It doesn’t often happen that you are sitting in your office on a dull, wet London morning and your boss walks in and asks whether you'd like an all expenses paid trip to Australia. 'Oh by the way, because we want you to arrive refreshed and ready to work, we'll send you business class!' One week later I checked in at Heathrow Airport and was on my way.
The job was ‘imaging Jim, but not as we know it’: A 3D laser scan survey of Sydney Harbour Bridge (so not just a peach of a trip but a peach of a job too!). A laser scanner is somewhat like a laser rangefinder but it measures X,Y,Z co-ordinates at the rate of six thousand a second. A full 360-degree scan takes about four and a half minutes and produces a ‘point cloud’ of about six million points. These can be used to produce a CAD plan or a full 3D model. Surprisingly, there is a lack of detailed information about Sydney Harbour Bridge and this technology offers a good way to provide it.
|Image courtesy of Mike Annear |
The team on the upper cord of Sydney Harbour Bridge with the laser scanner
A laser scanner, while portable in name, is quite heavy and valuable so I had been provided with an advance to pay for the excess baggage and a temporary export license. Arriving at Heathrow towing something that looked like a small thermo-nuclear device, I walked up to the vacant First Class desk to ask for advice. Next thing I knew I was checked in, with a porter escorting me to the customs desk, all with no excess baggage fees. I sent a text to my boss asking if I could keep the money and she replied: 'No, just drink the Champagne!' I then settled into a nice comfortable seat for the long haul to Australia.
The team for the survey consisted of myself, Nigel McDonald and Mike Annear who has enjoyed a colorful career. Once a professional diver, Mike had also worked as a photographer before getting interested in 3D modeling and paragliding. I don’t think he dives any more but he still does the rest and you should have a look at his website. He is not the tallest person in the world but immensely strong and a delightful bloke to work with. In addition to setting up the laser scanner, we had to pick up a few bits and pieces that I had not brought with me; steel toe-cap boots, head torches for working hands-free at night, and of course a big floppy hat!
The first day, we worked our way round the South shore. Individual laser scans can be linked together or ‘registered’ to create a large scene. On that first day, we recorded about twenty scans. The finished model was over two hundred. The second day we did the same on the North shore. The following day was a Sunday and we spent that working our way northwards along the railway (there was no train service that day) and then back along the pedestrian walkway on the seaward side. This left the main arch for the final day of the survey.
We didn’t start too early on the final day: It was going to be a long session and in any event, we were not going to be allowed full access to the bridge until after the final ‘bridge climb’ tourists had gone. The bridge's main steel arch is comprised of both upper (on which tourists are allowed to climb) and lower chords connected by girders.
We started on the lower chord and worked our way from the south east pier over the arch until the scanner was in range of the north east pier then crossed over a narrow companion way and worked our way back on the other side. Nigel and I looked after the laptop, batteries and tripod whilst Mike took charge of the scanner. Despite its weight, he never seemed tired.
We could not ascend the upper chord until the last bridge climbers had finished so we grabbed a bite to eat and watched the sun go down. By eleven o’clock it was time to go and we made our way back up onto the bridge. We followed the same pattern as with the lower chord and the view was stunning. The lights of Sydney were ablaze together with the car headlights streaming across the bridge.
If you do the bridge climb as a tourist, you are not allowed to carry anything that can be dropped. Since we were working on the bridge we had the luxury of carrying cameras. Unfortunately, we were only able to carry a single tripod, which of course had the scanner on it. Nevertheless, there was plenty of nice rigid steelwork on which to rest a camera. One of my pictures won the Institute of Highways and Transportation photographic competition the following year but my personal favorite is the one you see below. It was shot with a D100 (quite modern at the time) and an 18-70mm Nikkor lens. For some reason, the Exif data didn’t record the shutter speed but it was probably half a second or so. It was shot as a JPEG because, although a D100 could shoot RAW, the length of time it took to write to the card was a real nuisance.
Did I take lots of pictures? No, not really. I could have happily spent all night up there shooting away but I still had a job to do. Yet I will remember that night for the rest of my life and how the picture that graces the home page of my website came to be created.
Geoff Helliwell spent over thirty years working as an industrial photographer for the Transport Research Laboratory (TRL) in the United Kingdom. He now works freelance and his website can be found at www.oaktreeimaging.com
Jul 14, 2014
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