The Basics of MEP 3D Scanning: Point Clouds and BIM Models
Increasingly MEP Contractors involved in renovation and/or refit projects are looking for solutions that will enable them to quickly and effectively digitally represent the as-built environment as a 3D BIM model with associated BIM data.
So how do you create a 3D BIM model using scanning methods?
The creation of a BIM model using building scanning methods is a two stage process:
- Firstly scan the site using a 3D Scanner to create a point cloud
- Secondly analyze and process the point cloud and produce your 3D Model
How do you generate an MEP site scan?
This is the faster, and easier step in the process. Essentially you place your 3D Scanner on a stable surface within the site and, using the device interface, start the scanning process. The scanner will fire a laser around the space identifying key features and recording their coordinates. Once the laser has finished capturing data points all the recorded data points are available for use in a single electronic file. This is known as a point cloud.
What is a point cloud?
A point cloud is a set of data points in a three-dimensional coordination system created by a 3D scanner. Normally a standard X, Y and Z system is used and the coordinates generated by the scanner will represent the external surfaces of the items scanned.
When purchasing a scanner you will want to consider various important factors. You will need a high accuracy output to create the sort of models required by MEP contractors. You will also want to consider the weight and mobility of the device, ease of use and potential for ROI.
How do you analyze and process the point cloud and produce your 3D Model?
Many contractors new to creating BIM models using 3D scanning techniques wrongly think that the majority of the work is done during the 3D scanning phase. This is not the case. As we have seen, 3D scanners create point clouds, nothing more, nothing less. These point clouds must now be turned into the BIM models we need to output using point cloud processing software.
The quality of the models you produce and the speed with which you produce them will be dependent in part on your selection of high-quality point cloud processing and analysis software. Many contractors choose to make survey notes to accompany a scan and inform 3D Model Production.
How do you produce the model?
The model is built up manually by repeatedly selecting sets of points from the point cloud that correspond to individual 3D elements and then converting them to geometry.
To begin to create a 3D element you select a section of the point cloud to model and create a segment to work within. The segment you select needs to contain all the points that are relevant to the geometry you are going to create e.g. pipe.
Next, you select the type of geometry you are going to apply to the segment you have just selected and use the tools within your point cloud modelling software to build up the geometry for this item. This activity is repeated until all required elements of the building are modeled.
Good point cloud modeling software will contain functionality that allows you to duplicate geometry across your model, meaning you only need to model repeated items once. It will also contain tools that speed up the creation of common MEP items. Trimble RealWorks allows you to automatically model a pipe by selecting a section of the pipe data in the point cloud and then extrude the section along the point cloud. The extract function will create a pipe that follows bends in the point cloud.
Is it worth the effort?
MEP Contractors elect to use 3D scanning technologies to generate BIM models for a variety of reasons including reduction of cost of model creation, deskilling of model generation activities, cost reduction and quality improvements and as the basis for a client O&M manual and FM information For more information on the benefits of using 3D Scanning methods to create a BIM model see our blog post Field to BIM MEP: What and why?.
For companies early in their journey with 3D Scanning and BIM model generation, it may be preferable to work with a company who can create your 3D BIM models for you. Look for a company who will work with all your available documentation, including construction plans, models, fabrication standards and/or and/or MEP system specification to build up your model. Also look for a company who will provide you with the BIM LOD (Level of Detail) that you require in your model.
Trimble offers both 3D Scanning and point cloud processing software to support you and your team as you begin to use BIM methodologies on renovation and refit projects.
Trimble RealWorks is specifically designed for point cloud processing and analysis. It provides a complete solution to efficiently register, analyze, model and create deliverables using data from virtually any point cloud source.
The Trimble TX8 Laser Scanner is an efficient 3D scanner that captures high-resolution data.
Trimble also offers a 3D Modeling from Point Cloud Service will create a 3D model of your projects mechanical or electrical systems based on the specificity required.