EKF2 and uBlox M8P RTK

2

Hi,

Trying to answer your questions in order:

  1. Checkout the in src/lib/ecl/matlab/scripts/IntertialNavEkf/GenerateNavFilterEquations.m for the derivation of the extended kalman filter (EKF). The EKF is actually running on a delayed time horizon in order to enable fusing measurements at their matching time. Therefore, there is a complementary filter which produces the inertial solution at the non-delayed time horizon and using the EKF output
    for correcting it’s state.

  2. You would need to have a look at your log and evaluate if the complementary filter is tracking the ekf output to your satisfaction. That would depend on your system. I think we log the innovations of the complementary filter, I think EST4.e1 to e3.

  3. You are right about the gps noise parameters for RTK. However, you should still have a look at your position and velocity innovations and innovation variances in the log and tune them according to your needs. In general I would recommend you to use the replay tool documented here
    http://dev.px4.io/ekf2_log_replay.html
    One you have captured a single replay log on your physical system you can use the replay tool
    to tune the ekf parameters. You will see the effect o parameter changes on the filter outputs.