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Post date: Dec 16, 2016 10:50:57 PM
Intro: I wanted to see how I could measure and display the forces of waves on bodies of water that I walk past everyday in Providence, Rhode Island. I walk and bike alongside the Providence River on paved roads and bike paths that line the eastern bank. At speed and at a glance, much of the river seems flat, with barely a wave or even an interruption save for a few birds and the occasional tourist gondola. I set out to see if an arduino could measure forces from waves and then generate data similar to the way a harmonograph artistically reveals forces of gravity.
Construction: I made a buoy out of blue foam, a ziplock bag, and duct tape. I put and Arduino Uno and an IMU 6 degree of freedom motion sensor in the bag. A USB cable acted as a tether. For a first run, I sent data via USB straight to my computer. I tested in my bathtub before throwing the device in the river. It worked perfectly. Total cost was ~$3 in supplies.
Sites and Data Collection: I chose three sites to measure wave activity. The sites were selected for convenience, accessibility, proximity to the path I usually walk along, and variety of wave conditions ue to exposure and wind. Two sites were in India Point Park beyond the Providence storm barrier, and the third was in the Providence River near RISD campus. I gathered roughly 2000 data points per location.
Process: Gently lower Arduino into water, check for data connection, record, retrieve. Try not to drop phone or laptop into water in the process. Save data to Excel and repeat. I measures both acceleration (as a proxy for force) in 3 axes (X, Y, Z) and gyroscopic data in 3 axes (Roll, Pitch, Yaw.)
Insights
Using digital tools to measure analog forces in nature changed my perception of the forces, and the spaces I was walking past, even before I could visualize the data. I reached a number of conclusions just moving from site to site.
You have to be really close the water to perceive small differences in wave patterns. Ideally at the water line, but…
It’s really difficult to get access to the water line in urban areas,
Because there are a lot of obstacles that are built, and natural.
The built obstacles include fences, walls, roads, and ironically, even a dock that I didn’t have access to for liability reasons. So I was stuck taking on the natural forces,
Which included slippery rocks, gravity (a threat to my safety and my laptop), dead fish, bird shit, and a a very large swan.
Initial graphs This is data that has been slightly cleaned to remove outliers and smoothed in Excel. Nothing else. I’m considering keeping XY graphs, moving to conventional wave graphs, or something else entirely…
Going Forward I don’t think a data viz is the best way to showcase this data. I spent some time experimenting with waves and lights and shadows and film and think i’ll likely push the data back into arduino to manipulate servos to replicate the wave actions in a tub of water with a light underneath.
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