Horizontal movements may affect angle estimation

[simenms]

Angles are updated using gyroscope data, and every N data rows triggering a Kalman filter that fuses accelerometer data to avoid integration drift.
However, when one exerts more horizontal than vertical movement on a sensor, this increase in acceleration in x- and y-direction is interpreted as a change in the attitude of the sensor. This has been somewhat counteracted by decreasing the frequency of Kalman filter activation, but the solution probably lies in improving the formulas for deriving angles from accelerometer input.