Reprojection Error too High in Visual Odometry

C++
1

Hi everyone! I’m workin on my Mono Visual Odometry project. During the triangulation step, i’m trying to compute the reprojection error. However, the value is too high and I don’t know why.
This is my function for reprojection error:

vector<double> reproject_error(Mat world_points, Mat R, Mat t, Mat cameraMatrix, vector<Point2f> img_points)
{

    /************************REPROJECT ERROR*********************************
     * world_points: Punti 3D in coordinate {W} da proiettare in {C}.       *
     * R e t: Trasformazione omogenea che trasforma da {W} a {C}            *
     * cameraMatrix                                                         *
     * img_points: Punti con cui confrontare i world_points riproiettati.   *
     ************************************************************************/

    //Reproject world_points (3D) in 2D image plan, using projectPoints
    Mat reproject_points;
    Mat Rvec;
    Rodrigues(R, Rvec);

    projectPoints(world_points, Rvec, t, cameraMatrix, noArray(), reproject_points); 

    //Compute reproject error
    vector<double> reproject_err(img_points.size());

    for(int i = 0; i < reproject_point.rows; i++)
    {
        ROS_INFO("Keypoint 2D: [%f, %f] \t Reprojected World Point: [%f, %f]", img_points[i].x, img_points[i].y, reproject_points.at<double>(i, 0), reproject_points.at<double>(i, 1));
        reproject_err[i] = sqrt(pow(img_points[i].x - reproject_point.at<double>(i, 0), 2.0) + pow(img_points[i].y - reproject_points.at<double>(i, 1), 2.0));
    }
    ROS_INFO("----------------------");

    return reproject_err;
}
2

Hi @Elektron97

Code seems fine. I see you don’t provide distortion coefficients, why?
Remember, errors are in pixel units.
It is a common mistake to provide the wrong R and t, from camera to world transformation.

1 Like
3

Thank you for your answer.
For distortion coefficients: I’m working with a simulate camera with 0 distortion coefficients.
Yes, it’s probabily a wrong usage of triangulatePoints(). Thank you!