# ARConfiguration.WorldAlignment.gravityAndHeading The coordinate system’s y-axis is parallel to gravity, its x- and z-axes are oriented to compass heading, and its origin is the initial position of the device. ``` case gravityAndHeading ``` ## 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 x- and z-axes match the longitude and latitude directions as measured by Location Services. The vector `(0,0,-1)` points to true north and the vector `(-1,0,0)` points west. (That is, the positive x-, y-, and z-axes point east, up, and south, respectively.)  Although this option fixes the *directions* of the three coordinate axes to real-world directions, the *location* of the coordinate system’s origin is still relative to the device, matching the device’s position as of when the session configuration is first run. > Note: > Using gravity and heading alignment requires tracking the device’s geographic location. Your app’s Info.plist must include user-facing text for the [NSLocationUsageDescription](https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CocoaKeys.html#//apple_ref/doc/plist/info/NSLocationUsageDescription) or [NSLocationWhenInUseUsageDescription](https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CocoaKeys.html#//apple_ref/doc/plist/info/NSLocationWhenInUseUsageDescription) key so that the user can grant your app permission for location tracking. --- 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)