3D Scanning: Understanding the Differences In LIDAR, Photogrammetry and Infrared Techniques

It is increasingly important for engineers and scientists to choose the right technique for capturing “reality data” - the physical information about a structure, object, area, or living being. While you can hire a 3D scanning service to do the job for you, this post will focus on hardware and software that you can use to do it yourself.

But what does “3D scanning” mean, anyway, and what options are available to you?

Types of 3D Scanning

3D scanning is the act of mapping an object, structure, or area, and describing it in the form of x, y, and z coordinates - a format known as a “point cloud”. Some of the more unusual forms of 3D scanning include computed tomography scans and ground-penetrating radar, which have fascinating uses in fields like archeology and medicine, but this post will cover three specific ones: digital photogrammetry, white-light structured scanning, and LIDAR - a term which, depending on who you ask, is either a combination of “LIght and RaDAR” or an acronym for “Laser Imaging Detection And Ranging”.

Since it’s unlikely that you have an unlimited budget set aside for 3D scanning, this article will explore a few different technologies and compare both their performance and their costs - you may not have the budget to capture reality data down to the nanometer, but that doesn’t mean there’s no tool you can use to achieve your goal.

1. LIDAR: Sometimes used as an acronym, LIDAR was originally a combination of the words light and radar, and was first used to accurately model clouds following the invention of the laser in the 1960s.

Christian Stallings, R&D manager at McKim & Creed, explains how the real-world accuracy (and cost) of UAVs compares to Traditional Surveying and LiDAR. (Video Courtesy of 3D Robotics).

So that’s 3D scanning in a nutshell. Hopefully, whether you’re a curious novice or an inquisitive expert, you now have the information you need to take your next step. But if you still have a few lingering questions, read on, and we’ll try to clear some of them up.

Which Kind of Scanner is Best For Certain Kinds of Objects?

When it comes to picking the right scanner for your object, the most important factor is size: any given scanner has its own unique field of view, which will determine how much surface area, and how close you need to get for accurate results.

Are Handheld Laser Scanners Always Best for Small Objects That Require Very Detailed 3D Scans?

If you need to measure small objects - for example, screws, transistors, or dental molds - to a high-level of accuracy, you’ll probably be better off with a handheld LIDAR scanner.Many laser scanners have a field of view ranging from approximately four inches to three feet. For larger objects, you can take multiple scans, then stitch them together.

Of course, not everyone can afford their own personal laser scanner, and if you don’t know how to use it, you also have to factor in the cost of training. But while LIDAR may be your best option, that doesn’t mean you don’t have others - photogrammetry and a great camera can be an acceptable substitute even for small objects.

To reiterate, you can get high-quality 3D models of smaller objects with photogrammetry software and a great camera. More on that later.

How Important Are Good Scan Results?

It depends on the type of job you’re doing. Ask yourself - what type of accuracy, resolution, and speed am I looking for?

It goes without saying that no amount of money saved is going to be worth it if your model doesn’t look like, well, your model. If you keep the relative accuracy of different techniques in mind, then you can at least temper your expectations - but that doesn’t mean you should settle for an inaccurate scan. Still, no measurement device is perfect, and not every application requires a highly accurate 3D scan.

The more parts you need to scan, the more important speed becomes. This is even more true if the object is in motion during the scan - it can be difficult to accurately measure something that won’t sit still. In this case, using a fast method is even more important.

Processing speed, software, and workstation quality are all key factors. It is very important to understand the capability of your scanner’s hardware and software when planning your scanning project or workflow. Some scanning engines do more post-processing than others. But as a rule of thumb, the more your hardware does in terms of processing your 3D model, the better.

How Does One Setup a Scanning Workflow?

First, consider the user’s experience. Some scanners are easy to use, and if you’re scanning something like the inside of a house for a real estate listing, you can use a plug-and-play infrared scanning technology like the Matterport 3D Camera, which just requires an app and iPad.

On the other hand, if you need a more sophisticated scanner, and don’t have any experienced users, you’ll need to account for training time when planning a project or workflow. The wider the knowledge gap grows, the more training time you’ll need. This is especially true for commercial LIDAR.

