Laser scanner technology is evolving rapidly, and there’s a device for just about every 3D modeling job you might face. As scanning technology improves along accuracy, cost and scan time dimensions, their platforms are becoming increasingly varied and more dynamic. Here’s a quick roundup of the most common types of scanner platforms on the market today for as-built modeling projects.
Stationary Scanners for High Accuracy
Ideal for: Large area, high accuracy
Stationary (a.k.a. static) scanners are used in the majority of scan-to-model projects today. They yield very accurate results because 1) the laser isn’t moving (very much) between bursts and 2) they’re easily tied into surveyed control points. The scanner and platform must be repositioned within the space to gain a complete image of the targeted area.
For interior projects, they must be set up and moved from room to room, and often they must be set up on multiple points within a complex space, like a plant room, to scan behind equipment or around corners.
Upside: Most accurate results. Most reliable method of scanning for engineer-grade survey data collection
Downside: Each scan results in a separate point cloud file. Registering point clouds is a science (and art) unto itself. You’ll need to execute many scans to cover the entire space. Repeated setup, scanning, and disassembly can become taxing.
Tip: Time-of-flight scanning is usually used outside or for large interior spaces where the scan radius approaches exceeds 200-300 feet. For areas smaller than that, phase-based scanning is preferred for its speed and accuracy at shorter ranges.
Handheld Laser Scanner for Small Spaces
Ideal for: Small Spaces, short ranges
Often used to complement static scanners, handheld devices fit into tight spaces behind equipment and in the ceiling plenum. Their accuracy is very high when scanning distances of less than 20 feet. Their platform is typically a modified mobile computing device or a manufactured scanning device. Most handhelds utilize Simultaneous Localization and Mapping (SLAM) technology that captures successive depth-measuring images, referencing the location of each point in one frame to the same point in the previous frame.
Upside: Low cost, easy to use, fast and accurate at short ranges. Because they’re designed to maneuver around smaller spaces, they are ideal for quickly scanning all sides of smaller, complex spaces like mechanical rooms. Great for those places where your larger stationary scanner can’t reach.
Downside: Limited range: could you imagine walking the entire length of pipe runs for 10 hours a day? Plus, the SLAM-based approach typically employed with this type of technology has a tendency to cause the point cloud to “drift” as you capture larger areas. As each frame is registered to the previous frame, positional errors stack on top of each other with distance. It is not unusual to find data that is several inches away from truth after about 50 feet of scanning.
Tip: The use of SLAM technology means that the imagery is typically registered on the fly while the device is moving. The units capture data very quickly over small areas, are relatively easy to use and typically cost much less than static scanners.
Mobile Scanners for Speed
For the sake of brevity, we’ll limit our discussion of mobile scanner platforms to wearable and dolly-mounted units (apologies to our airborne and marine platform friends). Although not as accurate as static devices, mobile scanners collect data from many different viewpoints much faster.
There are lots of benefits to attaching a laser scanner to a something as mobile as a person or dolly. For starters, you’ll be able to scan a project much faster since you’re not worrying about setting up the tripod, scanning, moving and repeating. In a sense, these can be deployed anywhere you can wheel (or walk) it.
Ideal for: Speed, large occluded spaces
These are generally deployed for large areas, including outdoors, where speed is a necessity. These devices often rely on SLAM, inertial measurement unit (IMU), and Global Positioning System (GPS) technologies to register their collected point clouds to a survey network.
Upside: Fewer (contiguous) scans. Registered in real-time. Mobility means much less setup and breakdown time.
Downside: Mobile scanner platforms aren’t as mature as the stationary platform alternative. Movement introduces accuracy degradation.
Tip: The dolly mount is slightly more stable and accurate than the backpack. Both remain relatively expensive due to their newness in the market.
Scanner technology is advancing at a very rapid pace. Yay! When you’re determining the best platform for your next project or investment, keep in mind that there’s still a correlation between fixing the scan location and increased accuracy. Keep your eyes peeled though – advancements in IMU, GPS and SLAM (and even the combination of the three) are happening…fast.