apriltag Pose w.r.t center of tag or top left corner? about apriltag_ros HOT 3 CLOSED

@m0oz @wxmerkt in this document it is written like https://doc.rc-visard.com/latest/en/tagdetect.html

The z-axis is pointing “into” the tag. Please note that for AprilTags, although having the white border included in their definition, the coordinate system’s origin is placed exactly at the transition from the white to the black border. Since AprilTags do not have an obvious orientation, the origin is defined as the upper left corner in the orientation they are pre-generated in.

so it should be upper left corner? or, in /tag_detections_image we can see center of tag in image_view?

can anyone help?

from apriltag_ros.

It's w.r.t. the centre.

TL;DR: This comment can be found in the source:

these frames together with cv::solvePnP directly avoids
// AprilTag 's frames altogether

And the object points that are solved for are distributed tag_size/2 around 0,0,0 in the x,y plane here:

objectPoints.push_back(T_oi.get_minor<3, 4>(0, 0)*cv::Vec4d(-s,-s, 0, 1));
objectPoints.push_back(T_oi.get_minor<3, 4>(0, 0)*cv::Vec4d( s,-s, 0, 1));
objectPoints.push_back(T_oi.get_minor<3, 4>(0, 0)*cv::Vec4d( s, s, 0, 1));
objectPoints.push_back(T_oi.get_minor<3, 4>(0, 0)*cv::Vec4d(-s, s, 0, 1));

from apriltag_ros.

@rgreid thank you

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