As-built surveys are essential to verify a building’s metric and geometric data during and after its construction. Let’s see in detail what it is!
If you deal with construction, you know that one of the essential tasks in the design process is the survey of the building (as-built survey). Basically, it is the measurement of the building after its construction, along with its and graphic rendering.
A survey has many important purposes and, depending on the objective, it is advisable to choose the relevant type of representation and the adequate tool.
In addition, it is essential to use 3D architectural design software to process the collected data and automatically obtain the BIM model and the drawings (floor plans, elevation views, cross-sections) of the current state.
What is an as-built survey?
An as-built survey is a set of geometric surveys conducted on a building during and after its construction. Its aim is to produce drawings (with 2D and 3D models) that exhaustively describe the consistency of the building at that precise moment. The survey is also used to verify the conformity between the approved project and what has been constructed.
At the end of the verification survey, the as-built model is created. It is then completed and delivered to the client after the construction of the work (but updated as the work proceeds). The result is an information container that combines the 3D model with the data (geometric and not) related to the completed building (technical data sheets, manuals, photographic documentation, etc.).
In general, an as-built model shows the exact position of the structural, mechanical, hydraulic, electrical, and architectural elements to reconstruct a complete picture of the building as is at the time of the survey.
The process of creating an as-built model starts with the geometric survey of the building and the collection of information to be included in the model and ends with the delivery of the BIM model to the client. Essentially, it is the reverse engineering of what usually happens in a traditional BIM workflow in which the 3D model is made to describe the project in detail and support the works to be carried out.
To obtain the 3D as-built model 2 paths can be followed:
- modify the project’s BIM model according to the works actually carried out on site;
- proceed with the acquisition of the geometry of the existing building with special survey tools and techniques (laser scanner, photogrammetry, etc.).
The survey can be carried out with different instruments, from traditional and manual tools, such as measuring tapes, to the most technologically advanced devices (total stations, laser scanners, drones, geoslam, etc.).