Initialization and Practical Estimator Guidance

• Static start.
  • Every run opens with the vehicle on the ground: PX4 IMU sees ~9.8 m/s² with near-zero rotation.
  • Use the leading samples — gated by low |gyro| and |a|≈g, not a fixed count or an external takeoff flag — for gravity-vector attitude initialization and accel/gyro bias seeding.
  • On most runs the opening static rest is followed by a deliberate VIO-initialization excitation (a smooth impulse along the IMU z-axis then smooth 6-DoF excitation), after which the vehicle is set back down before the real trajectory begins (paper §6). So the leading segment is two static blocks bracketing an excitation burst, not one continuous rest — a signal-gated static detector picks both static blocks and skips the excitation on its own; a fixed-count leading window would swallow the excitation. outdoor_1 shows no such early excitation, so treat it as typical-not-universal.
  • The 4 h static set gives Allan-variance noise parameters and per-IMU residual scale.
• Choose the IMU deliberately. PX4 (ICM20689, damped, near vehicle centre) is the cleanest accelerometer (≈ g). LSM (undamped, high-rate) needs the Known Defects corrections on Klagenfurt runs. RealSense (highest lever arm) is degraded/dead on several Mars runs.
• Respect the clocks. Fuse px4_gps, ground_truth_*, *_data_revised directly on the system clock; convert raw rtk_gps{1,2} by the per-run t_pximu_imugt first, or use the _data_revised lanes instead.
• Score on the real overlap window. ground_truth_8hz/80hz start after px4_imu, and ground_truth_80hz can end much earlier than the IMU span on the long and transition runs (Ground-Truth Products).
• Weight on reported quality.
  • Use rtk_status/gps_fix_type and the per-row covariances.
  • RTK σ from √cov, floored 1.4 cm/1.0 cm; PX4 GPS σ 0.8–4 m.
  • Reject cov_p > 1e12 PX4 rows outright.
• Replay in file order; treat t as approximate. Do not dedupe or reorder by timestamp. For images, key stereo pairs by _c1/_c2 + equal t[ns], verify file existence, and verify PNG decode: some referenced transition stereo pairs are absent on disk and one referenced transition_3 frame is zero-byte.
• Apply the corrections of Schema and Parsing and Known Defects at load time:
  • LSM accel ×1.5 on the five runs
  • LSM gyro bias removal on Klagenfurt
  • mag column un-swap on the _data family
  • headerless reads for _revised/px4_imu_data
  • duplicate-key YAML parse
• LRF. No camera↔︎LRF or LRF↔︎platform transform ships in any YAML (Camera-LRF Extrinsic). The boresight is essentially nadir / image-center; see Camera-LRF Extrinsic for the derived value and its uncertainty.
  • MaRS defines no LRF/range update — the LRF is recorded but not consumed by the estimator (it feeds the flight stack’s landing detector only).
• Reported usability benchmarks (paper).
  • MaRS EKF tracks transition_1 well with indoor vision-drift divergence
  • OpenVINS on mars_18 reaches ATE position 7.5 m / rotation 7° (Umeyama-aligned)