# ARConfiguration.WorldAlignment.gravity The coordinate system’s y-axis is parallel to gravity, and its origin is the initial position of the device. ``` case gravity ``` ## Discussion The y-axis matches the direction of gravity as detected by the device’s motion sensing hardware; that is, the vector `(0,-1,0)` points downward. The position and orientation of the device as of when the session configuration is first run determine the rest of the coordinate system: For the z-axis, ARKit chooses a basis vector `(0,0,-1)` pointing in the direction the device camera faces and perpendicular to the gravity axis. ARKit chooses a x-axis based on the z- and y-axes using the right hand rule—that is, the basis vector `(1,0,0)` is orthogonal to the other two axes, and (for a viewer looking in the negative-z direction) points toward the right.  --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)