Why Are Commercial 3D Scanners Preferred for Major Industrial Applications?

The simple answer is that they provide better scans in a wider variety of environments. They may be prohibitively expensive for the average individual, but they can capture voluminous point clouds at a rate of over one million points per second!

Jacob Hockett, CEO of Minds Mechanical grew up in the aerospace industry and is widely considered an expert on metrology for aerospace, working regularly with Lockheed Martin, GE, as well as tech giants like Google on some of their moonshot projects. He was responsible for scanning Kapton on the James Webb Telescope for NASA. 

"Kapton is a material that’s going on a spaceship, and is miserable son of a gun to measure, mainly because you can’t touch it.  It’s infrared absorbent, which makes it difficult for light radar systems to measure it.  Technically, only one flight-layer has been measured so far, and the rest will be measured next year.  It’s one of the hardest materials I’ve ever had to measure because its main purpose is to absorb the infrared spectrum from the sun.  If sunlight bounces off of this material it messes up the field of the optical sensors, the data will be screwed up.  The laser radar system was more like a laser tracker.  It takes what’s called a patch measurement, a surface vector intersection. It takes a little patch around the vector, sets a plane through it to make sure nothing is going in or out at a specific range, and you want to come in at around 25 microns."

I had a chance to ask Hockett about the state of 3D scanning in aerospace and metrology, and he said the following:

"3D scanning is great, and it's come a long way. Photogrammetry has always been an industry standard. I treat it slightly different than 3D scanning. But your LIDAR systems, and your white-light/blue-light scanning systems have changed quite a bit. I'm seeing them more on the automation side, than anything else as it relates to quality. The handheld scanners and white-light systems are still not quite as accurate as your high-end systems, which is why they are still blackballed in the aerospace industry."

I also had the chance to speak with Stuart Woods, Vice President, Geospatial Division at Leica Geosystems. "From my standpoint, I think we're on the cusp of really leveraging regularly collected data for multiple applications. I use this sort of funny analogy. It won't be long before my son can order his own 3D world for Call Of Duty based on our neighborhood. For public safety and security, training and so on, the concept of using real-world data sets beyond surveying is what I see as the next big trend, and we are really focused on this. Working in 3D, and working with a point-cloud is becoming democratized, which is very exciting."

Milos Lukac, a 3D Generalist for Reality Capture told me that the company is hyper-focused on all photogrammetry and laser scanning markets, and that their team is dedicated to the task of improving the quality and speed at which 3D models are reconstructed using Reality Capture. He said that he sees a bright future for 3D scanning and digital photogrammetry, and they have a lot of ideas they can't discuss right now that will be implemented in the near future. 

High-end laser scanners are also more efficient at processing the scan data, freeing up post-processing software for more customization and specialization. You can generally view vendor samples of these high-end scans upon request.

How Important Is 3D Scanning to Reverse Engineering?

I recently visited the mechanical engineering department at Virginia Commonwealth University, near my apartment in Richmond, and while I was waiting for the department head, I wandered into the digital fabrication lab and saw two students leaning over display screens, running Creaform handheld scanner software and displaying what looked like a newly scanned brake pad. I asked them what they were working on, and they explained that they had an assignment to reverse engineer and improve the design of a brake pad as a mid-term assignment. 

Recreating design intent with VXmodel scan-to-CAD software module and Autodesk Inventor to have the native CAD model of an automotive part casing. (Video courtesy of Creaform).

3D scanning offers students like these the opportunity to innovate, using handheld LIDAR devices like the HandySCAN 3D from Creaform.

Creaform provides an integrated solution, including both a handheld laser scanner and software that allows students to manipulate and change their scan data. It can be used to scan an object that’s already been designed, like a brake pad, and make improvements to it on the fly in a virtual environment. Needless to say, 3D scanning tools like Creaform are absolutely crucial to reverse engineering.

Now that that’s cleared up, let’s examine some specific examples of 3D scanning technology in detail. 

