Orb algorithm steps

1. How does ORB algorithm work?
2. Is ORB better than SIFT?
3. Is ORB rotation invariant?
4. Is ORB scale invariant?

How does ORB algorithm work?

ORB uses BRIEF descriptors but as the BRIEF performs poorly with rotation. So what ORB does is to rotate the BRIEF according to the orientation of keypoints. Using the orientation of the patch, its rotation matrix is found and rotates the BRIEF to get the rotated version.

Is ORB better than SIFT?

We showed that ORB is the fastest algorithm while SIFT performs the best in the most scenarios. For special case when the angle of rotation is proportional to 90 degrees, ORB and SURF outperforms SIFT and in the noisy images, ORB and SIFT show almost similar performances.

Is ORB rotation invariant?

ORB, a very fast binary descriptor based on BRIEF, which is rotation invariant and resistant to noise.

Is ORB scale invariant?

ORB features are invariant to scale, rotation and limited affine changes. S. Leutenegger et al. put forward Binary Robust Invariant Scalable Keypoints (BRISK) in 2011 [18], which detects corners using AGAST algorithm and filters them with FAST Corner score while searching for maxima in the scale space pyramid.