Catching Fire!

If you have teenagers or follow recent movies, then you should recognize that title. Catching Fire, by Suzanne Collins, is the second book in her trilogy: The Hunger Games. The movie version will be released later this year.

And just what in the world does this have to do with LiDAR? Not much at all really, except for the question that it sparks in my mind: What will it take for mobile LiDAR mapping to catch fire and become a widespread tool for 3D mapping? At this point in time, there is no doubt that mobile LiDAR mapping is in its infancy. Systems are few and far between. Mobilization costs are therefore substantial and definitely limit the likelihood of using any mobile mapping system on many projects. In addition most systems are justifiably large, complicated, and expensive.

While mobile mapping is in the early stages of budding, aerial LiDAR has been in full blossom for better than a decade. It is now considered the most cost effective means of 3D surface extraction (although new algorithms want to challenge that). In most cases it has surpassed passive imaging (traditional aerial photogrammetry) on all but the smallest projects.

Since aerial LiDAR systems (ALS) and ground mobile mapping systems (MMS) both rely upon largely the same technologies, one has to wonder what is stunting the growth of MMS. Lets take a look at a few possibilities by studying both aerial and mobile solutions.

ALS has only one single, prominent competitor and that is aerial photogrammetry. MMS has many competitors not just in terms of technologies but service providers as well. While there may be a few hundred aerial photogrammetry firms in the US, there are many thousands of surveying and GIS/mapping companies. There is definitely strength in numbers.

Aerial photogrammetry is by nature expensive because of the platform. A pilot is required along with an approved plane or helicopter and, of course, expensive cameras. While ALS is also expensive, it is not unexpected for photogrammetry firms. A price difference between a camera system and an ALS of 5 to 25% is not earth shattering or unacceptable.

Mobile competitors on the other hand are often under $10k, and almost all are under $30k. To bring a several hundred thousand dollar solution into the same market area is to invite serious criticism from the competition and untold reluctance from potential users. It almost begs that the solution must provide some sort of immeasurable result that cannot otherwise be obtained. Usually this is in regards to safety of human life. Next might be the savings in traffic closures for roadwork (saving millions of dollars to the local economy and possible incidents of road rage).

Weather and time of day are a serious factor with aerial photogrammetry but is much less of a concern with ALS. Rain, snow, and lightning are always a concern but clouds, shadows, and nighttime are of little consequence to ALS. So again, ALS is a welcome solution. Ground surveying can go forward in all types of weather, including rain and snow. MMS is not well suited to precipitation. In addition, a ground survey can locate all buried or slightly buried objects, measure manhole inverts, and get behind fences. MMS is strictly limited to line-of-sight collection.

These are just three reasons the industry has been able to embrace ALS quicker than MMS. In each case, ALS was not just a new technology that might at some point rival the competing methods, it was immediately apparent that for some projects (i.e. 2 foot or greater contour work) it offered a major advantage. State and county projects, along with other small scale projects requiring vast amounts of coverage, were perfectly suited for ALS. This is not to say that ALS was welcomed by all or that it didnt have its share of stumbling blocks, but it definitely has proven to be a worthy solution and was adopted quite quickly by the industry. More than a decade into ALS and the systems still range from $500k to over $1M depending upon performance. Price does not appear to be the limiting factor.

Where does this leave MMS? To begin with MMS does offer a serious advantage in the priceless category of safety. Since all collection is done from the safety and comfort of a vehicle the likelihood of injury or death is almost eliminated almost, but not entirely.

The other major benefit is in regards to traffic outages. This is almost purely economical for the entire community. A busy roadway system can be mapped at traffic speeds, day or night, with or without escort, collecting far more information for later viewing than can be collected by virtually any other means. A traffic outage, even for a few hours on an interstate, can quite literally cost millions of dollars.

There are many, many advantages of using MMS for 3D data collection besides those already mentioned. Nevertheless there are relatively few systems working and available. Why? Is it price, performance, reliability, lack of quality, too much to learn, or what?

Perhaps it is a misconception of what MMS is. We continue to hear people question the cost and the necessity of GPS and IMUs (the latter contributes greatly to the cost). Even the slightest familiarity with terrestrial laser scanning (TSL), or static/tripod scanning, brings the expectation of easy setup, no control required, and millimeter level accuracy everywhere. MMS cannot directly compete in this sense. GPS is required. A suitable IMU is critical. The computation of the trajectory by means of GPS is essential. Whether post processing or using RTK for the trajectory, the operators must have some understanding of GNSS. In addition, they have to concern themselves with GPS outages, meaning they have to execute care in their route selection and distribution of control points.

It could be that the industry expects that a static scanner can be easily converted to a mobile scanner for five or ten thousand dollars. Or that all mobile scanners can achieve 1 to 2 millimeter results. Or provide 400, 800, or 2000 meter range. It might be that expectations are not only for a static and mobile scanner, but a UAV as well. Or possibly a scanner that can map an interstate at super high accuracy (mm) and density (thousands of points per meter), a river bank, a tunnel, a county from an airplane, a historic site from a UAV, underwater, or in a cave…

Ideally wed all like to see the orb from Ridley Scotts movie, Prometheus. I know Ive already had projects where it was the only tool the client would have accepted. Ah, but for the FAA!

The question remains, what will it take for MMS to catch fire and be the next great mapping tool?