IDs of April Tags

Development Asset Creation
1

Hey!

I’m using RealityCapture to scan a scene with some april tags. In the future application, I need to compute the pose of a webcam by again finding the april tags and using OpenCV with the known positions.

My problem is now that with my april-tag library, I get different IDs of the markers than with RealityCapture. I create some 36h11-markers with IDs from 1 to 10, but read completely different values. If found a somehow official Apriltag-repo here: GitHub - AprilRobotics/apriltag-imgs: Pre-generated AprilTag images and the images there do not fit to the tags created by RC.

Any ideas how this can happen? Is there a documentation which april-tag library is used within RC?

2

Hi NikolasMunich,
we have our own implementation, so differences are possible. They seem to be using a different numbering scheme. Ours is quite natural, we order the payloads in ascending order, so the first is 0x0110bba61 and the last is 0xfece0e599 (if you were to print all 587 of them).

3

Thanks for the fast answer!
So you mean you deviate from the coding scheme that was published here: AprilTag ?

4

Technically yes, it is different.

5

Ok. I think the april tags are a really nice feature, but to be honest, it’s not a great design to use the ‘April-tag’ name, and even the 36h11-naming scheme and then use a new code. That’s just provoking confusion and a mixup in the codes. Some people already have printed april tags and I think coding should be kept consistent with what was published under the name.

6

Yes, I understand to that.
I will create a feature request for this for our developers to implement/change the target creation tool.
I am sorry for the inconveniences.

1 Like
7

That would be great! The markers are really useful, but with a consistent naming scheme, it would be easier to use.

8

I also struggle with this issue, and I made a script to analyze the 36h11 family (that’s what I use), and made a lookup table to post here for anyone else who needs them.

I understand that changing the ID’s could break many systems using RC, so even a look up table like this would be nice.

