I have noticed that there are different types of fiducial markers on Preseverance.
While I have seen the round markers on other rovers before, it is the first time that I see the rectengular markers. Of course this does not mean, that earlier rovers did not use them.
However, I wonder why there are different markers at all. I thought these markers would be used to calibrate the cameras, help to measure positions, orientations, distances, etc. But the rectengular markers look like AprilTags (are they?).
Do these different tags serve different purposes?
The picture is a screenshot from a NASA video I found on Twitter: https://twitter.com/NASA/status/1363940380346118144/video/1