There is no reason to keep an uncertainty on the origin as it is then
already contained in the local position estimate when GNSS data is fused
in the filter.
- refactor all EKF backend output predictor pieces into new OutputPredictor class
- output states are now calculated immediately with new high rate IMU rather than after EKF update
- IMU delayed sample is passed as around as control data to avoid storing an extra copy and make the requirement clear
- don't store unnecessary IMU copy in class, pass it through where required
- remove custom pi constants
- remove unused fields from ahrs_ekf_gsf (vel_NE, fuse_gps, accel_dt)
- explicitly initialize everything in header
- apply PX4 code style
- set GPS velocity before yaw estimator update, not after
- working towards keeping all height source (baro/ev/gnss/rng) handling as consistent as possible, possibly refactoring these out into separate classes later
- a growing number of samples come into the backend with the time
already delayed (sensor's interrupt setting timestamp sample)
- if the incoming timestamp is already delayed then the new data checks
(relative to latest IMU) can be slightly wrong
- handle almost all timestamps and checks on delayed time horizon,
except for explicit checks of new samples
- isRecent() and isTimedOut() helpers use delayed time
- add new isNewestSampleRecent() used for checking the incoming
timestamp of the incoming (adjusted) data
bresch