angle inversion of the marker

[fres]

Hello, I have a problem when putting a mark on the head of a robot. If the robot is to much turned on the right or the left, the Z axis become inverted ( it is not a flip, this wrong position stay for around 20 degres then become reinverted into the right rotation ). The strange thing is that it is not happening when doing a whole turn with a mark on the ground...

I write a question with more details and photos in ros answers :
http://answers.ros.org/question/207993/unwanted-rotation-of-the-markers-detected-with-ar_track_alvar/

If anyone has an idea?

[fres]

OK it is my mistake, my calibration file wasn't good enough