Merge "improve documentation for the ROTATION_VECTOR sensor"
diff --git a/core/java/android/hardware/SensorEvent.java b/core/java/android/hardware/SensorEvent.java
index a3ce9f5..b111b84 100644
--- a/core/java/android/hardware/SensorEvent.java
+++ b/core/java/android/hardware/SensorEvent.java
@@ -253,6 +253,23 @@
* <p>Elements of the rotation vector are unitless.
* The x,y, and z axis are defined in the same way as the acceleration
* sensor.</p>
+ * The reference coordinate system is defined as a direct orthonormal basis,
+ * where:
+ * </p>
+ *
+ * <ul>
+ * <li>X is defined as the vector product <b>Y.Z</b> (It is tangential to
+ * the ground at the device's current location and roughly points East).</li>
+ * <li>Y is tangential to the ground at the device's current location and
+ * points towards the magnetic North Pole.</li>
+ * <li>Z points towards the sky and is perpendicular to the ground.</li>
+ * </ul>
+ *
+ * <p>
+ * <center><img src="../../../images/axis_globe.png"
+ * alt="World coordinate-system diagram." border="0" /></center>
+ * </p>
+ *
* <ul>
* <p>
* values[0]: x*sin(θ/2)