How to get the bias estimates

[amberwood31]

Hi, dear author

Thanks for sharing your work.

May I know what's the correct way to extract the bias estimates after the preintegration?
My understanding was that since the bias was explicitly modelled in the state vector, it would also be updated after integrating the measurements. So I tried adding these lines to the test program.

  std::cout << "Preintegration bias:\n" << pim.b()[0] << ", " << pim.b()[1] << ", " << pim.b()[2] << "\n\n" << std::endl;

I expected to see some small values that would be the gyro bias estimates, but I'm getting all zeros.
Please kindly share some insights!