By Dheeraj Kamath, Diganth P, Balaji and Harshith J Shiva

ArUco markers are binary square fiducial markers that can be used for camera pose estimation. Their main benefit is that their detection is robust, fast and simple.

An ArUco marker is a synthetic square marker composed by a wide black border and a inner binary matrix which determines its identifier (id). The black border facilitates its fast detection in the image and the binary codification allows its identification and the application of error detection and correction techniques. The marker size determines the size of the internal matrix. For instance, a marker size of 4x4 is composed by 16 bits.

The first, third and fifth columns represent parity bits. The second and fourth columns represent the data bits.

Divide the resulting image into a 5x5 grid and check the color in each cell of the second and fourth columns(in that order) in a top to bottom manner.

This is how the id of the marker is determined.

Image processing of ArUco markers using raspberry pi