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Home arrow Archives   The American Surveyor     

Driving the Islands Print E-mail
Written by Larry Trojak   
Friday, 23 September 2011

A 1.519Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

When the Public Works department for Washington state's San Juan County was challenged with identifying and mapping roadside assets in an effort to improve traffic safety, it responded by sending out crews with hand-held GPS units. They quickly realized both the scope such a project entailed and the overall inefficiency of using that technique. Knowing the importance of the effort, however, the department looked for an alternative approach to gathering that data and found it in a mobile scanning/mapping rental offered by the PPI Group (Portland, OR). Today, every county road on the four main islands which comprise San Juan County, has been driven, scanned and mapped using an IP-S2 3D Mobile Mapping System from Topcon Positioning Systems, resulting in a Geo-referenced 3D file in which objects can be identified, logged, manipulated and measured. And, while the initial intent was more than fulfilled, additional uses for the resultant scan were quickly identified, with new ones arising seemingly daily.

A TIP for Safety
In rural areas such as San Juan County, the threat to motorists generally comes not from running into other vehicles, but rather from driving off the road, hitting roadside structures such as trees, ditches, etc. As part of a Transportation Improvement Program (TIP), the county was awarded a grant to make improvements to increase highway safety countywide. However, according to Greg Sutherland, the county's Public Works GIS Coordinator, they first needed to provide some very basic information.

"As it pertained to public works," he says, "the grant was essentially to eliminate potential roadside hazards. For us, that includes adding or improving our guardrails and signage, replacing signs with poor reflectivity, analyzing road curves with an incorrect pitch, too-steep embankments, trees that are too close to roadways, etc. But, before we could get to that point, we had to provide info such as: how many signs do we have? Where are they located? Do we know what the reflectivity of each sign is? Can we verify the trees that are a hazard, etc.? When we said we didn't have any of these data sets available, we were asked how long it would take to get such data together."

To answer that, he says they did a pilot project on San Juan Island in which they tracked all the signage using field crews carrying handheld GPS units. They found out it not only took a long time, it also exposed workers to unnecessary risk. This, he felt, was simply not the way to approach the problem.

Rubber Meets the Road
In a bit of synchronicity, at about that same time, Sutherland and his people at Public Works had become aware of mobile mapping system that the PPI Group and Topcon were putting together. Intrigued, he explored the concept more and realized that it could be the answer they needed.

"But while we became increasingly excited by the idea, we were also a bit skeptical. After all, how could we be sure it would do all they said it would? So I posed a challenge to Richard Hill, my contact at PPI, to come up and show us. He accepted and we set to work mapping out a short route-about 7.5 miles of road, some rural and some in the town of Friday Harbor-for him to drive with the system."

He says that Hill came up to San Juan Island on a morning ferry, set up a Topcon GR-3 base station and, at about 10 a.m., began the scanning session using PPI's IP-S2-equipped Toyota Prius.

"He drove the route, post-processed the data over lunch and met with us at 1:00 p.m.," says Sutherland. "At that meeting, we were already able to display data and extract features out of it. We were just blown away; absolutely floored. That sealed the deal for us."

Sharing in the Wealth
Having everyone in San Juan Public Works convinced that mobile mapping was the approach they needed to take was simply the first hurdle to overcome. In fact, says Sutherland, getting the concept through the politics of county government was really the hardest part of the entire project.

"It's a newer technology, so we had to educate many people--both those who were writing the grant and those receiving it--as to what it did and what they could get out of it in the long-term. At the same time, we felt that as long as we were moving forward, we should try to get others involved. So we sent out a broadcast email of sorts to the Town of Friday Harbor; the Ports, which encompasses the airports for both Orcas and San Juan islands; utilities like Opalco (Orcas Power and Light Cooperative); Eastsound Water Users Association; Eastsound Sewer District; essentially anyone we could think of."

According to Sutherland, the message in Public Works' email was simple: "When the project is done, the data will be here. If you will want to mine it, you need to go out now and tag your particular assets." Tagging could include anything from painting marks on a pavement, to setting flags, to advance mowing/brush cutting.

"We actually didn't even have a payment arrangement worked out with these other groups at the time," he says. "We were more concerned about making the data available to those who could really benefit from it. By the time we were ready to go, a decent number of entities on all four islands were on board."

Getting to Work
With a route of all of SJC's 286 miles of roads laid out and marked on maps, Sutherland joined Richard Hill and Collin McCoy, PPI's Equipment Sales Manager, to begin driving the route. Work began on a Monday morning on Orcas Island with setup of a Topcon GR-3 base station, followed by a static alignment of the IP-S2.

"With those two preliminary steps done, we were ready to begin driving," says Hill. "The Topcon system we are using is multifaceted: in addition to the three LiDAR scanners which give us a high-res 3D point cloud of everything we encounter as we drive, we also have a 360-degree digital camera which is shooting six pictures every three meters. Each of those six-picture blasts will be stitched together in post-processing to produce a spherical street level-type photo."

