Jun 23, 2016 | By Alec

There’s a lot more free 3D data available than most people are aware of, even of some of the world’s largest cities. Among them is the city of London, of which the British government has been releasing extensive LIDAR surveying data online. Fortunately, map-crazed San Francisco-based programmer Andrew Godwin caught wind of that initiative, and used the newly released data for his “London Rising” project: a gorgeous 3D printed scale model of central London packed with 3D relief and details.

Key in this cool project is the Open Data initiative, through which the British Environment Agency has been releasing LIDAR (Light Detection and Ranging) data to the public. LIDAR technology is frequently used by surveyors to accurately capture geographical details (for map making purposes), and has been around for decades. Over that time, the Environment Agency has collected a huge amount of geographical data, which is a treasure trove for map enthusiasts like Godwin.

As the San Francisco-based Brit revealed, he has been crazy about maps for years and has been playing 3D map data for a long time. “Thus, when I finally gave in and bought a 3D printer at the start of this year, I'd had a rough project in mind for a while - to 3D print maps with actual vertical relief,” he recalls. When learning about the UK's ongoing Open Data initiative, a fantastic idea rose in his mind. While the data for a large part of the country hasn’t been released yet, excellent models for central London (where Godwin grew up) were already available. “London Rising” was born.

LIDAR data in QGIS

Unfortunately, the LIDAR data proved to be more cumbersome than initially anticipated. “The data is collected from a low-flying aircraft that samples point heights in a cone below it with a laser ranging system; this means the data you get back is essentially a grid of point heights every meter,” Godwin explained. “They jump around a bit as the natural error of laser ranging creeps in, so even a perfectly flat roof will come back as a bumpy mess of heights. That means you have two problems - turning the point cloud into something you can actually feed to a 3D printer, and refining the resulting model so it's not a jagged mess.”

Turning the point cloud into a 3D model was easy, but making it 3D printable and watertight was far more difficult. Each detail (or in this case, each rooftop and wall) needed to be filled with polygons to form smooth models. Time-consuming and very difficult to do, Godwin simply did not possess the necessary skills to realize this. Instead, he went for a more sensible solution. “I just took all the data, averaged out points to make a lower-detail height map, snapped the heights to 3m intervals and applied neighbor-based smoothing to the whole thing,” Godwin recalls. This also solved another problem, as the original file was over 200 MB in size, took extremely long to open in regular viewers, and was impossible to slice.

The resultant file wasn’t perfect, but very complete and packed with London’s railway viaducts, bridges, parks and even the Crossrail boreholes. What’s more, the STL file was ‘only’ 20MB in size and can be found on GitHub here.

But 3D printing wasn’t without its challenges either, especially as Godwin doesn’t have a lot of experience with the technology. Using his Rostock MAX v2 3D printer, he spent days experimenting with the different settings, temperatures and ABS and PLA materials. Eventually settling on PLA, it took some time before he could 3D print problem-free. “The first 20 tiles came out with various defects or often the buildings would be blobby or strings of plastic would be left on the model,” Godwin says, but saw enough evidence of progress to keep him going.

Finally, he settled on 3D printing 48 different tiles, which together form central London from Hyde Park in the west to Godwin’s own old flat near the Thames. “I chose to print them at a size of 7.5cm on each side, for a final size of 90cm long by 30cm high,” he says. “To 3D print a 7.5cm tile took between 1 and 4 hours, depending on the level of detail. To print a 15cm tile took between 3 and 12, which is bad for two reasons - it limits the times you can print things, as the printer should really have someone around while it's printing, and it means any print failure undoes a lot more work.”

While in hindsight Godwin preferred larger tiles, he was nonetheless faced with an ambitious 3D printing project that took several weeks – with 3D printing mostly taking place in the evenings and weekends. These tiles were subsequently glued to a foam board, with wooden spars across the back of the frame for extra rigidity. “The main problem I encountered when prepping all the tiles for mounting was getting them all aligned; this is where I realized I should have gone for the larger tiles, as it would have meant four times less complexity, and less gaps,” he recalls. Some tiles had a very slight rhomboid shape, making a few gaps impossible to avoid.

But the final result is still absolutely stunning and exhibits a remarkable level of detail. Who wouldn’t want this mounted on his wall? What’s more, it only took around $200 to make, complete with running costs and filament. A fantastic example of what can be achieved with something as basic as old LIDAR data. The London map has already inspired Godwin to apply the same principles to another city, perhaps even to San Francisco and Oxford to complete the trio of the cities he has ever lived in.



Posted in 3D Printing Application



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Jasper wrote at 7/18/2017 7:42:38 PM:

Great inspiration, how did you make a 3D model out of a LiDAR file (.las/.laz)?

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