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Research Log – 09/12/2013


Written by Jimmy Lee on September 17, 2013 in General

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ae1b83ecbee137927d2079336d5dbde9_largeLike a scene from Pixar’s UP, Plant With Purpose’s staff watched in anticipation as fifty multi-colored helium balloons slowly lifted from our office lawn carrying with them a camera. This camera was modified to record both near-infrared and visible light. Healthy plant leaves absorb visible light and strongly reflect near-infrared light, while unhealthy plants and its surrounding landscape reflect visible light. By comparing the difference between the amount of reflected visible and near-infrared light, we’re able to perform NDVI (Normalized Difference Vegetation Index) analysis, a measurement of the health of plants and the amount of vegetation in a given area.

photo (4)The modification was deceivingly simple: open up the camera, remove the infrared filter, and tape a special blue filter to the front of the camera lens. The result was an inexpensive yet effective camera that could record both visible and near-infrared light.

So why all the balloons? The plan was to test how the camera would function at a relatively high altitude and whether the resolution of the resulting images would be suitable for NDVI analysis. The end goal of this experiment would be to attach the modified camera to a remote controlled quadcopter and snap photos of Plant With Purpose watersheds and reforestation projects around the world. Over time, this information would give us an idea of the status of our reforestation work and allow for better-informed decisions about future interventions. Unfortunately, quadcopters can cost hundreds of dollars.

After calling store after store for helium balloons (who knew there was a worldwide helium shortage), Ben, our new grant writing intern, saved the day by finding a store, which carried helium balloon kits including both the helium tank and balloons. Once the kits arrived, we began inflating the balloons and attached them to our makeshift zip-tie camera basket, which was then connected to a fishing pole (yes, we’re all about low tech solutions).

photo (5)After all the balloons were blown up, it was time for launch. We aimed past our office complex towards Rose Canyon Creek. The balloons floated over the row of cattails and toward a grove of trees. But, as if Murphy’s Law suddenly became fact and the balloons were about to clear the tops of the trees, the fishing line began to unfurl from the reel, tying itself into knots. The tension of the fishing line combined with strong winds began pushing the balloons lower and lower into the canopy of the trees.

In a moment of desperation, we cut the fishing line and tied it to a spare reel and the balloons cleared the tree canopy. We gave the balloons more line and the camera finally reached the proper altitude. But as soon as we stopped, the line snapped from the tension (most likely at the point where we tied the two lines together) and released the balloons to the wind. And all we could do was watch as the bouquet of balloons and the camera floated higher and higher towards north San Diego.

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The experiment was not a complete failure though. Here are some takeaways:

  • tumblr_m0eeo6eAWS1ql02ego1_500The modified infrared camera works. From photos taken prior to balloon experiment, enough visible and near-infrared light gets recorded to perform NDVI analysis.
  • Use a better fishing pole or a different reel for the line. A kite reel could be a good alternative.
  • About 50~60 helium balloons are required to launch a small camera. At about $50 for two balloon kits, investing in a remote controlled quadcopter might be cost effective in the long run.
  • Do not take any identifying photos of staff before launching 50 balloons.
  • Effect of Murphy’s Law is inversely proportional to the level of technology used.

If you find a camera attached to a number of deflated balloons, please return it to the address found on Plant With Purpose’s website.


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