By: Laura Diaz- Riegl USA Marketing Manager
The topic of full waveform analysis and online waveform analysis is a prevalent one when it comes to Riegl’s work. Not having come from a technical background, I had a lot of catching up to do when I joined the Riegl USA team. Full waveform was a concept that I understood the benefits of, but had not yet figured out why it worked. That all changed today.
As Riegl USA prepared to present and exhibit at the recent SPAR Conference in Denver, I found myself searching for the answers to the questions I was inevitably going to be asked while representing the company in booth 28 in the Hyatt Regency Exhibit Hall.
To educate myself I sought the council of Riegl USA’s own Engineering Support Manager, Vladimir Kadatskiy. We began this informal interview with Vlad explaining the difference between Online Waveform and Full Waveform. Allow me to explain the information bestowed upon me (in my own words).
The LMS-Q560 and the LMS-Q680 are airborne full waveform scanners that operate offline. While the VQ-Series, which includes the VQ-480, the VQ-180, the VQ-250 and the VZ-400 are online waveform scanners.
What does “online” waveform mean Vlad?
Real-time digital signaling processing with multiple returns per shot capability. The number of returns you receive from a single laser shot is dependent on the environment. In scans involving dense vegetation, you can expect more returns than indoor scanning.
What does this mean for the user?
With unlimited returns comes great detail,for example, specification regarding vegetation and accuracy when measuring slopes. If you have the option to choose how you post-process, you can customize processing specifically for your application. That means getting things done exactly how you need them done.
What about online waveform analysis?
Online waveform analysis gives you multiple (not unlimited) returns and immediate results. As you scan you can see the data! The multiple returns provide great data with more detail and increased accuracy.
How do online and full waveform analysis work?
Digital analysis of the waveform allows the user to define the way the target range is calculated in post processing. Echo-digitization reveals all of the laser pulses, which results in details of the depth distribution of targets in the path of the beam.
What type of applications are a good fit for waveform analysis?
Because of the versatility of the full and online scanners that Riegl manufactures they are great for a variety of applications including, but not limited to:
- high resolution mapping of urban areas
- high accuracy flood-plain mapping
- corridor mapping
Why would you choose one over the other?
It is completely dependent on your application. What is more important for your project? Do you need to save time? Would you prefer to avoid having to purchase additional software? Online Waveform may be right for you! However, if it’s important that you have a completely customized experience and the most detail that you could possible squeeze out of a scanner, you probably want to post process offline. Are you still not sure which one suits your project best? Contact Us.
How are Riegl’s online and full waveform scanners different from a conventional laser scanner?
Traditional Lidar imaging systems output the 3D coordinates of surface locations hit by the laser pulse. They typically provide 2 to 5 returns. Pulse Detection method has significant impact on accuracy and causes a reduction in quality of measurements. Conventional systems depend on range output which, alone, does not contain information about structures or sloped surfaces.
Think of shining a beam of light on a flat, smooth surface. You will find that the beam hits the surface and a perfect circle is displayed. But what happens when you shine that same light at an angle, or into a corner? Distortion ensues! If you’re trying to capture information about the entire corner at which you aimed the beam, but can only choose one point, which point do you choose? That one point could not accurately measure the change in depth where the walls meet to create a corner. With online or full waveform you can save all of the points and therefore capture what is actually going on. With waveform analysis data is more complete.
Allow me to recap
Full and Online waveform analysis give the user:
- high quality data that is low in noise and high in resolution.
- vegetation detail
- surface features (e.g. slope)
- Unlimited (or multiple) returns
Do you have more questions about full or online waveform analysis? Do you have something to add? Or can you help me further clarify? Post in the comments!