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Some day laser scans on memory sticks may be all we have

  • 22 Jul 2021 02:31
  • 38

His Glasgow imaging team has seized the global lead in an esoteric craft – using laser beams to scan built objects into three-dimensional models. Now, in an international collaboration, Pritchard's team at the Glasgow School of Art will soon be creating perfect records of such structures as the Taj Mahal, Machu Picchu and the Great Wall of China.

A native of Winnipeg, Pritchard graduated from the University of Manitoba in 1990 and wound up in Toronto as a watershed moment occurred in the technology that enables architects to display their thinking.

"Architects are trained to think spatially," he said. "We think in 3 dimensions. We envision a structure in three dimensions and build it in three dimensions. But we represent it in two dimensions. So the client, who is not trained to think spatially, has to interpret it.

"In Toronto in the late 1990s, that started to change. There was a buzz in the air about representing things in three dimensions. Toronto architect Jack Diamond used a system called Lightscape. He would generate a computer model of a building, and then go through it adding lights ... You could tell the computer, `Put a 60-watt bulb here; put a fluorescent light there.'"

Pritchard immersed himself in new software like Discreet Logic  (now part of Kontron), from Montreal, and Toronto-designed Alias Wavefront (acquired by Autodesk ) that launched draftsmen into the third dimension. What emerged were building models that anyone with a computer could understand. In Pritchard's phrase, the viewer could "fly through" a building, gaining a crucial understanding – how it fit with its environment.

"In the midst of boom and change," he said, "there's a real danger of losing a city. People can't easily visualise the impact of developers' proposals. In two-dimensional drawings, things can look less imposing, less destructive of the old environment. With three dimensions, you see it as it is."

Pritchard moved to Glasgow in 2002 when the city came looking for someone to make an interactive, accessible, easy-to-use model of a four-square-kilometre swath of land called the River Clyde corridor, where development interest was intense.

In the world of contemporary animation, where online gamers zip among solar systems at the twitch of a mouse, a 3-D model of some streets may not sound impressive. But  Pritchard's models are faithful recreations. They are accurate to a degree never before achieved. If you took one of Pritchard's building scans and used it to calculate the area that was glass, your cleaner could order the right amount of product down to the last thimbleful.

When he started on the Glasgow project, Pritchard was using a technology called photogrammetry, where masses of photographs were assembled into a 3-D image by modellers. Cumbersome and slow, it demanded too much human decision for Pritchard who wanted a system that could capture data quickly and "indifferently" – recording everything without subjective influence. He chose the laser scanner.

The scanner did not originate as a tool for conservation. Ben Kacyra, (left) the inventor, was a California engineer who measured industrial plants. Refineries and power stations often need upgrading and as structures alter with time and use, they must be remeasured.
"In the 1980s we were doing nuclear power plants," Kacyra said. "We worked in `hot' conditions, where there's radioactivity. Equipment was very basic – measuring tapes, pencils and paper, slow and painstaking and also fraught, and I thought, there's got to be a better way."

In 1989 he started Cyra Technologies  to develop an instrument that could measure distance using a laser beam. Kacyra's first prototype required a Volkswagen bus for transport, but the next was small enough to hand-carry on to a ship that the U.S. navy wanted to measure.

The USS Tarawa was a 39,000-tonne assault ship stuffed with landing craft and jump jets. It was 250 metres, 10 storeys high and had been tinkered with so many times that no one could define with any certainty the maze of dimensions that made it up. Kacyra's portable scanner was able to assess this complex infrastructure and became an industry phenomenon. In 2000, he sold the company to Leica Geosystems

Two events brought Kacyra out of retirement. The first in 2001, when the Taliban in Afghanistan dynamited a pair of colossal statues of the Buddha (left) that had stood on a mountain side for 1,500 years. In 2003, an Iranian quake collapsed the city of Bam, (above) killing 26,000, erasing their ancient city.

Kacyra grew up in northern Iraq, and spent happy boyhood hours clambering through the ruins of ancient Nineveh. The obliteration of the two sites struck him with a sense of loss. Realising that thousands of locations lay at risk from war and natural disaster, and that blueprints of them did not exist, he set up (below)  CyArk , a foundation charged with digitally scanning and archiving 500 of the world's most important sites. Looking for partners, he found the Scots.

With a $160,000 Leica scanner – Kacyra's invention – Pritchard's Glasgow digital team successfully scanned four square kilometres along the River Clyde.

Nothing like it existed anywhere. The model comprised 1,200 buildings, rendered with breathtaking accuracy. In 2006, Pritchard's work caught the attention of Historic Scotland, who assigned him to scan an iron bridge in Dundee. When he got there, Pritchard found a dilapidated parade of metal loops and curves choked with weeds.

"To measure something like that with traditional methods – it's unthinkable," said Pritchard, recalling a past Toronto project involving a heritage site on Wellesley St. that had been broken into tiny flats. "In one whole day, two of us managed only 200 measurements, and that's just a bunch of rectangular shapes. In the same time scanning at the bridge, we collected 64m points."

Cyark (right) Spruce tree house

The ability to capture fine data in large amounts and perfect accuracy is crucial to Historic Scotland's conservation efforts.

The digital model of the royal palace at Stirling Castle is so exquisitely detailed that it looks like a photograph. But a photograph does not let you zoom inside, or generate a cross-section that is true to within a millimetre.

This year Historic Scotland announced a five-year, $2.5m scheme (left Edinburgh Old and New Towns for scanning) called the Scottish 10.

Pritchard will scan and model all five world heritage sites in Scotland, and five beyond its borders. Of the latter, only one has been decided – Mount Rushmore.

The imposing sculptures of  US presidents on a South Dakota mountainside are at risk of weather damage. Water can penetrate into cracks, freeze and expand, breaking off chunks of rock. That a team of non-Americans has been selected to scan the iconic site shows how far Pritchard has pushed the technique.

Recently, Pritchard and a team of Historic Scotland scientists clustered on a scaffold and peered at the stone roof of one of the country's most popular tourist destinations. The  Rosslyn Chapel, after the earls of Rosslyn, the 15th-century church is a dreamy Gothic fancy on the edge of a steep glen. Drawn by the pretty site and by speculative tales about the Rosslyns, some 40,000 people a year came to visit.

"Our plan was to slowly grow the number to 80,000," said Colin Glynne-Percy (right) of the chapel trust. "But in 2003 The Da Vinci Code came out. We went to 80,000 in a single year. The next year it was 120,000 and then 175,000."

The pilgrims attracted by the chapel's role in Dan Brown's book tramp the little space, setting up vibrations and adding their breath to the atmosphere, imperilling a site already weakened by the damp. Now the entire chapel has been scanned, inside and out. You could carry it around on a memory stick.


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