3 types of terrestrial laser scanners
According to a recent report from Future Market Insights, the market for 3D scanners is projected to increase fourfold in the next ten years, giving an annual rate of 14%. This growth is being fueled by a variety of industries adopting 3D scanning. From prototyping to quality assurance, 3D scanning is becoming an integral part of the construction, industrial and manufacturing industries.
3D scanners are becoming both more complex and simpler to use. Selecting the right 3D scanner for a particular job is not a simple matter. First off, you need to think about the ranges involved. Simply put, there are three main categories to consider:
- Short-range (for detail and accuracy)
- Medium-range (up to several hundred metres)
- Long-range (hundreds of metres to kilometres)
But the criteria doesn't stop there. You need to think about level of detail, capture of colour, scan speeds, mobility, size of data sets generated, and more. Fundamentally, not every scanner will be right for every job.
Although it’s important to think about the individual capabilities of a specific scanner, most scanners do fall into one of three main types, each of which has a set of distinct characteristics. Here, we are going to explore these types to help you improve your understanding of terrestrial laser scanners and their uses.
Pro tip: The software you use is just as important, if not more important, than the scanner itself. Perhaps think about starting at the deliverables you wish to achieve and work back from there? What might look like the best scanner, might come bundled with the most difficult workflow to achieve your deliverable! So choosing a scanner based on the right workflow really could give you the best competitive advantage and faster ROI. For more details, check out our free ebook — The Complete Guide to Laser Scanning Software.
Type 1: Fixed laser scanners
The go-to choice of scanning hardware is this traditional terrestrial laser scanner. This scanner type achieves high-quality output produced from accurate measurement data. Workhorse scanners like the Faro Focus, Z+F Imager 5016 or the Leica RTC360 are great examples of this category.
Traditionally, these devices are set up at various locations with artificial targets placed appropriately for the relative position of scans to be registered. However, modern algorithms allow these scanners to be used effectively with targetless registration, speeding up the process without damaging post-scan registration times or the accuracy of outputs.
Suggested reading: The most popular laser scanners for creating point clouds.
How to use this scanner type
A fixed laser scan survey is a fast and accurate way of capturing the spatial detail of an existing building in 3D. Surveyors use high tech HD laser scanners to capture this information. Applications are wide-ranging, including Land Survey, Mining, As-Built Surveying, Architecture, Archaeology, Monitoring, Civil Engineering and City Modelling. Construction design teams can use laser scanning surveys to capture the precise geometric data for their project models, which once created can be used to facilitate the BIM process.
Depending on your software choices, you will need to pick between using registration targets and a targetless approach to scanning. Manual placement increases the challenge and time-cost of scanning. However, only with the right registration software can quick and effective outputs be created with a targetless strategy. Automated and targetless registration algorithms also open the door to far more effective use of the cloud for registration — again, accelerating outcomes.
Suggested reading: To learn more about algorithm changes and the use of the cloud for registration, check out our free ebook — Are You Ready for the Cloud? A Surveyor's Guide to the Future of 3D Laser Scanning.
Type 2: GNSS-guided mobile scanning
For large-scale point cloud acquisition, mobile laser scanning (MLS) is now commonplace. A typical mobile LiDAR system consists of one or more laser scanners mounted on a vehicle. The trajectory of the vehicle is determined using Global Navigation Satellite Systems (GNSS) and a high-grade Inertial Measurement Unit (IMU).
Often a wheel rotation sensor is added to obtain odometry data. Such systems have been commercially available for several years and can achieve an accuracy of a few tens of millimetres. Their advantage is the rapid acquisition of higher data volumes and coverage of large areas in a small amount of time.
How to use this scanner type
These scanners are ideally suited for applications outdoors, scanning data from platforms, such as boats, trains and vehicles. This type of system cannot be directly used for indoor applications. This is largely due to their reliance on GNSS which is not possible within a building. Also, the increased cost of high-grade IMU in these systems can be prohibitive.
Type 3: SLAM and IMMS
Indoor Mobile Mapping Systems (IMMS) seeks to take the mobile flexibility of GNSS systems and apply it in scenarios where GNSS strength is too weak to operate — generally speaking, indoors. This promises to dramatically accelerate scanning. But it’s also the category of scanner that relies on the least mature technology — and delivers the least precise results.
IMMS are similar to vehicle-based mobile mapping systems. The key difference is in positioning. As GNSS is unobtainable inside, other methods are necessary for positioning where there is no clear sky view. Simultaneous Localisation and Mapping (SLAM), is the most prominent option.
SLAM is an algorithmic attempt to build a map of an unknown environment while simultaneously navigating that environment using the map. It’s commonly applied in autonomous robotics, and is increasingly being used with a surveying context with wearable, mobile scanning technology.
SLAM pulls on inputs from a wide range of sensor types — using both relative position and absolute positioning measurements. SLAM data can be incorporated into broader surveying workflows, and layered on other types of reality capture data. As SLAM becomes a more integrated part of workflows, there will be a growing number of possibilities for how SLAM can be used.
Brands like GeoSlam, Paracosm and NavVis have scanners on the market now. And some Z+F and Faro static scanners already incorporate accelerometers and compasses, and Leica's RTC360 static scanner uses full visual SLAM (they call it VIS) between static scans to aid with rough alignment.
How to use this scanner type
SLAM automates a process that would usually require surveyors to reposition static scanners every time they move to a different position. Although SLAM scans have a reputation for being “rough-and-ready” — lacking the precision of fixed LiDAR — it should be recognised that not every scan needs to be done to the same level of accuracy.
Carrying out scans faster opens up new opportunities for data capture, it's about using the right scanning technology for the right project. Surveyors should look out for more SLAM devices coming on the market as this technology becomes more widely available and used. Combined with the ease of transferring to BIM, 3D LiDAR SLAM might finally deliver a method to capture and analyse sites at speed — quickly and efficiently.
The important thing about using SLAM is to make sure it’s applied specifically where the precision of a static scanner is not needed, and that you have the software on hand to integrate mobile scanning data sets with border reality capture outputs to create full scene coverage with the right level of detail where it’s needed.
Suggested reading: If you want to learn more about mobile scanning, and how to incorporate SLAM outputs with broader reality capture data sets, check out our free ebook — How SLAM Enables the Evolution of Wearable Reality Capture Technology.
The future is being defined by cloud, BIM and automation
There will always be requirements for static 3D laser scanners and for expert surveyors to achieve high accuracy. But the need for rapid 3D maps and models independent of the environment — outside, inside, daylight or darkness — is driving the uptake of mobile scanning technologies.
In future, new hardware scanning devices will have to fit into the digital world of BIM and cloud-based processing. Scanners must be integrated along with other reality capture tools into a wider range of workflows to increase the value of scan data to all stakeholders.
Vercator Software is already delivering the benefits of faster data production associated with mobile scanning systems and brings them to a terrestrial scanning workflow. These include the use of the scene itself for registration, removing the need for targets in the field, as well as cloud-based automated registration.
Surveyors need to be aware of new devices and new cloud-based developments as this will bring about major cultural and process changes. A great deal rests on the ability to manage this technological transformation. If you’d like to know more, check out our free ebook — Are You Ready for the Cloud?