Creating a virtual tour of WWI tunnels
Important World War I tunnels dug by Kiwis under France have been surveyed with exacting detail and will be converted into a 3D virtual reality tour. Paul Gorman reports.
Historic chalk tunnels hewn by New Zealand soldiers in France during World War I are being protected with surveying science.
More than a century ago, they resorted to picks and shovels to carve out the military tunnels, which riddle parts of northern France. Now the University of Otago’s School of Surveying has used the latest technology to record every detail of large sections of the labyrinth that lies below Arras, 100km north of Paris.
The billions of survey points collected with a terrestrial laser scanner will eventually be subsumed into a ‘‘virtual visit’’, now under development. Using three-dimensional gaming technology, anyone will be able to ‘‘walk’’ around much of the maze, which is about 15 metres underground. Access to the actual tunnels is restricted.
The surveying of the World War I tunnels has been a huge project. Earlier this month, senior surveying lecturer Dr Pascal Sirguey handed over to the city of Arras 3 terabytes (3000 gigabytes) of surveying data, along with accompanying animations of the tunnels.
Included in the collection was New Zealand names, sketches and graffiti etched into the rock in the lead-up to the May 1917 Battle of Arras.
The Ronville network of tunnels link with historic chalk quarries and form part of an underground military complex more than 2km long, built from Arras under no-man’s land and across to the German trenches. British troops used the tunnels for a surprise attack on the German frontline.
They were secretly dug by members of the New Zealand Engineers Tunnelling Company in 1916-17. Seven of the diggers were graduates or staff from the university’s then Otago School of Mines.
At one stage the tunnels were home to nearly 10,000 troops, with electric lights, water, kitchens, toilets and a light rail network.
As technically challenging as the survey of the tunnels has been, the next step – to make them accessible in the virtual sense to many thousands of people – is even more ambitious.
Final-year surveying student Damien Houvet from the Ecole Superieure des Geometres et Topographes (ESGT) in Le Mans is now at the University in Dunedin until the end of June, working out how to turn the data into the virtual tour.
‘‘It will be like a video game. You will be able to navigate easily in all directions in the tunnels.
‘‘It would be difficult to create the whole virtual visit in the time I have here. But it is most important to be involved in the research and development of it, and find the best way to create virtual visits with such huge data,’’ Houvet says.
Sirguey says it is important to put such a vast amount of information to good use.
‘‘Otherwise we can keep on creating massive data that never sees the light of day.
‘‘Capturing the data is not that difficult anymore. There is a challenge to survey it correctly, to make the data worthwhile and that is why surveyors still exist – we are not just here for pressing the buttons.
‘‘The big question for surveyors now is: ‘How do you start making this massive data reality capture relevant?’.’’
The answer is interactivity, he says.
The main survey of the tunnels was carried out in July last year using the most sophisticated equipment available to the team.
Surfaces were created from the surveyed points – millions of them. Raw survey data was cleaned up to remove duplicate points, double reflections and anachronisms such as the legs of a survey tripod.
Once the surfaces were created, textures were added and photographed images projected back on to the surfaces, Sirguey says.
‘‘Then you need to create a topology, which means you cannot walk through a wall, for example, and then you need to enable all that into a game engine, just like 3D games, where people can move in, turn, and you get that interactivity element through the sensors.
‘‘Our colleagues and collaborators on the project from the French national school of surveying at Le Mans have quite a bit more experience than us on this next level of surveying, this reality capture.’’
The tunnels have changed during the past century and the surveying, and virtual tour, will help with their preservation. In World War II they were used as air-raid shelters by locals and were thought of as possible nuclear fallout shelters during the Cold War.
Erosion is also an issue, with occasional falls of chalk from the roof and tunnel walls.
School of Surveying academic Richard Hemi says the need for preservation is paramount.
‘‘The tunnels are a real physical New Zealand monument, with the graffiti and the names. It has a real New Zealand signature to it that, to a large extent, had been forgotten and not really welldocumented.
‘‘This spatial documentation is a fantastic opportunity not only to preserve it, but to then lead on to that further interpretation of that story and history, in a very modern way.
‘‘One of the things you can do with the virtual environment is to add tags or keypoints, where you might be ‘walking’ along a hallway or a tunnel and there’ll be a numbered tag or box, and if you click on the box, like gaming for kids, information or a photo will come up.
‘‘So if you walk along a tunnel and see an image or a signature, and you click on it, a really good photo of that signature might come up or a photo of the soldier and where he was from,’’ Hemi says.
The technology is being used on heritage sites and projects closerto-home.
Senior students have been surveying historic buildings around Dunedin and features such as the lime kilns on Otago Peninsula, tunnels at Taiaroa Head, the old battery at Macraes Flat and railway tunnels around the region.
Paul Gorman is a senior communications adviser at the University of Otago.