Shoe-Mounted Inclinometer

Creator rabbitcreek has been doing walks up a mountain trail, and wondered what the actual incline was, and how it could be m. A smartphone can, of course, measure the incline as you tilt it on its side. However, that doesn’t solve the issue of actually measuring the angle you’re walking on as you tend to keep your body mostly upright. Rabbitcreek’s novel solution was to create a sensor package that straps onto your shoelaces, then sends data back to a smartphone via Bluetooth.

As described in the project write-up, the inclinometer uses a 9DOF BNO055 IMU sensor fusion breakout from Adafruit to track one’s foot position. A Seeed Studio XIAO ESP32C3 board provides processing for the unit, along with Bluetooth connection capabilities and LiPo battery charging. A 3D-printed housing keeps things together and protected on long walks.

While the electronics configuration is fairly simple, the real magic is in the processing. Upon bootup, one must set the shoe on a level position to sense its orientation. When walking, the inclinometer constantly checks to see when acceleration in the Z-direction is less than a set value and waits to see if it stays at rest for 100ms. When this happens, the pitch is measured, filtered, and averaged until acceleration starts again. Results are sent to the BLExAR app on an iPhone which adds location and timing data.

The device is impressively precise, showing a ±1 degree of variation walking down rabbitcreek’s driveway during testing. Collected angle info could be used to improve trails, or simply to track the progress on what kind of slopes you’re able to traverse. It can also be integrated with Strava if you like, using a bit of spoofing described here.