More4 Lake District Rescue

Viewers who have been following the fortunes of Mountain Rescue crews in More4’s new documentary 'Lake District Rescue' will have seen the scale of the challenges rescuers face with the terrain.

The peaks and troughs that characterise the Lake District National Park landscape are illustrated by dramatic Ordnance Survey 3D imagery to demonstrate the rescue routes taken to reach each casualty.

During the series, Mountain Rescue crews reinforced the importance of navigating with OS mapping to keep safe. And subscribers to OS Maps can access 3D flythroughs to preview routes they plan online.

Senior Research & Innovation Scientist at OS, Jon Horgan, worked behind the scenes on the show, and he explained the craftsmanship behind turning basic 2D images into sweeping 3D graphics suitable for the big screen.

Where did the data come from?

“It was based on completely standard aerial imagery that was never captured with generating a 3D model in mind.

“But it is perfect for mountainous locations because there's not that much feature data there.

“We used a 3D mesh based on five blocks of imagery captured by our flying unit over a period of three years, all at different times of year. The trick is to stitch all the individual blocks together and process them as one to generate a mesh model. The tool I used for generating 3D mesh models was Skyline Photo Mesh.”

What challenges had to be overcome?

“I had to take as much care and attention to ensure the colour matching wasn't compromised because otherwise it can look a bit like a patchwork quilt.

“You've got shadows going in all different directions and you're trying to basically resolve the temporal nature of the data.

“One of the main issues was where there are overlapping image blocks, particularly over water bodies because the nature of water means heights are different in images. This affects the mesh due to specular reflectance.

“You must be very, very careful in basically flattening out the lumps and bumps and floaters over water bodies. That was something that required the addition of heighted water body polygons – handcrafted after the event – to make sure it didn't look spikey. Otherwise you would have had tsunamis in the lake or you'd have big floating clouds above the water, which is not going to look great in a 3D model.”

What have you learned from the process?

“I think what we've learned as a wider group is that imagery is good for generating very large area meshes in the mountains and of moorland areas, or more broadly rural areas. I don't know how much of the country is mountain or moorland but it's significant.”

What insight can be gained from this kind of 3D mapping?

“There was some initial feedback from the Mountain Rescue teams. They said 'hey, can we have this, this is really good stuff. Potentially this would make this would help us to plan things.' That's the takeaway we got from the emergency services.

“It backs the hypothesis that OS should be creating some 3D data that's based on standard imagery. We are effectively turbo-charging the value of the imagery and in effect processing it like a catalytic converter to generate the good 3D stuff that comes at the end.”

What were you thinking when the show aired?

“I'm sure it will have surprised some people because they don't think of OS producing that level of information. I think it could be a bit of an eye-opener.”

Lake District Rescue airs every Sunday at 9pm on More4 (repeated Saturdays at 8.55pm). The final episode is scheduled for 28 April. The series will then be available on the Channel 4 On Demand platform.