Should we put "x_freerun", instead of "x_nature" in state vector?
Otherwise, the comparison is not meaningful at least for me, because in generate_analysis_3dDet.py, it reads the initial condition generated by analysis_init.py. In this situation, if you choose "skip", you get the same trajectory as nature run.
In addition, if we want to compare freerun and specific DA methods, they start from the different initial conditions.