Mapping the Meridian

The Prime Meridian is one of Britain‘s most unique geographical features. As zero degrees longitude, mapping around the world is based on this line.

Survey car used to map the Meridian
Survey car used to map the Meridian

Running from the River Humber, just north of Hull, down to the south coast near Brighton, it cuts a 320km (200-mile) line through East England, passing through London in Greenwich. (Interestingly, the actual line is 200m - 656 ft - away from where it's marked.)

So, when the London Mapping Festival asked Topcon for ways to show how modern mapping could show the true Prime Meridian, Topcon's mobile mapping IP-S2 solution seemed like the obvious choice. Project Manager Mat Kellet said: "It's such an important feature for mapping, and now, using our IP-S2 system, we felt we could cover it in a way that hasn't been possible before. With a single operator we could record and process the data for the whole line in just two days."

Mounting the IP-S2 system on a Ford Mondeo, Kellet set off from Tunstall, Staffordshire on his journey south. It wasn't quite as simple as taking a single road, but with a combination of B-roads and A-roads he tried to keep as close to the line as possible.

"Much of the time this meant moving at slow speeds because of the road conditions, but when they opened out, I managed to travel at 65 km/h (40 mph)," he said. "Although the system works at up to 100km/h (62mph), for the amount of detail I wanted in the data, the slow speed made more sense."

In all, it only took him seven hours driving to complete the journey.

Number crunching

Back at base, once the data had been downloaded and the system prepared, he left it to run - seven hours on the road needed seven hours to process. The scale of the mapping was huge. Over those 320 km (200 miles), he recorded nearly a trillion separate points through the LiDAR point-cloud system, and the 12-megapixel camera took 80,000 individual photos. Yet the vast amounts of data were very manageable.

"To process the data we used a standard computer. You don't need special equipment to do it, just some time," Kellet said. "It produced 600GB of information - of that, 240GB was photos, 30GB GNSS information and those trillion points were just 120GB.

"That's one of the things we're very proud of with the IP-S2 system", he said. "With only one man, one car and one computer, we can easily map a huge area in such detail. This just wouldn't have been possible in the past."

Mapping the Meridian website

You can see all the data on the Mapping the Meridian website. It was also sent out to 85 schools along the Meridian as part of the festival. They were set challenges based around the information collected, and had to re-create the height of objects along the way in their playgrounds.

Representatives of local surveying companies verified the results, and the schools whose students got closest to the correct heights were entered into a competition to win Topcon surveying equipment.

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