The 3D Digital Survey Revolution

After 40 years in the surveying/mapping business, I am amazed at how digital technology has changed our profession and how the pace of change continues to accelerate, particularly in the area of 3D imaging and measurement.

The first computer that I could afford when I was starting my surveying business in the mid-1970s was the Texas Instrument 55 handheld calculatorthats mine in the photo. I lost all my work when I turned it off, but it was still a great time-saver over the traditional log tables.

Compare that to todays mobile scanning systems that collect centimeter-level accurate 3D data from a vehicle traveling 60 miles per hournow thats a lot of change. Each time I think that there just cant be another technical breakthrough of this magnitude, then along comes the next one.

For instance, most of us thought that nothing would top GPS (global positioning system) technology, but I believe 3D imaging systems could have as great an impact on the surveying/mapping profession and, if you include the short-range metrology world, maybe even greater. I think this is particularly true if you look at the post-survey utility of the data, which, after all, is the purpose of making the measurement in the first place. Three-dimensional images can become permanent visual records of the as found conditions.

I am concerned that many surveyors may be thinking that laser scanning and other 3D imaging technologies are not tools that they need to master, that they are just too exotic for the small surveying practice. To me that sounds similar to the response our profession had to other disruptive technologies like GIS (geographic information system) and GPS. And now laser scanning.

Not the same, you say? Maybe. But can you afford to sit on the sidelines while others establish a first-to-market advantage? Laser scanning may not cause a revolution, but evolution is much too passive a term for the changes occurring now. What if a tripod-mounted scanner was similar in price to a total station? That is the price point that the tripod-based scanner manufacturers are trying to achieve in the next few years.

Lets see if I can convince you that we really are at the beginning of the 3D Survey Revolution and that this is your call to arms.

3D Surveying Technologies and Methods
To build a strong case, I really wanted to state that the laser scanner is the first instrument that allowed the surveyor to measure in 3D, but when I thought about that for awhile, I began to question that position.

For instance, I remember performing hundreds of 3D topo surveys using the stadia method. From some quick online research, it seems that the stadia method of surveying has been around for at least a couple hundred years.

In case you are not familiar with stadia, you can obtain the distance, horizontal direction, and difference in elevation from the height of the instrument, so you can compute X, Y, and Z. Now combine this with the plane table (I am old, but I have never used a plane table on the job) and perhaps you have the first 3D (well, maybe 2.5D) mapping system. It was point by point, but when you were done you had a field-verified, topographic map, usually of pretty high quality.

Then I thought about GPS, or perhaps more correctly GNSS (global navigation satellite systems). Most of us believe that satellite navigation has caused a revolution in our profession and that these systems support 3D. I guess I couldnt disagree, but I would counter that although you are locating a point on the face of the earth, its just not the same as scanning a scene in 3D. Its the difference between determining your location and performing a survey of the as-found conditionsin other words, passive versus active.

Taking this into account, perhaps a more qualified position would be that the laser scanner is the first optical, digital instrument that can be used to directly measure in 3D. That is why I think it is fair to say that the laser scanner is certainly a disruptive technology (see American Surveyor, April 2007) with the potential to create revolutionary change in not only the surveying and mapping industry, but many others that are directly and indirectly related.

To better understand its impact on the grassroots surveying/mapping profession, lets take a look at each of the major platforms where laser scanning is being used today.

Aerial Platforms
In the 70s, if you had a project of 50 acres or more that required detailed topography and planimetrics, and you had four to six months depending on the time of the year, you would contract with a photogrammetry firm and hope that it would deliver on time. There were also issues with areas where conifer stands prevented the photogrammetrist from seeing the ground, and with obtaining the required ground control.

Over the years digital photography has almost completely replaced film, and the need for ground control has been significantly reduced, thanks to GNSS and inertial. However, many of the inherent limitations of a passive, camera-based system such as season, time of day, sky condition, and ground cover remain with aerial photogrammetric mapping methods.

Enter LiDAR (Light Detection and Ranging), with its ability to capture data at night if necessary. Since it uses an active laser-pulsed sensor, not only can it find the ground even in dense tree cover, it can provide very accurate height and surface model information for all of the objects in the coverage. Not only can you get the topography, or bare earth model as it is called, but you can also derive other surface models, such as tree canopy and rooftops.

Most aerial LiDAR data is provided in the LAS format. ASPRS (American Society of Photogrammetry and Remote Sensing)currently manages this format, which supports several standard data classes. By requesting a classified LAS file as the deliverable, a surveying firm can create a number of valuable products for its customers by exploiting the 3D point cloud images.

Instead of having to rely on an aerial mapping firm to post process the data into a 2D map with planimetrics and perhaps 3D contours, the surveyor can extract all of this information from the point cloud with the appropriate software and expertise, perhaps on an as-needed basis. The surveyor is also able to offer customers intelligent 3D models (more on this later) built from the point clouds, rather than 2D CAD objects.

