CdA from a wind sensor
A standard field test for aerodynamic drag (CdA) assumes still air, which is rarely true on the road. The iBike Newton is usually treated as a rough power meter, but it carries the sensors needed to drop that assumption: a pitot tube for air speed, an inclinometer for road slope, and a barometer and thermometer for air density.
Approach
I use the Newton the other way round, as a wind and environment sensor, and take the power from a crank power meter. With the wind measured second by second, the power equation becomes a linear least-squares problem in two unknowns, CdA and rolling resistance.
The software pulls the rides straight from the device over USB, without the manufacturer’s program, and works from the raw sensor counts.
Status
The toolchain is built and tested on simulated rides, and the USB link works with the real device. The first real rides are still to be done, so there are no results to show yet.