required. Finally, only by defining scope of work and budget right from the start, the actual scanning and modelling can run efficiently.
2. Choice of Equipment:
Once the SOW is clearly defined the next step is choosing the right equipment. The right scanning device or a combination of devices can be done by carefully understanding the LOD required and the type of the project. For example, if any infrastructure corridor has to be scanned like railways or roads here mobile laser scanners can be more beneficial than a terrestrial laser scanner. Even when it comes to 3D laser scanners there are many choices in the market each with its own unique blend of features in terms of accuracy, portability, speed, and setup time like Faro, Leica, Trimble etc.
3. The Scanning:
The next step comes on-site where the data is to be captured. Ideally, while scanning a building laser scanners are attached to standard tripods. These lasers rotate at high speed and as laser beams fall on different solid objects, their position is recorded as “points”. These points are clubbed together to create an accurate 3D representation of the space. Greater the number of points collected, higher is the level of accuracy. Laser scan collect data on million points in one second, so the high volumes of data can be collected in short intervals of time. High-resolution cameras can be attached to the scanners to take images of site simultaneously with the laser scan.
Laser scanners can also be mounted on land-based vehicles like cars, trans or airborne vehicles such as UAVs, helicopters or even boats. Another way to get information is through time of flight scans or phase based scans.
4. Registration Process:
Registration is an important step in Scan to BIM process to optimize the data obtained from the 3D Scans. The scanning process is also not always conducted from one vantage point so the registration process stiches the images together to get a clear picture of the building. The scans need to be stitched together to get a clear picture of the building. There are various registration methods which can be used like planes, targets, cloud to cloud etc. Here, 360 degree pictures which were taken can be used as a reference to register the scanned data.
5. 3D Modelling:
The final and the most crucial step is to create a 3D model from the data. Depending on the project requirements and sow there can be a need for collaboration between different disciplines like MEP BIM, Architectural BIM and Structural BIM Services. The model has to also be embedded with information about the construction materials, current quality and condition of the component, cost etc. Clash Detection also needs to be run to check for any interferences when it comes to refurbishment or restoration.
The modelling approach also varies based on the available information. For instance, when there is an already as-designed BIM available and Scan to BIM is being conducted to update it. Here the scan data is aligned with as-designed BIM to get an updated BIM. Since, the creation of an updated BIM or as-built BIM is the main motive, 3D modelling is an extremely crucial step. It is only on the basis of that any construction will take place.
The design derived from scan to BIM is more reliable. It saves on time, reduces waste and minimizes errors. Scan to BIM also facilitates transparency, better communication, and fosters collaboration. This five-prong process of Scan to BIM provides the accurate data which is needed to ensure smooth reconstruction, facility management or creation of accurate documentation.
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