Error, more than one new minima found

[allsey87]

Regarding the fprintf in apriltag_pose.c:435 that prints:

Error, more than one new minima found

How is a user of your library supposed to react to this message? Is this a bug or is it debugging output that can be safely ignored? In the latter case, perhaps this debugging output can be toggled on and off using a member of the apriltag_detection_info_t?

[hwscut]

When seeing more than one tag to estimate tag_pose, I also get such error. Getting this error, the estimated poses cannot be used, so i think it is a bug in codes. waitting for solution.

[zftan0709]

Tag ID: 10
Normalized： 
-1.76278 -0.31017
Translation: 
4.97972  -0.959973 -2.89562
Rotation: 
-0.928616 0.175963 -0.326666
0.13727 0.980855 0.138131
-0.344717 -0.0834289 0.934992

Error, more than one new minimum found.

Tag ID: 10
Normalized： 
-1.76919 -0.31115
Translation: 
-5.06095  0.973719 2.93369
Rotation: 
-0.156745 -0.142866 0.977251
0.0681974 -0.988686 -0.133599
0.985282 0.0457049 0.164715

I'm having the same problem and the Tz changes to negative from time to time.

[C-monC]

Hi,

I get this error with only one tag in the image. Did anyone figure out the reason for this error?

[wxmerkt]

Can you provide a test image where this happens?

[mpillet]

Can we reopen this issue please ? I'm facing the same problem with 'Error, more than one new minima found' leading to a wrong reconstruction. Here is an example where the detection of the tag works but with this error of more than one new minima found.

[christian-rauch]

Can we reopen this issue please ?

I think this issue was never closed. So no worries there :-)

I'm facing the same problem with 'Error, more than one new minima found' leading to a wrong reconstruction. Here is an example where the detection of the tag works but with this error of more than one new minima found.

Is this reproducible with the apriltag_demo? Can you provide a jpeg image and potential command-line arguments that cause the issue with the apriltag_demo?

[ggb367]

Hi @christian-rauch, we're also running into this multiple minima error with this image when estimating the pose of each of the tags: Usually one minima is correct while the other is quite incorrect. We tried to see if we could reproduce the error with aprilrtag_demo with: ./apriltag_demo -f tagStandard52h13 -i 10 ./image_raw.jpg But we don't see a way to estimate the pose with that script. Let me know if I can provide any additional details to figure this issue out. Thanks!

[christian-rauch]

We tried to see if we could reproduce the error with aprilrtag_demo with: ./apriltag_demo -f tagStandard52h13 -i 10 ./image_raw.jpg But we don't see a way to estimate the pose with that script.

Thanks for sharing the example image. The apriltag_demo executable only does the tag detection without the pose estimation.

Let me know if I can provide any additional details to figure this issue out. Thanks!

Can you also provide the camera intrinsics used for the pose estimation? Is the code you use publicly available?

[ggb367]

Is the code you use publicly available?

The repository is not public, but I can share code snippets as needed

Can you also provide the camera intrinsics used for the pose estimation?

See below:

image_width: 640
image_height: 480
camera_name: narrow_stereo
camera_matrix:
  rows: 3
  cols: 3
  data: [661.97625,   0.     , 313.69227,
           0.     , 661.02677, 257.01043,
           0.     ,   0.     ,   1.     ]
distortion_model: plumb_bob
distortion_coefficients:
  rows: 1
  cols: 5
  data: [0.054322, -0.183210, 0.001954, -0.002335, 0.000000]
rectification_matrix:
  rows: 3
  cols: 3
  data: [1., 0., 0.,
         0., 1., 0.,
         0., 0., 1.]
projection_matrix:
  rows: 3
  cols: 4
  data: [662.69727,   0.     , 312.00752,   0.     ,
           0.     , 662.65527, 257.08592,   0.     ,
           0.     ,   0.     ,   1.     ,   0.     ]

[christian-rauch]

I tried reproducing this by calling estimate_tag_pose on the detections in the apriltag_demo.c on the current master (51466ec524d9a5d7b759f42663e5da9810ff5261):

#include "apriltag_pose.h"
...
for (int i = 0; i < zarray_size(detections); i++) {
    apriltag_detection_t *det;
    zarray_get(detections, i, &det);

    if (!quiet)
        printf("detection %3d: id (%2dx%2d)-%-4d, hamming %d, margin %8.3f\n",
                i, det->family->nbits, det->family->h, det->id, det->hamming, det->decision_margin);

    hamm_hist[det->hamming]++;
    total_hamm_hist[det->hamming]++;

    // pose estimation
    apriltag_detection_info_t info;
    info.det = det;
    info.tagsize = 0.05;
    info.fx = 661.97625;
    info.fy = 661.02677;
    info.cx = 313.69227;
    info.cy = 257.01043;
    apriltag_pose_t pose;
    estimate_tag_pose(&info, &pose);
    printf("  >> posistion: %f %f %f\n", pose.t->data[0], pose.t->data[1], pose.t->data[2]);
}

This gives me 8 detections with a pose (just printing position here):

detection   0: id (52x13)-4   , hamming 0, margin  141.337
  >> posistion: 0.043182 -0.045479 1.442508
detection   1: id (52x13)-6   , hamming 0, margin  151.679
  >> posistion: -0.064532 -0.246879 1.471909
detection   2: id (52x13)-7   , hamming 0, margin  141.630
  >> posistion: -0.066965 -0.143569 1.462468
detection   3: id (52x13)-8   , hamming 0, margin  158.549
  >> posistion: 0.145398 -0.044111 1.447844
detection   4: id (52x13)-10  , hamming 0, margin  147.847
  >> posistion: 0.036983 -0.148168 1.462753
detection   5: id (52x13)-11  , hamming 0, margin  148.997
  >> posistion: 0.144882 -0.143754 1.466733
detection   6: id (52x13)-12  , hamming 0, margin  157.467
  >> posistion: 0.137947 -0.247066 1.487945
detection   7: id (52x13)-14  , hamming 0, margin  145.122
  >> posistion: -0.060477 -0.038616 1.433352
detection   8: id (52x13)-16  , hamming 0, margin  153.694
  >> posistion: 0.036604 -0.253608 1.481749

I am using the camera parameters from the camera_matrix above and guessed the tag size to be 5cm. I built in debug mode so that debug_print will print to stderr (otherwise this will be silent), but I don't see the "Error, more than one new minimum found. message on the screen.

@ggb367 Can you add this to the apriltag_demo as well, update the tag size and camera parameters if needed and also tell me the remaining missing parameters to reproduce this issue?

[christian-rauch]

Since there is no feedback on this, I assume that the issue has been resolved on your side. If it still persists, please reopen with more information to reproduce the issue.