CameraCalibration

Camera calibration parameters

Panel support

Schema

fieldtypedescription
timestamptimeTimestamp of calibration data
frame_idstringFrame of reference for the camera. The origin of the frame is the optical center of the camera. +x points to the right in the image, +y points down, and +z points into the plane of the image.
widthuint32Image width
heightuint32Image height
distortion_modelstringName of distortion model
Dfloat64[]Distortion parameters
Kfloat64[9]Intrinsic camera matrix (3x3 row-major matrix)
Rfloat64[9]Rectification matrix (3x3 row-major matrix)
Pfloat64[12]Projection/camera matrix (3x4 row-major matrix)

K

A 3x3 row-major matrix for the raw (distorted) image.

Projects 3D points in the camera coordinate frame to 2D pixel coordinates using the focal lengths (fx, fy) and principal point (cx, cy).

    [fx  0 cx]
K = [ 0 fy cy]
    [ 0  0  1]

R

A rotation matrix aligning the camera coordinate system to the ideal stereo image plane so that epipolar lines in both stereo images are parallel.

P

    [fx'  0  cx' Tx]
P = [ 0  fy' cy' Ty]
    [ 0   0   1   0]

By convention, this matrix specifies the intrinsic (camera) matrix of the processed (rectified) image. That is, the left 3x3 portion is the normal camera intrinsic matrix for the rectified image.

It projects 3D points in the camera coordinate frame to 2D pixel coordinates using the focal lengths (fx', fy') and principal point (cx', cy') - these may differ from the values in K.

For monocular cameras, Tx = Ty = 0. Normally, monocular cameras will also have R = the identity and P[1:3,1:3] = K.

For a stereo pair, the fourth column [Tx Ty 0]' is related to the position of the optical center of the second camera in the first camera's frame. We assume Tz = 0 so both cameras are in the same stereo image plane. The first camera always has Tx = Ty = 0. For the right (second) camera of a horizontal stereo pair, Ty = 0 and Tx = -fx' * B, where B is the baseline between the cameras.

Given a 3D point [X Y Z]', the projection (x, y) of the point onto the rectified image is given by:

[u v w]' = P * [X Y Z 1]'
       x = u / w
       y = v / w

This holds for both images of a stereo pair.

Reference implementations

Foxglove schemas are framework-agnostic, and can be implemented using any supported message encoding:

encodingschema name
ROS 1foxglove_msgs/CameraCalibration
ROS 2foxglove_msgs/msg/CameraCalibration
JSONfoxglove.CameraCalibration
Protobuffoxglove.CameraCalibration

You must use the schema names specified above for Foxglove Studio to recognize the schema.