No, I didn't fix position or velocity with a priori covariance. I did lower the a priori covariance to 10 m position and 1 m/s velocity. They still need to be adjusted, we are using the compensative accelerations instead of adjusting for drag and MU/J2. Did you try leaving the a priori covariance for MU, J2 and CD high?(posted 8833 days ago)As far as reasons your problems...my residual RMS drops significantly, to under 10 meters, but the RSS of my position error dropped as well. You are using xyzDMC right? Try lowering you tau and sigmas to small numbers (1e-10). The effect of this will be as if you aren't using any process noise. Use this to check to see if you have things coded ok. If that doesn't show you something, email me all of your code and I'll take a look.