In my first column, Survey/CAD/GIS Integration – It’s About Time!, posted back in November 2007, I peeked into the crystal ball and wishfully saw a future where we would have a three-way integration of GIS, CAD and survey data for seamless “field to finish” solutions. I’m still very keen on that topic, but these days, when people ask me to peer into the crystal ball, I’m seeing several key technology trends on my “must watch list”. Near the top is the emergence of laser scanners, which I think will ultimately push GPS out as the most popular way for surveyors to manage field data.
For this quarter’s column, I’ll start by sharing a few tutorial basics on laser scanning for readers new to the topic, covering forms of laser gear out there, field work benefits, cost issues and other considerations. Next I’ll offer my thoughts regarding where we are on the evolutionary path to widespread adoption of scanners, followed by a call for the use of a standardized file format for point cloud data gathered by laser scanners. And be sure to check out the set of audio podcasts featuring John Brown of Metco Services. In the series John offers advice for those considering the jump to laser scanners and a case history involving the use of laser surveying combined with the use of AutoCAD Civil 3D software.
Laser Scanning Basics
I realize that many of you reading this column are currently using GPS technology to gather point data from the field. Here’s what you need to know if you’re getting ready to make the jump to laser technology-based scanners for field data collection. There are basically two forms of laser systems available today. Some are airborne systems (LIDAR) designed to be mounted on aircraft. As the airplane flies over a zone the laser can capture millions of points in the blink of an eye that can then be used to generate very accurate terrain models.
The other category of laser scanners for surveying are the 3D terrestrial, tripod mounted models. As with their aerial cousins, these units can also quickly and very accurately gather amazing amounts of point data. Ground-based lasers are rapidly gaining in popularity for a host of applications including terrain modeling, forensic investigation, and historic preservation. And, of course, they are also being used by Hollywood to scan a site and rapidly create a 3D model that can then be used in an animation of movie special effects sequence. At the end of this column I’ve provided a set of links to see a variety of laser scanners.
Scanners Rock but Carry a Big Price Tag
Use a laser scanner for field point gathering one time, and you’ll never want to go back to GPS. Laser scanning eliminates the need for a traditional rod man/woman. And it affords the luxury and safety of being able to set up your tripod virtually anywhere on the site. Use GPS to survey a busy four-way intersection and you know that you’ll have to deploy someone out in high traffic areas with a range pole or prism. With a laser scanner mounted on a tripod you can set up on a sidewalk, turn it on and let it bounce light off every surface it sees to create a huge set of fixed reference points (a.k.a., a “point cloud”).
You might be thinking, “What about moving vehicles and/or pedestrians?“ No problem. The post processing software typically provided by the scanner manufacturer can weed out all the “noise” or false reflections to produce a very accurate point cloud. Basically, the software identifies all static points and washes out variables. Scanners also save gobs of time in the field. In seconds you can capture hundreds of thousands of points. Compare that to the GPS method where it’s a process of clicking off points based on distance increments of so many feet or seconds per click.
The bottom line, comparing laser scanners to GPS is like comparing apples to elephants in terms of the volume of data you can generate in a very short time. So what’s the downside? It’s simple, cost. The 3D terrestrial laser scanner units I’ve worked with cost between $100,000 to $200,000 each. And then you’ve got to factor in maintenance and update packages that can add $10,000 to $15,000 per year.
Opportunities and Challenges Ahead
There are four opportunities/challenges I see impacting the further deployment of laser scanners on a widespread basis within the surveying community. They include :
• The challenge of dealing with huge data volumes
• Easily moving point data from the scanner’s post processing software into civil engineering CAD programs
• The need for our industry to settle on a standard file format to expedite this data flow
• A cool opportunity for someone to develop an application to let you view point clouds on the web
Size does matter!
Point cloud data gathered by a laser scanner can represent gigabytes and gigabytess of information. Mainstream desktop PCs and laptops aren’t designed for this level of data capacity. So, you’ll have to build or buy a very beefy PC with huge mass storage. Once you accommodate the massive data you then encounter the challenge of getting this large volume of point cloud data to play nice with your CAD software. Point cloud files can bring just about any CAD application to its knees.
Most applications specifically designed to get point cloud data into a CAD application use some form of a reference file or demand loading to thin out the points in the cloud to fine tune exactly what you need for terrain modeling or “as building”, etc. The key challenge for CAD software developers is how to quickly take raw point cloud information, weed it out to such a state that accurate terrain models or just models in general can be made from it. Stay tuned, a lot of bright software developers are working on this problem now.
File Unity – Is LandXML the Answer?
The point cloud thinning and manipulation software laser scanner manufacturers provide typically can output field gathered data as traditional ASCII text, DWG or XYZ point files. Some of these applications also generate line work as well. All of these file formats offer a path for importing point cloud data into a civil engineering design package. For example, I’ve used Leica scanners and the Cyclone software provided with the unit to manipulate field point data and import it into AutoCAD Civil 3D. I’ve used, in this model, a combination of two file formats – Field Book (.fbk extension) files generated by a sub-application within Cyclone called “Virtual Surveyor” and ASCII text. It works, but I’d like to see the process become much, much smoother.
What’s a better path? As laser scanning gains in popularity I think our industry needs to settle on a standard for the native raw format. And to my knowledge, universal agreement on a single file format is still wanting. One solution might be for the developers of scanner software packages to adopt LandXML (see www.landxml.org). After all, LandXML has been accepted as an industry standard in the past few years and may be the logical choice for being able to facilitate point cloud data sharing. I’d like to know what you think. Should we start a campaign?
Web-Delivered Point Clouds
On the GIS side, and this is shared on the CAD side as well, there’s an emerging opportunity to develop applications where the point clouds could be viewed via the web to foster greater multi-team collaboration. Cyark (see www.cyark.org), for example has a point cloud web viewer, and I think this is a move in the right direction. I realize that this approach involves figuring out how to deal with the sheer volume of data that point clouds represent. Pushing that volume of data over the web is a daunting challenge to say the least. But as bandwidth increases (e.g. fiber optics) and our computer power keeps going up (I’m now seeing pro-sumer eight-core PCs coming to market) it’s every more entering the realm of feasibility.
LIDAR and/or terrestrial 3D laser scanning represent the future of survey data acquisition. For all of us, from architects and surveyors to engineers and construction professionals, the shift from GPS to laser scanning for surveying is inevitable.
Laser Scanner Makers to check out include :
• Leica Geosystems at www.leica-geosystems.com
• Trimble at www.trimble.com/spatialimaging.shtml
• Riegl at www.rieglusa.com
• Optech at www.optech.ca/prodilris.htm
• Z&F (Zoller & Frohlich) at www.zf-laser.com/e_index.html
• 3D Digital Corp at www.3ddigitalcorp.com/index2.htm