Laser Scanner or Imager? Analysing their Unique Features

When it comes to measuring and surveying tasks, there's no one-size-fits-all solution. The right tool for the job depends on various factors, including the specific requirements of the project, the desired level of accuracy, and the deliverables needed.  

In this article, we’ll explain the key differences between laser scanners and imagers. We'll use a practical example by comparing two popular and innovative products within the Leica Geosystems’ reality capture portfolio: the Leica BLK360 and Leica BLK3D. 

While technologically different, laser scanners and imagers are complementary technologies. A successful surveyor will use both. 

So, what are the key technological differences, what deliverables can I expect, and which one should I choose for the job? 

 

Laser scanner vs imager: what are the technological differences? 

Laser scanners and imagers are distinguished primarily by how they capture reality.  

Laser scanners operate using LiDAR (Light Detection and Ranging) technology, which involves emitting laser pulses from a sensor mounted on a platform, typically a tripod or a vehicle, or a handheld device.  

In contrast, imagers are camera systems that rely on photogrammetry: a technique that interprets spatial information from photographic images captured from the ground or the air using drones. 

 

 

So, how does a laser scanner work? 

A laser scanner uses a rotating mirror which directs a laser pulse in a systematic pattern. When a laser pulse hits an object, it reflects back towards the scanner, which measures the time it takes for each pulse to travel to the object and back. This so-called “time-of-flight” data is used to calculate the distance to the object based on the speed of light. 

Modern laser scanners take thousands of readings per second – the Leica BLK360, for example, emits 680,000 lasers per second. This allows the scanner to capture a dense grid of distance measurements and generate a highly accurate 3D point cloud of the scanned surroundings. 

With dedicated software, point cloud data can be transformed into valuable insights and practical applications across various industries, from surveying to virtual reality and heritage preservation. Therefore, laser scanners are ideal for producing 3D models, floorplans, BIM models and virtual tours. 

 

 

What are the benefits of using a laser scanner such as the BLK360? 

The main benefit is the speed and the time saved in the field. The Leica BLK360 is the fastest imaging laser scanner on the market, capturing a full scan with spherical images in 20 seconds. With the addition of Visual Inertial System (VIS) technology, scans are automatically combined to ensure datasets are complete before leaving the site. That means never going back to the site to repeat a scan or collect more measurements!  

In addition, with the use of the Leica Cyclone FIELD 360 mobile app, the user can control the scanner from their tablet or smartphone while also getting a complete overview and control of the work done in the field. For example, you can see a preview of the point cloud, check if there are shadow cones, repeat the data acquisition if needed or delete the data to reduce the file size. It is also possible to add different types of geotags to enrich the data with useful information. This helps drastically reduce the time spent on site and increases the overall quality of the data. 

 

 

So, how does an imager work? 

An imager works differently from a laser scanner. While a laser scanner actively emits light and measures its return time, an imager captures stereo images of the same scene from slightly different perspectives and turns them into measurable 3D images. This works similarly to how our brains perceive depth through using two eyes rather than one.  

An imager is usually equipped with two or more cameras that will simultaneously capture two or more images of the same scene. Imagers like the BLK3D are equipped with two cameras, and the capturing process is no different from taking a picture with a smartphone. Users can decide to capture only one pair of stereo images (single shot) or several pairs (multi-shot). This choice will have an impact on the accuracy of the measurements – with multi-shot being more accurate. The onboard software will then identify common features of these images and give the user a measurable 3D image. 

 

 

What can I do with the images? 

The user can then extract dimensions from the 3D imager. For example, if the user captured a building facade, they can later extract dimensions, such as the height, width, and depth of a balcony. 

In the case of the Leica BLK3D, the two cameras are calibrated. That means that the distance between the two cameras is known to the system and the 3D image produced is already scaled. So, the user can measure directly in the picture without adding any scale or reference measurements.  

 

 

And what are the benefits of using an imager like the BLK3D? 

A 3D imager like the BLK3D drastically reduces the time spent on-site when making estimations. Typically, construction companies pick the BLK3D when they need to do a preliminary inspection of an existing building, for example for a renovation project. During this first inspection, they need to extract measurements quickly to provide a quotation to their customers and plan how much material they need. In this context, the BLK3D is used in the field to capture images, and the measurements are extracted later in the office using the BLK3D Desktop software. 

The big selling point is that the BLK3D can take accurate measurements quickly. With just a few millimetres of error for indoor applications and a few centimetres for outdoor applications, this is usually accurate enough for estimations. Compared to traditional, non-digital measurement methods (like a distance metre or tape), the BLK3D is much faster, while also being extremely user-friendly. 

Another benefit of imagers like the BLK3D is that they can take measurements that traditional methods cannot. For example, how do you measure the height of a building without a roof overhang? With a BLK3D you can, just from a picture. 


 

So, how do you choose between an imager and laser scanner? 

The decision to use one instead of the other depends on the project requirements and the deliverables needed. Imagers and laser scanners are complementary technologies: each has its strengths, so users should choose the most appropriate tool for a given situation. 

Successful professionals from architects to utility companies have both an imager and a laser scanner in their toolkit and choose to use one or the other depending on the output needed and the phase of the project they are facing. 

To give you a practical example, the BLK3D is perfect for estimations when working on renovation or construction projects for small building interiors or facades up to four stories. It’s a great companion when you need to document the current status or quickly extract dimensions in the field. The BLK3D also allows you to export measurements directly in CAD format and continue to work efficiently from the office. It’s a great solution for anyone approaching the word of reality capture for the first time. 

For larger projects and buildings, working with point clouds can drastically reduce the time spent measuring and documenting. The BLK360, thanks to its ease of use and compact dimensions, is also a perfect solution if you have no previous experience with laser scanning. From the point cloud, it is possible to measure dimensions with high levels of accuracy (4mm at 10m distance). You can also transform the data into accurate 3D models that can be used as a foundation for design, construction, and analysis, or serve as a digital record. It’s a great companion if your goal is to improve your efficiency on the field and take your deliverables to the next level. 

 

Learn more about the BLK360 and the BLK3D here.