The scanners to which Hill refers are positioned to scan the road surface as well as adjacent buildings and other structures up to 30 meters away from the vehicle (Topcon also offers a high definition model unit that scans 1.3 million points at 100m range). In the IP-S2 unit itself-also mounted as part of the instrument package on the Prius' roof-multiple sensors determine the vehicle's position and attitude on a real-time basis, while a dual-frequency GNSS receiver tracks both GPS and GLONASS signals for optimum coverage. Accuracy is further enhanced through use of vehicle wheel encoders. Retrofitted to the vehicle's rear wheel axles, each encoder detects the rotation of its respective wheel. By comparing the difference in rotational speeds between the two wheels, the vehicle's attitude can be more accurately computed.

Driven to Succeed
The project for SJC involved about 60 hours of driving/scanning and, by project's end, roughly 1.2 terabytes of data was collected. Post-processing of that data was done using Topcon's Geoclean software which handles the GNSSbased vehicle positioning, integrates that GNSS data with data from the IP-S2's Inertial Measurement Unit, then combines imagery and scanned data to generate full-color point clouds. In SJC's case, the data was also post-processed against that from the GR-3 base for even higher accuracy.

While Sutherland's initial estimate of 286 miles of county roads held true, the actual miles driven were more than double that.

"When you factor in all the dead end roads and the routing needed to ensure complete coverage, we actually logged well over 600 miles," says Sutherland. "That also included some scanning of non-county assets such as the Port of Friday Harbor (airport and marina), the airport on Orcas Island and the Town of Friday Harbor itself."

He says they could not have been more pleased with the end product and the system's ability to provide them with the tools they needed for the road safety project. "The end goal of all this is, of course, safer roads. But key to the whole effort is the fact that we no longer have to send road crews out to collect data on guard rails, then do it again for striping, then do it again for pavement ratings, and so on. And every time we look at this data we see additional elements we can capture. For example, during the drive, the noxious weed Scotch Broom was in full bloom and showed up really well; making it easier for us to deal with. We can also more easily measure the height of specific structures such as the overhead arch at Moran State Park; that's an added benefit. And I'd also like to think that this can serve as something of an informal historical record; a snapshot in time of our islands. I'm really proud of that."

Value-Added Info
Sutherland feels that the project did not end with the post-processing of the data, nor did it end with their own use of the data in its various forms. Instead, he says their effort has generated a good deal of interest from others outside Public Works-interest that continues today.

"There are a lot of people looking at what we've done and seeing how it can benefit them," he says "For example, we have gotten a pretty firm commitment from our E-911 coordinator because they can appreciate the value of the data in emergency situations. They see that, when people call in to report a fire in a specific location, they can immediately dispatch the engine, then look at the data and see where the hydrants are located, how far those hydrants are to the structure-even know what type of structure it is. There is a real benefit in giving their responders more advance information rather than having them just roll up blind. This data set lets them do that."

PPI's Collin McCoy says they've been using the IP-S2 since February of 2010 and were, in fact, one of the first Topcon dealers to have one, start working with it and establish a workflow based on it.

"One of PPI's business models is to focus on the cutting edge technology and scanning definitely falls into that category, so it seemed a good fit for us," he says. "At the time, Topcon was focusing its IP-S2 efforts more on the GIS market while we were looking at adopting the tool to the survey and mapping community. But there is currently a lot of crossover between those two industries: GIS people are looking for tighter data and survey people are looking for ways to diversify their business. So this is the perfect tool to provide a lot of data in a very concise, accurate, usable format. And, as more and more third-party companies provide mapping solutions such as feature recognition and auto data extraction, I have no doubt that usage of the technology will just continue to grow in popularity."

Excellent Foresight
In light of the SJC mapping/scanning project's success, Sutherland says he is extremely grateful for how well things went, and adds that it could not have happened without the hard work of everyone at Public Works but cites one man in particular.

"This project almost died on a number of occasions because many people were unsure of what it would produce, others wanted to demand additional studies, some felt it would eliminate their jobs, and so on. But Jon Shannon, our Public Works director, went to the mat repeatedly to make certain those questions were addressed and the project got done. He convinced the naysayers that we should be doing it because it is the smart thing to do-and not just for the department but for the residents of the county. He said that, if you want to maximize your tax dollars, here's a great way to do that. Yes, we will spend money up front, but the return on investment is so compelling in the long-term, we simply have to do it. Well, he could not have been more right and, based on what we're seeing so far, it looks as if we will continue to reap the benefits of that decision for some time to come."

Larry Trojak is a communications writer for his own firm, Trojak Communications, in the town of Ham Lake Minnesota. He is a frequent contributor to construction and survey magazines.

A 1.519Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

 
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