Free Digital Photogrammetry Options for Mobile Devices

If you’re really on a tight budget, there are plenty of apps that let you capture reality data using hardware you probably already own. Thanks to the ubiquity and miniaturization of camera and sensing technology, the average smartphone user is in possession of a very powerful compute, containing amazing doodads like gyroscopes (for detecting orientation), magnetometers (for detecting magnetic fields), proximity sensors (an infrared LED and light detector), barometers (to measure atmospheric pressure), hygrometers (to measure humidity), thermometers (to measure heat), heart rate monitor sensors (to take your pulse), pedometers (to measure distance traveled), fingerprint sensors, and an increasing amount of haptic (touch-based) technology. With all these tools, you can get surprisingly good 3D scan results using nothing but an iPhone.

Selection of Free 3D Scanning Applications for Mobile Devices

3D scanning hardware for mobile devices (some capital required, USD 79 – 500):

There are other photogrammetry applications for mobile devices that require some external hardware, such as iSense from 3D systems, the Structure Sensor from Occipital and RealSense from Intel. Scandy Pro is also included in this category.

Of course, you could always build a scanner from spare parts, but I’ll address that in a later post. For now, I’ll just assume that you’re interested in trying out 3D scanning, and we’ll cover your options from least expensive to most. 

Selection of Handheld Infrared Scanners

Photogrammetry Software: (Free, Free Trial, Subscription or License):

When it comes to photogrammetry, software like Autodesk’s ReCap and ReMake (formerly Memento/Catch123) are among the best options available for free though there is also open-source software like Skanect, which captures reality data with a Microsoft Kinect. The first full-body scan I ever had was done with a Microsoft Kinect with Skanect mounted on a lazy susan at the Museum of Architecture and Design) in Manhattan, which was taken by 3D printing service Shapeways in late 2014.

When experimenting with photogrammetry, always keep in mind that the quality of the photo counts, and that means the quality of the camera counts, too. Of course, the higher the quality of your photos, the more storage space you’re going to need, so if you’re trying to capture something quickly as a reference model, and quality is not key, then you can always use a lower-quality camera and stitching software like Autodesk’s ReCap as a substitute.

Expensive – Laser Scanners (USD 2000 – 100,000)

LIDAR is the most accurate form of 3D scanning, but also the most expensive, and it requires the most knowledge and experience. But if cost is no object, then laser scanning is the way to go.

If you’re new to lasers, remember that they are lasers! There are some safety classifications that let you know just how much light power you’re dealing with - Class 4 lasers are the most dangerous, but as I’m sure those of you experienced (but hopefully didn’t deliver) a laser pointer to the eyes, even a low power laser can do some serious damage.

How to Classify Lasers:

This is just a short selection of commercial lasers, and they do get very expensive. There just isn’t enough room in this post to go into detail about every existing option, so here is a pretty random selection of what’s available, how much it costs, and what analogous software you can use with each one.

Bottom Line

There is a world of information about 3D scanning, and new applications are being developed every day. Infrared scanning is great as a low-cost entry option for the curious newbie, but in my opinion, photogrammetry provides the most universal opportunity to try 3D scanning, given the sheer ubiquity of cameras If you compare photogrammetry to the amount of technical know-how and cost of LIDAR-based 3D scanners, photogrammetry seems to be the most balanced technology, and I suspect it will continue to be used in new and interesting ways, especially given the expanding power of cloud computing.

Of course, 3D scanning also connects to emerging technologies like mixed reality and virtual reality. If you look at the Occipital Bridge, for example, or SketchFab, the online 3D modeling community that allows you to upload and view your models in virtual reality, the convergence of 3D technologies is clearly continuing on its warbling and sometimes foggy collision course.

Oh, and of course, there’s artificial intelligence, even if the computer programs that currently masquerade as “true artificial intelligence” might be better called “superficial intelligence”.. When AI enters the physical world through robotics and scanning in a way that evolves past what we see today with autonomous cars and the current state of robotics, there’s a lot to keep your eyes moving.

In the meantime, keep on scanning.