From The Editor: 3D Data Integration

A 737Kb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE

Welcome to the "User Group" edition of LiDAR Magazine. We will be distributing the magazine in June at Riegl LiDAR, and Optech’s ILSC 2013; and then at the "big dog"–the Esri User Conference, the Survey Summit and the new one for me–the 3D Mapping and LiDAR Forum in early July. It’s going to be a busy month.

Let’s start with a quick recap for those of you who did not attend SPAR 2013. Michael Jones the Chief Technology Advocate at Google gave a very disruptive key note presentation which included an offer to pay $1 billion for an underwater scanner that would be suitable for mapping the world’s oceans. Michael is an original thinker and thought leader who sees the world from a different perspective than most of us. I’m glad he is interested in mapping.

The keynote by Prof. (em) Heinz Rther, Principal Investigator of the Zamani Project was also very impressive. His recent article in LiDAR Magazine described the work that he is doing in Africa to document and preserve cultural heritage. Unfortunately this important work may be coming to an end as Prof. Rther explained that his funding is going to run out soon. That would certainly be a loss to all of us. If you have any thoughts on how to help him please let me know.

On the new technology front it seemed that low cost, handheld scanners were quite popular in the SPAR 2013 exhibit hall. These included the ZEB1 from 3D Laser Mapping and from start-up Dot Product 3D a tablet-based, 3D imaging solution for under $5,000. Autodesk had a large presence for the first time as they were launching their ReCap platform strategy. The views of the Rocky Mountains from the Broadmoor were as pretty a site as you could see anywhere.

In case you missed this blog post entitled "Laser Scanning is Not a Luxury!" I want to call your attention to it. Actually this statement comes from Tocci Construction a progressive Boston, Massachusetts firm that is a leader in Building Information Modeling, or BIM. When I see a construction firm make a statement like this I believe it is signaling a major shift in attitude.

Things don’t change all that fast in the construction industry, but when they do the impact is huge. An increase in demand for laser scanning building documentation services was also recently documented by a civil/survey engineering firm that I spoke with. It seems the architects are recognizing the value of investing in documenting the as-found conditions to avoid future change orders–amazing.

The hot topic in this issue of LiDAR News is data integration. Over half the articles have this connection. Leading the charge is the dynamic duo of Meg Waters and Stephen Wilkes (husband and wife) from the Boston area. They are working on above- and below-ground data integration involving laser scanning and groundpenetrating radar (GPR)–a major challenge. Stephen has the laser scanning expertise and Meg the GPR. In their article they argue that there is a significant opportunity and utility in combining subsurface geophysical data with above ground terrestrial scanned data that is not being addressed.

For those not familiar with GPR, from Wikipedia," Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This nondestructive method uses electromagnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR can be used in a variety of media, including rock, soil, ice, fresh water, pavements and structures. It can detect objects, changes in material, and voids and cracks."

I have also been working with the team at H2H from Troy, New York on their integration of above and below the water surface 3D data capture. They have been using a boat outfitted with a multibeam side scan sonar and a MDL laser scanner. Their task was to assess the structural integrity of a series of navigational locks in upstate New York. They had great results from this impressive systems integration effort. Their results will be the subject of a future article.

The third combination of "above and below" 3D data acquisition comes from Karen Richardson. In her article she reports on the use of a bathymetric LiDAR in the Pacific Northwest to characterize stream beds. The ability of LiDAR to penetrate water depends on a number of variables, most importantly water clarity, but as compared to sonar or GPR it would seem that the use of a single sensor would have to make the data integration task significantly easier. However the folks at iLinks, the systems integrator for the H2H boat have certainly streamlined that dual sensor workflow.

One of the key challenges that I see in trying to combine data streams from different sensors is the coordinate system issue. Let’s take the example of documenting a lock using sonar and a terrestrial laser scanner. Merging the data at the interface of the two data sets would require a unified frame of reference that seamlessly ties all the data together.

In the H2H case they use a navigation system that relies on GPS and when the elevations are below sea level they use negative values for Z. This seemed to work perfectly, at least for this example. I would assume the same could apply to bathymetric LiDAR. I am not sure how depth below ground is handled with GPR. Ideally an approach that would support the integration of all 3D data into a single unified model should be the ultimate goal.

On a final note, in Lewis Graham’s Random Points column in this issue he brings up the challenges associated with data generalization. This would certainly apply to bathymetric and below ground data. I am sure the oil exploration industry, who has been dealing with seismic exploration for decades could shed some light on this topic, but as I learned in my Ph.D. research 35 years ago they are notoriously tight lipped when it comes to sharing technology.

As the GIS pros like to say, "It’s all about data." I hope to see you soon at one of the upcoming user conferences.

Gene Roe, LS, PE, PhD
Managing Editor & Co-Founder
LiDAR Magazine

A 737Kb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE