binbin-xu/yac

YAC - Yet Another Calibrator

YAC - Yet Another Calibrator

Yet Another Calibrator (YAC) is a calibration tool for calibrating RGB cameras. Specifically:

• Camera intrinsics
• Stereo camera intrinsics and extrinsics
• Mocap-marker to camera extrinsics

Supported projection-distortion models:

• pinhole-radtan4
• pinhole-equi4

Dependencies

# Ubuntu packages
libyaml-cpp-dev
libeigen3-dev
libceres-dev
libopencv-dev
libomp-dev (optional)

# Custom (see deps dir)
Modified apriltag3 (https://github.com/AprilRobotics/apriltag)
Modified apriltags (https://github.com/chutsu/apriltags)

Build

For the lazy :

# The following assumes you have a catkin workspace at $HOME/catkin_ws
# If not edit the CATKIN_WS variable in the Makefile

git clone https://github.com/chutsu/yac
cd yac
make deps
make release

Or standard approach:

# Clone repo to your catkin workspace
cd <your catkin workspace>/src
git clone https://github.com/chutsu/yac

# Install dependencies
cd yac && make deps

# Build yac
catkin build -DCMAKE_BUILD_TYPE=Release yac yac_ros
# Note: Optimization will be very slow if not built in RELEASE mode.

Calibration Target

yac uses a grid of AprilTags, a.k.a an AprilGrid, as a calibration target.

Click here to download and print the AprilGrid. During data collection make sure the calibration target is as flat as possible.

Calibrate Camera Intrinsics or Stereo Intrinsics and Extrinsics

First inorder to calibrate a monocular camera or stereo camera pair we need to create the calibration configuration file. For example calib_intel_d435i.yaml configuration file:

ros:
  bag: "/data/intel_d435i/imucam-1.bag"
  cam0_topic: "/stereo/camera0/image"

calib_target:
  target_type: 'aprilgrid'  # Target type
  tag_rows: 6               # Number of rows
  tag_cols: 6               # Number of cols
  tag_size: 0.088           # Size of apriltag, edge to edge [m]
  tag_spacing: 0.3          # Ratio of space between tags to tagSize
                            # Example: tag_size=2m, spacing=0.5m
                            #          --> tag_spacing=0.25[-]

cam0:
  proj_model: "pinhole"
  dist_model: "radtan4"
  lens_hfov: 69.4
  lens_vfov: 42.5
  resolution: [640.0, 480.0]
  rate: 30.0

cam1:
  proj_model: "pinhole"
  dist_model: "radtan4"
  lens_hfov: 69.4
  lens_vfov: 42.5
  resolution: [640.0, 480.0]
  rate: 30.0

The above tells yac where to find the rosbag containing the calibration data, the calibration target and camera details. Now, we need to pass that to a yac calibrator via the roslaunch file calib_mono.launch or calib_stereo.launch:

# To calibrate cam0 intrinsics only
roslaunch yac calib_mono.launch config_file:=<path to calib_intel_d435i.yaml>

# To calibrate stereo camera pair intrinsics and extrinsics
roslaunch yac calib_stereo.launch config_file:=<path to calib_intel_d435i.yaml>

LICENCE

MIT