[ros-users] [Discourse.ros.org] [General] Fiducial Marker Based Localization System - Package Annoucement

David Crawley ros.discourse at gmail.com
Wed Feb 28 04:52:25 UTC 2018



Yes we have characterized the accuracy as Rohan says in normal conditions its good to a couple cm. Our system dynamically computes the accuracy based on the accuracy of all the markers it can see and combines the poses from all the visible markers in making its estimate. If you increase the density of markers the accuracy will improve but it is a n^0.5 process. Moving markers closer to the robot will also increase accuracy as will increasing their size.

Its important to note that the size of the fiducial can be determined both in principle and practice to less than 1 pixel, based on fitting lines to the edge of the aruco marker square, a pattern that crosses many pixels. Signal to noise and sensible lighting is important to get decent results here.

The results that we are getting are good for most of the applications we use, that doesn't mean we aren't going to continue to improve it. The things that are on the list of proposed improvements include:

- Estimate pose from all the fiducials simultaneously rather than independently computing pose and combining them (as already discussed by Rohan)
- Automatically optimizing camera exposure parameters to maximize accuracy
- Automatically optimizing aruco parameters to maximize accuracy given computational constraints (you can improve accuracy by doing more fitting computations at the expense of computer cycles)
- Automatically optimizing camera calibration data based on the large amount of data that's available from looking at many fiducials - each fiducial is a bit like a checker board (calibration board) so you should be able to get better results from driving around and looking at many fiducials than from the relatively small amount of data available from a normal camera calibration. This is actually really important for a whole host of reasons not least that manufacturing variances between robots can get frictionlessly calibrated away with the user not having to do anything other than navigate and drive. The improvement also spills over in to other uses of the camera.
- and many many more.....

We will of course continue to work on refining this package, but its always great to get the input, ideas and most importantly code commits from the broader community to make this software better.





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