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intelrealsense-d435i-calibration.md

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description
Calibration of IntelRealSenseD435i using AprilGrid

IntelRealSense D435i Calibration

Installing Kalibr

Building Kalibr from Source

  1. Install the necessary dependencies:

    sudo apt-get install -y git wget autoconf automake nano libeigen3-dev libboost-all-dev libsuitesparse-dev doxygen libopencv-dev libpoco-dev libtbb-dev libblas-dev liblapack-dev libv4l-dev python3-dev python3-pip python3-scipy python3-matplotlib ipython3 python3-wxgtk4.0 python3-tk python3-igraph python3-pyx

  2. Create and configure a workspace:

    mkdir -p ~/kalibr_workspace/src
cd ~/kalibr_workspace
export ROS1_DISTRO=noetic # Replace 'noetic' with your ROS version
source /opt/ros/$ROS1_DISTRO/setup.bash
catkin init
catkin config --extend /opt/ros/$ROS1_DISTRO
catkin config --cmake-args -DCMAKE_BUILD_TYPE=Release

  3. Clone the Kalibr project and build it:

    cd ~/kalibr_workspace/src
git clone https://github.com/ethz-asl/kalibr.git
cd ~/kalibr_workspace/
catkin build -DCMAKE_BUILD_TYPE=Release -j4

    Source the workspace setup:

    source ~/kalibr_workspace/devel/setup.bash

Recording a Rosbag

To record a rosbag, follow these steps:

  1. Start ROS using the command:

    roscore

  2. Install the IntelRealSense ROS package for your ROS distribution:

    sudo apt-get install ros-$ROS_DISTRO-realsense2-camera
source devel/setup.bash

  3. Launch the camera node using:

    roslaunch realsense2_camera rs_camera.launch

  4. Check that camera topics are listed with:

    rostopic list

    You should see topics such as camera/color/image_raw.

  5. Record a rosbag from all topics:

    rosbag record -a

    Press Ctrl+C to stop recording. The rosbag will be saved in the current directory.

    Important points during recording:

    • Excite all IMU axes (rotation and translation).
    • Avoid shocks, especially at the beginning and end of recording.
    • Maintain low motion blur through low shutter times and good illumination.
    • Ensure timestamps have low jitter and are synchronized.

  6. Check the rosbag info and play it using:

    rosbag info
rosbag play

Calibrating the Camera Using AprilGrid

  1. Ensure the AprilGrid details are specified in a .yaml file.

  2. To calibrate the camera, run the following command in the directory containing the .yaml file and rosbag:

    rosrun kalibr kalibr_calibrate_cameras --target [name of .yaml file] --models [camera/distortion models to be fitted] --topics [name of topic where image from camera is being published] --bag [path to rosbag] --bag-freq 10.0 --show-extraction

    Notes:

    • The camera distortion model used should be pinhole-radtan.
    • The --show-extraction flag shows the calibration alongside the feed.
    • The --bag-freq 10.0 sets the playback frequency of the rosbag to 10 Hz during calibration.

The results of the calibration process will be saved in a PDF and the matrix parameters will be stored in a .yaml file in the same directory.