February 12, 2009

point cloud data with a superimposed traffic circle

101 Avenue East in Grande Prairie


The laser scanned image (above) shows the point cloud data with a superimposed traffic circle over the physical material. The data points along 101 Avenue East in Grande Prairie are visible.

Surveying Technology

Laser technology adds third dimension to land surveying

Motorists driving through Grande Prairie’s busy downtown core last fall could be forgiven for missing an extensive surveying project being conducted for the city.

No roads were closed and no detours were set up.

The only indication that something was happening was a small piece of electronic equipment mounted on a surveying tripod.

Stephen Vickers, project manager of Grand Prairie-based Focus Corporation, said his company used a terrestrial laser scanner last October to scan several blocks, as well as some public open spaces, to provide the city with data on their grid system.

“We were able to capture a huge amount of data – 81 million survey points – more accurately and quicker than using conventional techniques,” he said, adding that the emerging technology allowed his company to reduce project time by about 50 per cent over traditional surveying methods.

Vickers said that conducting the survey with the laser scanner also eliminated the manpower of setting up barricades and kept the one-man crew away from oncoming traffic.

“We can set the scanner back several metres and scan in safety,” he explained.

In addition to saving time and making the work safer, Vickers explained that the 3D imaging equipment, a Leica Scan Station 2, provided a much more detailed picture of what was being surveyed.

With a range of 300 metres and an accuracy to three millimeters, he said that his laser scanner, which looks like a conventional surveying set up, is capable of scanning 50,000 survey points per second.

With 3D laser scanning, the unit sends out a laser beam, which travels in an up and down chopping motion as the unit swivels around in a 360 degree rotation. As the beam hits the target, it sends back a return of data, which is recorded as a point.

The millions of individual points combine to create what is called a point cloud.

The project manager explained that the resulting point cloud looks much like a traditional photograph, until you zoom in and see the gaps between the individual points – each one carrying a measurable x, y and z coordinate.

Although the scanner works with custom software, Vickers said that the scanned data can be imported into programs such as CAD, which makes the reading of data more accessible.

Individual parts of the point cloud, including vehicles and pedestrians can then be removed to provide a more accurate picture of the terrain.

laser survey unit

The laser survey unit can be moved and operated by one person.

But as accurate as the laser scanning is, Vickers said he doesn’t see it replacing conventional surveying methods, at least not yet.

“It certainly isn’t a panacea tool,” he said, adding that he believed that there will always be a need to mix technologies.

“You are always going to get little data voids you’ll need to go back and fill,” he said.

Vickers is aware that the technology has come a long way since it first appeared at the turn of the century.

Back then, a unit with one tenth the functionality of his company’s current model cost $250,000 and fit in the back of a truck.

The unit he uses today costs about $120,000 and can be carried and operated by a single person.

However, he anticipates that the best is yet to come.

“I think it’s inevitable that in a couple of years you are going to see two or three technologies combined,” Vickers said.

He anticipates future models will include conventional surveying, laser scanning and GPS functionality.

As technology continues to evolve, so too do the applications for scanning technology.

Vickers said that scanners are becoming more commonplace in crime and accident scene forensics.

Because the technology has a photographic component, Vickers explained that the scanner can pick up differences in materials that may not be visible to the naked eye.

For example, a glass building will send back a blue return, while black rubber shows up as a red return.

“The change in surfaces and change in material is all becoming apparent with the scan data,” he said.

His company has used the technology primarily for Alberta’s oil and gas industry. This includes recently lowering the scanner into confined tank spaces at the Shell Scotford Plant in Fort Saskatchewan.

However, he said he sees the infrastructure market as being the next big growth area, particularly with roads and highways.

While the technology has been around for almost a decade, Vickers said there are only about a dozen units in operation in B.C. and Alberta, but he expects that number to increase as startup costs continue to decrease.

“Historically, everything is 3D,” Vickers said.

“We’re now in a situation where we don’t have to do that – we don’t have to dumb down the world we live in.”

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