We recently held a one day conference here at CASA called Smart Cities. For the conference we built various exhibition pieces and my contribution to the conference was the London Data Table, a projection table the shape of Greater London. The table had various visualisation projected onto the surface; from live aircraft positions, live traffic and bike hire usage to movies of public transport over 24 hours. We got some great feedback from the attendees and I thought I would share my documentation of the whole process of build the table, from start to finish.
Step 1: The Planning
The biggest issue in this project was size. How big do we make the table? Can we find a projector with a short enough throw to project to the table? How were we going to mount the projector. I downloaded the outline of London from OS OpenData (http://os.openstreetmap.org/data/) and created a pdf of the London outline, this would serve as our master vector throughout the process. I’d be lying if I said we knew all the answers the questions at the start of the project but with a few calculations and a lot of paper we mocked up the outline on paper (to scale) and stuck it to the wall of the office.
Planning the project this way allowed us to see that a normal projector would be impractical (due to the distance required to project an image of that size) and that we would have to buy a short throw projector, not ideal. Time was against us so we ordered the projector, took the leap and started to build the table.
Step 2: Building the Table
I wanted this table to become a piece of furniture! There was no point putting in all this effort to build a table which would only last the length of the conference and then started to sag, as MDF eventually does. So after some advice from the staff in the Bartlett workshop I decided to order a 10ft x 5ft (3m x 1.5m) piece of birch plywood. Birch plywood has excellent strength with a beautiful finish but is some what more expensive that MDF.
Here at the Bartlett @ UCL we have an excellent workshop that has a wealth of tools including laser cutters, a full wood and metal workshop, 3D prototyping and a CNC milling machine. This would cut the outline from our sheet. Armed with an Adobe Illustrator file of Greater London, I exported to DXF (a CAD standard file format) and loaded it into the milling machine. Watch the video to see what happened next.
Within 10 minutes we had the outline of London cut out. A quick chisel to remove the frame and we were ready to go into the preparation stage.
Step 3: Preparation
Out of the whole project this was the most boring part. Sanding the table down for preparation then painting a layer, then sanding again. Repeat this 4 times until I got an even finish over the whole surface and the table top was complete. I used a standard white emulation, the same paint you would use for walls with 10% water added to ease application. After a whole day of painting and drying and this was what the table looked like from above.
Step 4: Table Legs and Projector
I had the idea straight from the start that I was going to use a set of legs from Ikea to quickly make a table. A trip to Ikea later we had a set of T-Legs from a Galant desk. Screwed them on and we have an instant table.
Step 5: Align the projector
This was the most time consuming part of the project, aligning the projected image to the table. We mounted the projector on a basketball stand, which was a great idea from George MacKerron, which was custom mount screwed into the projector mounts made of the same birch as the table top and filled the base with water for stability. We created another vector to align the river Thames to the table and adjusted the height of the stand to fit. The results were fantastic!
So there you go, that’s how you build a table the shape of London and create an exciting new exhibit to show off the vast number of open data visualisations we create at CASA. In the next few posts, I’ll go into the in’s and out of the software and how I created the base software and the Aircraft Visualisation that we displayed on the table.