Chasing rainbows – Physics triumphs at Twizel
that during that second, cars move 30m on the open road and the light is spread over three of the pixels of the satellite image, appearing as rainbows on the roads. We needed to be able to prove it, so we did a ground truth experiment on a day when we weren’t rowing.” Positioned in pairs at 800m intervals along the road between Twizel and the canal at Ruataniwha, the boys videoed the passing traffic. Later, Andrew looked at the videos and the recorded times, and using Year 10 Physics worked out the speed and whereabouts of the vehicles when the satellite took the image. “We then investigated. It was just like hunting asteroids, except that instead of looking up, we were looking down to find moving cars on the images.” All the boys thought the rainbows on the roads were cool and could understand why they were appearing, and were interested “If we can detect and count the traffic on country roads in satellite images, we can work out the traffic density on every country road in New Zealand, which has to be of use for those involved in the planning and maintenance of country roads.” Several of the boys have expressed genuine ongoing interest in the experiment, and Andrew now unashamedly calls it his “research hobby.” Using the available satellite data, applying it in a real world setting and presenting that the experiment was conducted to prove what was going on, says Andrew. And the wider ramifications?
They went to Twizel to row, but ended up chasing rainbows through the Mackenzie country. A group of 10 Year 10 boys learnt all about mental flexibility when their efforts on Lake Ruataniwha morphed into a science project using satellites to look at the earth. So began “Chasing Rainbows: Monitoring Road Traffic using Multispectral Satellite Imagery”, a paper presented at the New Zealand Institute of Physics conference in April by Physics teacher Dr Andrew Taylor, and then reworked as “Astronomy Looking Down” and presented at SuperVOSS 2019, the conference for Vatican Observatory Summer School alumni, at the Vatican Observatory, Castel Gandolfo, Italy, in September. “It’s a great example of how projects can develop from a question or an idea, and have interdisciplinary connections,” says Andrew. While studying some satellite images of the Mackenzie region, Andrew happened to see rainbows on the road, and together the group decided to try to explain exactly what they were. The European Space Agency’s Sentinel satellites carry a range of technologies, radar and multispectral imaging instruments for land, ocean and atmospheric monitoring. The data gathered as these satellites orbit the earth is freely available to anyone in the world. “We learnt that the satellite measures blue, green and red to get its colour pixels and each measurement is half a second apart. We know “It’s a great example of howprojects can develop froma question or an idea and have interdisciplinary
the research findings at conferences facilitates cross-pollination of ideas with people around the world. “These represent marvellous examples of countries collaborating on science matters. It’s a fascinating experience.”
connections.” Dr Andrew Taylor
College Issue 37 2019
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