Summary
RC_Tag_Label Official_AprilTag_ID
1 476
2 283
3 296
4 208
5 246
6 510
7 172
8 6
9 530
10 138
11 161
12 237
13 558
14 418
15 393
16 176
17 443
18 394
19 515
20 577
21 166
22 349
23 392
24 206
25 123
26 249
27 187
28 302
29 250
30 297
31 403
32 538
33 422
34 528
35 156
36 493
37 131
38 429
39 547
40 447
41 7
42 364
43 442
44 361
45 152
46 359
47 210
48 572
49 417
50 570
51 333
52 372
53 56
54 427
55 68
56 189
57 502
58 197
59 108
60 178
61 46
62 179
63 120
64 581
65 94
66 313
67 245
68 279
69 220
70 281
71 74
72 153
73 223
74 196
75 523
76 477
77 472
78 353
79 580
80 199
81 126
82 318
83 326
84 8
85 585
86 300
87 95
88 525
89 351
90 146
91 182
92 9
93 278
94 47
95 254
96 345
97 369
98 501
99 396
100 171
101 147
102 231
103 192
104 317
105 517
106 173
107 483
108 582
109 452
110 362
111 426
112 267
113 358
114 31
115 48
116 514
117 474
118 298
119 390
120 242
121 568
122 508
123 282
124 268
125 57
126 416
127 532
128 583
129 142
130 98
131 507
132 473
133 10
134 482
135 439
136 526
137 75
138 461
139 512
140 360
141 543
142 563
143 324
144 397
145 381
146 356
147 574
148 87
149 395
150 150
151 544
152 375
153 490
154 391
155 575
156 11
157 379
158 562
159 49
160 387
161 129
162 467
163 12
164 32
165 454
166 541
167 478
168 487
169 430
170 485
171 534
172 165
173 553
174 13
175 571
176 524
177 203
178 376
179 434
180 469
181 307
182 99
183 253
184 135
185 175
186 137
187 69
188 303
189 305
190 215
191 89
192 520
193 109
194 494
195 14
196 560
197 70
198 216
199 90
200 559
201 100
202 334
203 321
204 15
205 119
206 259
207 573
208 465
209 76
210 365
211 564
212 308
213 304
214 540
215 513
216 262
217 271
218 33
219 316
220 521
221 224
222 408
223 536
224 260
225 475
226 16
227 537
228 241
229 80
230 145
231 202
232 77
233 169
234 471
235 83
236 557
237 503
238 234
239 136
240 159
241 124
242 280
243 180
244 211
245 141
246 274
247 289
248 34
249 264
250 185
251 336
252 71
253 425
254 101
255 441
256 158
257 17
258 35
259 401
260 448
261 322
262 140
263 276
264 535
265 214
266 18
267 36
268 58
269 290
270 511
271 96
272 37
273 389
274 263
275 286
276 181
277 522
278 116
279 59
280 186
281 459
282 188
283 81
284 332
285 542
286 411
287 113
288 339
289 50
290 121
291 78
292 410
293 457
294 240
295 398
296 419
297 266
298 342
299 195
300 127
301 84
302 384
303 371
304 565
305 19
306 184
307 367
308 498
309 421
310 584
311 167
312 314
313 481
314 191
315 20
316 550
317 458
318 257
319 293
320 151
321 190
322 435
323 226
324 164
325 440
326 21
327 51
328 354
329 311
330 229
331 91
332 415
333 60
334 350
335 233
336 567
337 506
338 309
339 285
340 446
341 106
342 491
343 22
344 38
345 52
346 61
347 248
348 405
349 130
350 227
351 552
352 272
353 386
354 148
355 366
356 62
357 373
358 275
359 468
360 480
361 489
362 566
363 122
364 451
365 341
366 432
367 128
368 157
369 102
370 288
371 174
372 258
373 222
374 368
375 531
376 299
377 284
378 273
379 97
380 295
381 103
382 400
383 579
384 200
385 464
386 132
387 219
388 556
389 287
390 23
391 39
392 505
393 53
394 218
395 377
396 125
397 291
398 551
399 413
400 24
401 154
402 412
403 527
404 144
405 402
406 518
407 63
408 72
409 277
410 466
411 463
412 88
413 420
414 92
415 470
416 492
417 294
418 545
419 444
420 569
421 496
422 555
423 104
424 212
425 117
426 319
427 25
428 40
429 549
430 504
431 64
432 149
433 331
434 168
435 228
436 388
437 423
438 193
439 244
440 431
441 118
442 26
443 205
444 160
445 329
446 374
447 548
448 194
449 533
450 352
451 162
452 407
453 239
454 255
455 27
456 320
457 65
458 66
459 139
460 252
461 143
462 437
463 399
464 346
465 41
466 155
467 261
468 509
469 85
470 462
471 484
472 236
473 105
474 54
475 497
476 460
477 163
478 221
479 433
480 310
481 330
482 115
483 561
484 347
485 357
486 378
487 406
488 306
489 312
490 213
491 450
492 55
493 488
494 344
495 343
496 404
497 28
498 42
499 456
500 232
501 265
502 170
503 363
504 110
505 500
506 0
507 217
508 207
509 29
510 486
511 335
512 516
513 67
514 133
515 114
516 1
517 43
518 325
519 230
520 578
521 414
522 315
523 107
524 134
525 2
526 382
527 546
528 111
529 380
530 201
531 539
532 238
533 3
534 30
535 44
536 251
537 438
538 499
539 529
540 204
541 453
542 177
543 292
544 338
545 586
546 554
547 383
548 79
549 86
550 93
551 243
552 576
553 370
554 348
555 4
556 409
557 436
558 495
559 73
560 82
561 355
562 198
563 327
564 455
565 519
566 209
567 270
568 247
569 256
570 5
571 428
572 449
573 323
574 424
575 340
576 445
577 235
578 337
579 225
580 183
581 45
582 301
583 328
584 269
585 385
586 112
587 479