I am trying to integrate GPS and IMU but as a first step I am trying to use just 1d gyro and 2d accelerometer to work. Below is my model -
So, my question is .. after implementing this EKF, if I sigma_u for accelerometer is reduced to like 0.1 or less or in fact any lesser value, the error in comparison to GPS solution grows. It becomes around 50 m!! If I put in a higher value the error decreases. What am I missing in the model? Can anyone help me, please?