What are the advantages / disadvantages between the different predefined ArUco dictionaries?

Question

I want to use ArUco markers to detect objects and use a predefined dictionary.

I only need a small amount of different markers. About 10. I am now wondering what the advantages and disadvantages are between the different predefined dictionaries.

Dictionaries differ in amount of markers and bit size.

My thoughts so far:

• Having a lower amount of markers decreases the inter marker distance, thus the chance of faulty marker ID classification. However, the maximum amount of available unique markers is lower.

• Having a lower bit size helps to identify the markers better if their pixel size in the captured image is small (marker are printed small / far away in image). However, the maximum amount of available unique markers is lower.

Is my thought process so far correct? Did I miss anything?

So for me, only needing 10 different markers, I probably should stick to the DICT_4X4_50 dictionary to achieve best marker detection results?!

Or would it even be better to create my own dictionary with even less markers to increase inter marker distance?

Answer 1

I am the main ArUco developer. I personally recommend the first 10 markers of the ARUCO_MIP_36h12 dictionary. Unless you are working at an extremely low resolution, there is no real improvement in working with small markers such as 4x4 or 3x3. This is because internally the library reduces the detected marker to a small size (of around 50x50 bits regardless its dimensions in the actual image) and it is in this resolution in which the code is analyzed.

The fully explained pipeline of the ArUco library is described in the latest paper https://www.researchgate.net/publication/325787310_Speeded_Up_Detection_of_Squared_Fiducial_Markers in Sect 3.2. Also, you can have more information in the documentation at https://docs.google.com/document/d/1QU9KoBtjSM2kF6ITOjQ76xqL7H0TEtXriJX5kwi9Kgc