Reality capture is an emerging technology in the design, construction, and building ownership industries. While laser scanning is predominantly thought of as being synonymous with reality capture, reality capture encompasses many other technologies as well. Reality capture in the A/E/C/O/FM industry addresses the documentation of the real-world geometry of buildings and their related objects. Such documentation is obviously important for existing structures and historic buildings as a part of documenting their as-built conditions. Equally valid uses of reality capture include documenting new construction and key milestones. For example, this could be using reality capture to document anchor rod placement before structural steel is shipped to the site. Such anchor rod reality capture documentation could be vital for confirming key interface geometry and alignment of steel base plates with the anchor rods cast into the concrete. Other examples include documenting the square footage of buildings for architects or owners who are considering renovating, providing a tenant finish out with new construction, or space accounting for the management, leasing, or sale of the property. Additionally, reality capture addresses issues such as documenting sub grade utilities or structural reinforcing and concrete. Other forms of reality capture might include measurements that are to a conceptual level of accuracy for creating mass models for general building layout and design during a schematic design phase. The following is a brief introduction to these dimensional data capturing technologies as concepts to be considered for anyone looking at writing and updating their BIM Execution Plans. Such technologies include, but are not limited to:
- LiDAR (laser scanning)
- Photogrammetry
- Drones and UAV
- Ground Penetrating Radar (GPR)
- Ultrasound rebar scanning
- Distance meter and traditional building documentation
- Robotic total station surveying
- Thermal imaging
- Augmented Reality Technology
- Point Layout with points in the field, GPS data collector
An overview of reality capture technologies that owners should be aware of when considering their BIM Execution Plans is provided below.
1. LiDAR (Laser Scanning)
Laser scanning is a technology that is used to capture the surface shape of an object by combining its laser beam scanning and distance measuring capabilities to accurately and instantaneously document data. Multiple scans from various viewpoints are collected and can be compiled to form a 2D/3D model.
2. Photogrammetry
Photogrammetry is a tool that takes photographs and derives measurements from them. Its’ use of high-speed photography and remote-control sensors enable the visualization of spaces from realistic perspectives, oftentimes augmented to provide square footage measurements or to serve as a supplementary walk-through visualization. (Think: Google’s “street view” feature.)
3. Drones and UAV
An unmanned aerial vehicle, or UAV, is an aircraft (or “drone”) without a human pilot aboard. Commonly utilized for their ability to capture content from a bird’s eye view, UAV usage in the building industry is versatile – whether it’s safety/security monitoring, documenting jobsite conditions and progress, capturing aerial photos, or planning project sequence – UAVs are a cost-effective and emerging technology.
4. Ground Penetrating Radar (GPR) & Ultrasound Rebar Scanning
Both GPR and Rebar Scanning utilize subsurface radar technology to detect reflected signals from subgrade content within a structure. Using nonintrusive electromagnetic waves, these technologies provide a range of possibilities:
- GPR is typically utilized as a preventative method within the construction and related industries to avoid mistakes and safety hazards associated with cutting into an object with hidden elements (i.e., a concrete slab) or digging underground where subgrade systems may be installed (i.e., electrical cable).
- Ultrasound Rebar Scanning is a method used to locate and verify the placement, thickness, or variance of subgrade elements within a concrete slab. Types of on-site testing may include slab thickness verification, PT cables, steel reinforcement, or determining the location of other MEP systems up to 18” subsurface.
5. Distance Meter and Traditional Building Documentation
Distance meters are laser rangefinders which use a single laser beam to measure the distance to a singular object. Thought of as an alternative to the tape measure, distance meters are a simple but accurate tool that can help users avoid measurement discrepancies.
6. Robotic Total Station Surveying
A total station is an electronic tool used for surveying and measuring in the construction and related industries. With a robotic total station, the operator is able to use the instrument with a remote control from a distance; as opposed to nonrobotic total station, which would require an additional operator. The tool also includes an internal computer which, in partnership with strategically placed targets or prisms, can collect data and perform calculations. Measuring abilities include vertical and horizontal angles as well as slope and triangulation.
7. Thermal Imaging
Thermal imaging is a technology that detects radiation and produces images of it: regardless of illumination or visibility. Commonly used by soldiers, thermal imaging allows for the visualization of variances in temperature. In the construction industry specifically, this tool can be used to detect faulty insulation or prevent impending system failures by allowing technicians to identify heat leaks in a nonintrusive manner.
8. Virtual Reality and Augmented Reality Technology
Virtual reality (VR) is an interactive computer-generated experience that takes place within a simulated environment and incorporates auditory and/or visual feedback. Augmented reality systems may also be considered a form of VR that layers virtual information over a live camera feed into a device that gives the user the ability to view 3D images. A person using virtual reality equipment is able to “look around” the artificial world, move around in it, and interact with virtual features or items.
Augmented reality is used to enhance natural environments or situations and offer perceptually enriched experiences. With the help of advanced AR technologies (e.g. adding computer vision and object recognition), the information about the surrounding world of the user becomes interactive and digitally maneuverable. Information about the environment and its objects is overlaid on the real world.
9. Photo Imagery
Photo Imagery is a building documentation process that utilizes 360 degree and High Dynamic Range (HDR) cameras to document different stages of development, building conditions for pre-construction planning, final as-built documentation for turnover or downstream modeling, milestone capture, and utility/in-slab/above ceiling/ in-wall capture for overlay. This non-measurement-based portion of photographic reality capture is often included in a construction project’s general conditions and requirements.
Sources for numbered list:
https://en.wikipedia.org/wiki/Laser_scanning; https://en.wikipedia.org/wiki/Photogrammetry; https://en.wikipedia.org/wiki/Unmanned_aerial_vehicle; https://www.sciencedirect.com/science/article/pii/S1877705817330461; https://en.wikipedia.org/wiki/Ground-penetrating_radar; https://www.proceq.com/compare/rebar-detection-and-cover-measurement/; https://en.wikipedia.org/wiki/Laser_rangefinder; https://en.wikipedia.org/wiki/Total_station; https://en.wikipedia.org/wiki/Thermography; https://en.wikipedia.org/wiki/Virtual_reality; https://en.wikipedia.org/wiki/Augmented_reality
