Hi Eduardo, I will take a look when I have some time.
In the meantime:
1. You are correct, there is a typo in equation 20.
2. In my paper, I used a west-north-down coordinate system, I did not know at the time that the conventional usage for aviation is north-east-down (NED). This often leads to confusion. Also, there is often confusion about the polarity of the accelerometer signals. For more information on coordinates that I use, see: https://github.com/MatrixPilot/MatrixPilot/wiki/UDBCoordinateSystems