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Datasets and Calibration Targets

  1. The PDF file of Aprilgrid 6x6

  2. Camera calibration targets: april_6x6.yaml

target_type: 'aprilgrid' #gridtype
tagCols: 6               #number of apriltags
tagRows: 6               #number of apriltags
tagSize: 0.0025           #size of apriltag, edge to edge [m]
tagSpacing: 0.3          #ratio of space between tags to tagSize
codeOffset: 0            #code offset for the first tag in the aprilboard






  1. The following file (cam_april-camchain.yaml) will be generated automatically from camera calibration and required by camera and IMU calibration:
cam0:
  cam_overlaps: []
  camera_model: pinhole
  distortion_coeffs: [-0.2879529995338575, 0.0781311194952221, 0.00021265916642721963, -0.0001221450347654466]
  distortion_model: radtan
  intrinsics: [458.9432286546919, 457.5637533402653, 367.0272509347057, 249.3128033381081]
  resolution: [752, 480]
  rostopic: /cam0/image_raw
  1. IMU specification file imu.yaml:
#Accelerometers
accelerometer_noise_density: 0.00098   #Noise density (continuous-time)
accelerometer_random_walk:   0.00055   #Bias random walk

#Gyroscopes
gyroscope_noise_density:     6.981317007977319e-05   #Noise density (continuous-time)
gyroscope_random_walk:       0.00020   #Bias random walk

rostopic:                    /imu0      #the IMU ROS topic
update_rate:                 200      #Hz (for discretization of the values above)

it is recommended to obtain values for this file from: allan_variance_ros, otherwise read this page

Refs: 1, 2

Supported Camera Models and Distortion

'pinhole-radtan', 'pinhole-equi', 'pinhole-fov', 'omni-none', 'omni-radtan', 'eucm-none', 'ds-none'

Refs: 1

Camera Calibration

clone the repository:

git clone [email protected]:ethz-asl/kalibr.git

Then build the docker image"

cd kalibr
docker build Dockerfile_ros1_20_04

place your files (recording bag file cam_april.bag, imu.yaml and april_6x6.yaml ) in directory:

FOLDER=<path-to-data-directory>

Then run the following:

xhost +local:root
docker run -it -e "DISPLAY" -e "QT_X11_NO_MITSHM=1" \
    -v "/tmp/.X11-unix:/tmp/.X11-unix:rw" \
    -v "$FOLDER:/data" kalibr

Now in the container (for normal cameras):

source devel/setup.bash
rosrun kalibr kalibr_calibrate_cameras     --bag /data/cam_april.bag --target /data/april_6x6.yaml     --models pinhole-radtan --topics /cam0/image_raw

for fish-eye lenses:

source devel/setup.bash
rosrun kalibr kalibr_calibrate_cameras     --bag /data/cam_april.bag --target /data/april_6x6.yaml     --models pinhole-equi --topics /cam0/image_raw

Camera IMU Calibration

source devel/setup.bash
rosrun kalibr kalibr_calibrate_imu_camera --bag /data/cam_april.bag --cam  /data/cam_april-camchain.yaml  --imu  /data/imu.yaml  --target /data/april_6x6.yaml

Refs: 1