Hi，team.

When I add `runtime_parameters.measure3D_reference_frame = sl in depth_sensing this code. REFERENCE_FRAME. WORLD`

, the coordinate system y-axis on which the obtained point cloud depends is always parallel to gravity.

When I write my own code, I added `coordinate_system=sl. COORDINATE_SYSTEM. RIGHT_HANDED_Y_UP`

and `runtime_parameters.measure3D_reference_frame = sl. REFERENCE_FRAME. WORLD`

the y-axis of the coordinate system on which the point cloud I get is not parallel to gravity.

What’s going on here?

The default reference frame if none is specified is `sl.COORDINATE_SYSTEM.IMAGE`

, where the +Y axis points down (and so would be parallel to gravity).

If you use `sl.COORDINATE_SYSTEM.RIGHT_HANDED_Y_UP`

the +Y axis will point *up*, and so it would be in the opposite direction of gravity.

Check out COORDINATE_SYSTEM Class Reference | API Reference | Stereolabs for a description of all the coordinate systems.

Thank you for your reply！

Can I understand it this way，as long as I set it up `runtime_parameters.measure3D_reference_frame = sl. REFERENCE_FRAME. WORLD`

there will be an axis parallel to gravity.

Hi @zore017

Fully by default, yes, because set_gravity_as_origin is true by default. If you set it to false, you won’t have an axis parallel to the gravity.

As @JC31 said, by default, it’s the Y axis that would be pointing down, so if you leave set_gravity_as_origin to true, Y will be parallel to gravity in sl. REFERENCE_FRAME. WORLD.

In CAMERA, Y will be toward the bottom of the camera.

I understand，so，with the Y axis remaining parallel to gravity, how are the other two axes set?

Can I set set_gravity_as_origin?

Also,I want to say，thanks to your team for this camera product, it is really amazing！

Thanks for the kind words

set_gravity_as_origin overrides the roll and the pitch of the camera using IMU data. The yaw is set using the direction the camera is facing.

Talking about axes,

- the Y axis would be parallel to the gravity
- the Z axis (forward) would be the forward of the camera projected in the plane orthogonal to Y
- the X axis would be the right axis projected in the plane orthogonal to Y

Thank for your patient answer！