Oxford Spires

Oxford Spires Dataset (https://dynamic.robots.ox.ac.uk/datasets/oxford-spires): a hand-held/backpack VILENS payload walked around Oxford colleges.

A sequence is a directory containing raw/ros2bag/, under which the recording may be split across several ros2bag part directories. All parts must be replayed, or the run silently covers only a fraction of the ground truth. Part directories end in “_<n>”; they are ordered by that number, not lexicographically, so a sequence with ten or more parts still replays in order.

There is no /tf or /tf_static in these bags, so fixed sensor poses are mandatory. lidar_odometry_from_oxford_spires.yaml carries the same values as its defaults.

Those poses are in the dataset’s BASE frame, NOT the raw LiDAR frame, and the difference is a 180 deg yaw. Getting that wrong – placing the LiDAR at identity, as if base and lidar were the same frame – leaves every reported pose a body yaw away from the dataset’s own ground truth. APE hides it (a body yaw moves position only by the 0.124 m lever arm, and evo’s –align absorbs the rest); it negates the horizontal part of every RELATIVE motion, so vertical-drift and tilt metrics blow up. Symptom if it ever comes back: relative vertical drift in the tens-to-hundreds of mm/m on a run whose APE looks perfectly good.

T_base_lidar is sensor.yaml’s own value. T_base_imu is the LiDAR-frame IMU pose composed through it (T_base_lidar . T_lidar_imu), which reproduces sensor.yaml’s independently recorded T_base_imu to ~1 mm and 0.6 deg, so the two calibrations agree.

Number of OXFORD_SPIRES_BAG_N slots the launch YAML defines:

Running it

Online replay with the 3D GUI:

mola-lo-gui-oxford-spires /path/to/data/sequences/<sequence-name>/ [--headless] [additional flags]

Offline batch run, writing a trajectory file:

mola-lo-cli-oxford-spires /path/to/data/sequences/<sequence-name>/ [--headless] [additional flags]

What this profile sets, and why

These are defaults, not overrides: exporting any of these variables before running the wrapper takes precedence.

`MOLA_LIDAR_TOPIC`

Default: /hesai/pandar

`MOLA_IMU_TOPIC`

Default: /alphasense_driver_ros/imu

`MOLA_CAMERA_TOPIC`

Default: /alphasense_driver_ros/cam0/debayered/image/compressed

`MOLA_TF_BASE_LINK`

Default: base_link

`LIDAR_POSE_X`

Default: 0}" ; : "${LIDAR_POSE_Y:=0}" ; : "${LIDAR_POSE_Z:=0.124

`LIDAR_POSE_YAW`

Default: 180}" ; : "${LIDAR_POSE_PITCH:=0}" ; : "${LIDAR_POSE_ROLL:=0

`MOLA_USE_FIXED_LIDAR_POSE`

Default: true

`IMU_POSE_X`

Default: -0.018771

`IMU_POSE_Y`

Default: 0.008218

`IMU_POSE_Z`

Default: 0.053526

`IMU_POSE_YAW`

Default: 89.3737

`IMU_POSE_PITCH`

Default: -0.1665

`IMU_POSE_ROLL`

Default: -0.1287

`MOLA_USE_FIXED_IMU_POSE`

Default: true

`MOLA_LO_INITIAL_LOCALIZATION_METHOD`

Default: InitLocalization::PitchAndRollFromIMU

Handheld/backpack platform: lean on the IMU for the initial pitch/roll estimate and for deskewing, same as the ConSLAM wrapper. The Alphasense IMU does not publish an onboard-fused orientation (its Imu messages carry an all-zero quaternion), so the pitch/roll initializer automatically falls back to leveling from raw accelerometer readings.

`MOLA_DESKEW_METHOD`

Default: MotionCompensationMethod::IMU

Handheld/backpack platform: lean on the IMU for the initial pitch/roll estimate and for deskewing, same as the ConSLAM wrapper. The Alphasense IMU does not publish an onboard-fused orientation (its Imu messages carry an all-zero quaternion), so the pitch/roll initializer automatically falls back to leveling from raw accelerometer readings.

`MOLA_DESKEW_IGNORE_ACCELEROMETER`

Default: false

Keep the accelerometer in the deskew. This used to be suppressed, on evidence that gyro-only deskew cut path-length error and improved APE. Re-measured on all 13 sequences against today’s pipeline, both halves of that are gone: est/gt is identical to three decimals either way, and suppressing the accelerometer now COSTS about 11% of APE (median 0.886x in its favour, better on 9 of 13). The defect it compensated for has since been fixed elsewhere, so the override no longer earns its keep. Left explicit rather than deleted so the measurement is not lost.