Reference Frame

Optical Frame

When you do cameras, they are expressed in the optical frame.

For ROS, the convention is that you add _optical to specify the extra convention.

The standard convention for ROS is to have $x$ in the direction that the robot is moving in. For $z$, the robot looking up.

We don’t like this for cameras, because we like to work exclusively in $x$ and $y$, therefore the $z$ serves as like the “depth”.

• Source: https://www.fdxlabs.com/calculate-x-y-z-real-world-coordinates-from-a-single-camera-using-opencv/

So X is the Row, Y is the column.

• When we index into an image, we do img[Y][X].

And notice that the image points down.

Other Notes

I noticed the case such as in the Cyrill Stachniss course that the y-axis is horizontal, and the x-axis is vertical.

• I assume that this is the case because there are