Timo Denk's Blog

Parachuting Sensor Data

· Timo Denk

During my first tandem parachute jump in August 2022, I collected some sensor data with a smartphone (the app is called Sensor Logger) and a Garmin watch. Below is a little analysis of the recordings. The source code for data loading, denoising, and plotting can be found here.

The plot shows the altitude as measured by the phone barometer. Annotated are the different flight phases: waiting on the ground, flying up aboard the airplane, the short free fall, the gliding phase (with the parachute deployed), and lastly being back on the ground.
The plane which carried us up to around 3,500m.
Zooming in on the most interesting events: jumping from the plane (that’s when the altitude drops rapidly), parachute deployment, and touchdown. We spent about 34s in free fall and a little over three minutes gliding with the parachute deployed.
During the free fall we quickly (!) reached the terminal velocity of around 200km/h. The gliding phase came with a vertical descent of about 20 to 30km/h, interrupted by some maneuvers (curving left and right). The fast drop in velocity is particularly interesting: That’s the parachute deployment during which one experiences a strong deceleration.

Acceleration data can be derived from two different sources. The acceleration sensor itself and via the velocity computed from the barometer’s altitude data. I had to denoise the barometer data aggressively, hence it is not perfectly aligned. It seems like the maximum deceleration we experienced during the parachute deployment was slightly above 2g.
Lastly – and in my opinion the most hilarious – is the heart rate data. I got fairly nervous on the plane where my heart rate went up all the way to above 115bpm. During the free fall it dropped to 100bpm and only the event of the parachute deployment made it bounce back a litte. While gliding down gently, I remember looking at the watch and being surprised myself, to see the heart rate drop as low as 70bpm. The anticipating of the landing brought it up to 100 then.