VI-Rig: 4 IMUs + 3 cameras

Demo and values

One MVIS camera + IMU run on recording april_01: every camera and all four IMUs solved together.

The scene MVIS recovered from this dataset, as on the homepage. The values beside it come from this page's run.

Reprojection median0.25 px

cam0–cam1 baseline71.0 mm

cam0 td−4.32 ms

cam0 lever arm91.6 mm

Reprojection is how far, in pixels, the detected corners lie from where the solve puts them. td is the camera–IMU time offset, and the lever arm is the camera–IMU position offset.

Calibration process

MVIS's own player, from this run: the detected board corners, then the rig's path as the solve refines it. Press Play or drag the bar; pick a camera card to look through that camera. We publish no camera images.

Solved rig

The solved positions and orientations, to scale in the IMU frame. Drag sideways to orbit. Tap a sensor to see its values.

3DFrontTopSide+−

Sensor	fx, fy, cx, cy px	Lever mm	log(R) rad	td ms	t_ga ms	Reprojection px
cam0	448.1, 447.5, 371.8, 280.9	[+32.6, −80.9, +27.9]	[+0.0031, −2.2167, +2.2213]	−4.32		0.294
cam1	286.8, 286.4, 415.7, 403.0	[+66.4, −111.0, −26.8]	[+0.0180, +2.2310, −2.2116]	−5.01		0.213
cam2	286.7, 286.2, 415.2, 397.4	[+2.5, −110.4, −26.7]	[−0.0255, −2.2259, +2.2122]	−7.68		0.226
IMU (base)		0	0	0	−0.28 ± 0.04
IMU gx3_25		[−122.5, −47.0, −3.2]	[+2.2382, +2.2040, −0.0239]	+0.00	+0.19 ± 0.03
IMU gx3_35		[−81.9, −47.2, −3.6]	[−2.2182, −2.2243, +0.0157]	−1.55	+0.15 ± 0.03
IMU t265		[+56.0, −107.2, −31.0]	[+1.5788, +0.0068, −0.0022]	+2.88	−6.62 ± 0.03

Lever arms and rotations are each sensor in the base IMU frame; rotation is log(R) in rad. td is the time offset to the base IMU, t_imu = t_sensor + td. Reprojection is the median per camera (all cameras: median 0.253 px): how well the model fits the corners, not how accurate it is.

Check against a reference

No published reference. No published calibration exists for this rig, so this page has nothing to compare against. What we can show is how much each value moves from one recording to the next. All 10 recordings and three tools: Dataset eval →

Config and run

virig_4imus_3cams_cam_imu.yaml

input:
  format: ros1
  path: virig_4imus_3cams_april_01.bag
  cam_topics:
  - /blackfly/image_raw
  - /t265/fisheye1/image_raw
  - /t265/fisheye2/image_raw
  imu_topics:
  - /imu/data
  - /gx3_25/data
  - /gx3_35/imu/data
  - /t265/imu
  window_mode: motion
  segment_length: 80.0
board:
  board_type: apriltag
  rows: 6
  cols: 6
  tag_size: 0.088
  tag_spacing: 0.3
  tag_family: t36h11
camera_input:
  path: mvis_4imus_3cams_calib.yaml
  cameras:
  - {}
  - factor_hz: 4.0
  - factor_hz: 4.0
solve:
  max_iterations: 40
  corner_subsample: two_anti
  sigma_g: 0.00065
  sigma_a: 0.0026
  sigma_bg: 0.001
  sigma_ba: 0.002
estimate:
  board_points: true
  camera:
    intrinsics: true
    tr: false
    td: true
    extrinsics: true
  imu:
    intrinsics: dw_da
    model: calyx
    extrinsics: true
    td: true
output:
  path: cam_imu.json

shell

mvis cam-imu -c virig_4imus_3cams_cam_imu.yaml

The marked lines are the choices that matter for this rig:

• input.imu_topics: Four IMU topics. The first is the base IMU; the other three are solved against it.
• input.window_mode: MVIS picks the 80 s window with the most motion.
• camera_input.cameras: The two T265 cameras are added to the graph at 4 Hz, which keeps the solve small.
• solve.sigma_g: IMU noise from a still recording of this rig, measured density × 2.5. The other three sigmas are set the same way.
• estimate.board_points: The printed board is not quite flat, so its shape is estimated too.
• estimate.camera.intrinsics: Camera intrinsics stay free in the camera + IMU solve.

This is the config of the run on this page, with every path cut to its file name. Point the paths at your copy.

The solve took about 13 min on one desktop. It writes cam_imu.json, a calibration YAML and a report beside the config.

MVIS

MVIS main, measured-noise batch of 2026-11-08

Run date

2026-11-08

Data

VI-Rig 4 IMUs + 3 cams dataset page →

Config

virig_4imus_3cams_cam_imu.yaml, above

Command

mvis cam-imu -c virig_4imus_3cams_cam_imu.yaml

Dataset

• Recording april_01, one of the 10 recordings of this rig. MVIS picks the 80 s window with the most motion.
• Cameras: a Blackfly S (pinhole with radial-tangential distortion) and the two T265 fisheye cameras (equidistant lens model).
• IMUs: the Xsens MTi is the base IMU; the two MicroStrain units and the T265's own IMU are solved against it.
• Board: AprilGrid 6×6, tag 88 mm, spacing 0.3, t36h11.
• Solve window: 80.0 s.

Download: VI-Rig 4 IMUs + 3 cams dataset page → The recordings are listed there, not copied here.

AprilGrid 6 × 6, 660 × 660 mm. Standard pattern, to scale