One of the technologies considered central to smart construction, the digital twin, simply means building a 3D model in a virtual world that is identical to reality. By applying georeferencing technology to point clouds, one of the outputs of drone mapping, you can obtain a highly accurate 3D model map, and this becomes the foundation of a digital twin.
This may sound a little complicated! Below, let's take a closer look at what a point cloud is, what georeferencing is, and how 3D models are actually used on construction sites!
A 3D point cloud is a collection of countless points that hold coordinate (x, y, z), color, and height information in three-dimensional space. Visualizing the terrain, structures, and equipment of a construction site as a point cloud makes measurement and analysis easier and enables precise site management.
Point clouds can be generated in two main ways. The first is to use sensors such as LiDAR or RGB-D, and the second is to use 2D images captured by a drone.
On construction sites, the drone photogrammetry method is widely adopted because of its cost efficiency and ease of use. The core principle is to photograph the work site from various angles and then overlap and align the captured images to reconstruct them in 3D. For more detailed information on LiDAR and the photogrammetry method, please refer to this article.
So why is georeferencing necessary for a point cloud? It is easier to understand if you think of the 3D model made from a point cloud as a work drawing drawn on paper, and georeferencing as the scale bar drawn beneath that work drawing.
Georeferencing refers to the process of assigning coordinate values to point cloud data. By adding location information to point cloud data through georeferencing, you can generate a 3D model that fits the exact scale of the site.
Georeferencing requires a GCP (Ground Control Point). A GCP is a landmark installed at a geographically known location. It serves to accurately determine the position of images, and during drone surveying it allows images to be aligned more precisely using GCPs.
By combining the point cloud data obtained through this process with the GCP data, you can assign coordinate values to the point cloud data. Meissa recommends surveying four or more GCP points to build an accurate model.
The Meissa platform supports a variety of smart construction features through 3D models. With surveying functions such as 'Add location,' 'Add line segment,' and 'Add height,' along with the ability to compare planned-elevation and current-elevation data, you can carry out many tasks that help the construction site without having to visit it in person.
Through 3D point clouds, you can understand the terrain, elevation, and structures of the work site in three dimensions, allowing you to efficiently carry out construction planning, safety management, and quality management.
Cloud-based 3D maps provide intuitive visual information, helping stakeholders such as team members, managers, and clients easily understand the site situation.
It can be used for project management, such as tracking material movement and schedule management, and at Meissa we continue our research so that process progress can be checked quantitatively through point cloud data aligned with BIM files.
You can find more detailed stories about on-site applications in the Meissa Construction Use Case Collection.
At Meissa, we are continuing our research so that the 3D point clouds of on-site data can be aligned with BIM files to check process progress as quantitative figures. To deliver smart construction technology that is genuinely useful on real sites, Meissa will continue to advance its convenience and effectiveness across many areas.
