# How many AR markers should I use to get the object pose?

I'd like to get the object pose based on the attached AR marker to the object. I believe I only need one tag to get the 6D pose. However, I sometimes see more than one AR markers are used in the research papers or the demos by Boston Dynamics (https://boygeniusreport.files.wordpress.com/2016/02/screenshot-76.png) or by the team at Amazon Robotics Challenge.

Do I need to use more than one marker? If so, how can I calculate the 6D pose from more than one marker's information?

• Correct, you can get the information you need with one ArUco marker. We have performed automatic landing of multirotors using a large single marker. If you would like to utilize a marker map with rigidly defined 3D geometry, you can just use the library, which uses OpenCV's solvePnPRansac under the hood. If you want to use disparate markers like in the Boston Dynamics image, you will have to do some sort of averaging, which is simple for translation but requires more finesse for the orientation. – Parker Lusk Sep 13 '17 at 4:02
• I'm using solvePnP. Do you think solvePnPRansac is better for the pose estimation from an ArUco marker rather than solvePnP? – kangaroo Sep 13 '17 at 19:59
• It depends on your geometry and exactly what you are trying to do. Use solvePnPRansac if you have noisy points / possibly incorrect 2d to 3d correspondences. – Parker Lusk Sep 13 '17 at 23:54