At the national scale, countries around the world are beginning to make investments in LiDAR data sets. In the United States plans are being discussed to produce a nationwide LiDAR data set with 1 meter spacing.

Several other exciting 3D aerial imaging technologies are also beginning to emerge. These include the use of oblique photography and IFSAR (Interferometric Synthetic Aperture Radar). Discussion of these is outside the scope of this article.

Have you ever used a tripod-mounted laser scanner? The most important field skill required is to stay out of the scan area, or you will become part of the permanent record.

This brings us to perhaps the most important reason for the surveyor to care about 3D imaging, particularly when it applies to capturing data that might be covered by the professional licensing laws for the projects jurisdiction.

The surveying decision-making paradigm is shifting from the field to the office, and that is where the problems can arise. A skilled party chief, who spent many years learning what it means to be close enough, or as Bob Seeger wondered, what to leave in, what to leave out, is now potentially being replaced by the office technician.

Theres no question that the use of laser scanners can improve safety, increase productivity, eliminate trips back to the field, and provide 3D information that is virtually impossible to obtain by any other survey method, such as the clearance of a power transmission cable over a 10 lane highway, but the critical decision-making process is shifting from the field to the office.

At this time it does not appear that laser scanning is going to be applied to boundary surveying, but what about the case of 3D cadastres? The latter is just beginning to be considered for the high-rise property ownership issue models prevalent in many rapidly growing urban environments around the world.

The point here is not to look at this as a turf war but as an opportunity to expand our sphere of influence and offerings to our customers. One of the most important uses for laser scanning is in process plants. I doubt most of us think of these firms as potential customers, but who knows more about making these kinds of measurement-based decisions? Using a tripod-mounted, surveying instrument to record the as-found conditionsthat is our world. This is our opportunity to seize.

The hot 3D imaging platform is mobile. This is where the scanner, and usually a number of other sensors, is mounted on a moving vehicle, sometimes on an elevated frame to increase visibility, and then driven at speeds up to 60 miles per hour. Applications include highway, urban canyon, and rail. Tunnels are best handled with this method.

Reduction of the raw sensor data requires a high degree of sophistication, similar to that found with aerial. Once a georeferenced point cloud has been derived, a trained surveying professional can use that data to produce the deliverables required for design, 3D mapping, and asset management.

Mobile is going to become the preferred platform for many infrastructure mapping applications, since it can acquire data rapidly, without the problems associated with a flyover. Becoming involved with this technology at this early stage can result in a competitive advantage.

Intelligent Infrastructure Modeling
The significant value add in the 3D imaging workflows comes in transforming 3D georeferenced point clouds into intelligent 3D models of our urban and rural infrastructure. This is the real challenge currently facing this industry, given the inability of most of the leading CAD and GIS graphics engines to handle the extremely large file sizes associated with point cloud data. These systems were originally designed to automate the 2D drafting and mapping manual procedures, not to support the viewing and interrogation of hundreds of millions of 3D georeferenced points.

The software component of the 3D imaging market is playing catch-up. Scanners are dumb. They collect millions of points when a few hundred might do, but that is the price one pays to get everything the first timein 3D. And the trend from the hardware side is up: collecting more points at a faster rate.

The surveyor has an opportunity to get in on the ground floor of the growing movement to use point clouds as a shell in which professionals integrate GIS, CAD, and other databases to form an intelligent, 3D infrastructure model. In fact, we surveyors can become the recognized experts in this growing field as cities around the world clamor to replace 2D master plans and expensive physical models with these digital cities. And you do not have to own a tripod scanner to be in this business, let alone an aerial or mobile platform (remember the real surveying is done in the office). The data collection can be subcontracted. In fact the actual scanning operation is rapidly becoming a commodity in some markets, because that is not where the real value is derived.

Converting a point cloud into an infrastructure model that can be directly accessed by a customers design, asset management, and 3D mapping software of choice is the goal. It is going to take a few years for the major software vendors to provide all of the necessary tools, but in the meantime we need to begin to invest.

A Long Runway
As we all know, real estate development runs in cycles. The average surveyor needs to diversify. There are many opportunities to apply our expertise in making 3D measurements. One of the most exciting opportunities involves laser scanning.

As we have seen before with other disruptive technologies, the surveying profession has a choice. We can start a debate or turf war, or we can invest in the technology and be part of the solution.

Its a new world, a 3D digital imaging world, and its changing at an accelerating pace. The younger generation will not accept anything less. They grew up with it. This may be the technology that attracts the younger generation to the profession.

As surveyors, lets not miss the revolution.

About the Author:
Gene V. Roe has a Ph.D. in civil engineering. He is a licensed land surveyor and professional engineer. He has worked in academia, consulting and the software industry. At the time he wrote this, he was the Autodesk Surveying and Mapping Product Manager for Map 3D.

Please note that the opinions expressed in this article are those of Mr.Roe and not necessarily those of Autodesk, Inc.