diff --git a/rpcs3/Emu/Cell/Modules/cellGem.h b/rpcs3/Emu/Cell/Modules/cellGem.h
index 832e7aac19..6f49d568b4 100644
--- a/rpcs3/Emu/Cell/Modules/cellGem.h
+++ b/rpcs3/Emu/Cell/Modules/cellGem.h
@@ -159,10 +159,10 @@ struct CellGemPadData
 
 struct CellGemInertialState
 {
-	be_t<f32> accelerometer[4];
-	be_t<f32> gyro[4];
-	be_t<f32> accelerometer_bias[4];
-	be_t<f32> gyro_bias[4];
+	be_t<f32> accelerometer[4];      // accelerometer readings including accelerometer_bias (G units)
+	be_t<f32> gyro[4];               // gyro readings including gyro_bias (radians/s)
+	be_t<f32> accelerometer_bias[4]; // accelerometer bias (G units)
+	be_t<f32> gyro_bias[4];          // gyro bias (radians/s)
 	CellGemPadData pad;
 	CellGemExtPortData ext;
 	be_t<u64> timestamp;
@@ -178,17 +178,21 @@ struct CellGemInfo
 	be_t<u32> port[CELL_GEM_MAX_NUM];
 };
 
+// origin is the center of the camera
+// x increases to right (facing the camera)
+// y increases upwards
+// z increases towards user (away from the camera)
 struct CellGemState
 {
-	be_t<f32> pos[4];
-	be_t<f32> vel[4];
-	be_t<f32> accel[4];
-	be_t<f32> quat[4];
-	be_t<f32> angvel[4];
-	be_t<f32> angaccel[4];
-	be_t<f32> handle_pos[4];
-	be_t<f32> handle_vel[4];
-	be_t<f32> handle_accel[4];
+	be_t<f32> pos[4];          // center of sphere (mm)
+	be_t<f32> vel[4];          // velocity of sphere (mm/s)
+	be_t<f32> accel[4];        // acceleration of sphere (mm/s²)
+	be_t<f32> quat[4];         // quaternion orientation (x,y,z,w) of controller relative to default (facing the camera with buttons up)
+	be_t<f32> angvel[4];       // angular velocity of controller (radians/s)
+	be_t<f32> angaccel[4];     // angular acceleration of controller (radians/s²)
+	be_t<f32> handle_pos[4];   // center of controller handle (mm)
+	be_t<f32> handle_vel[4];   // velocity of controller handle (mm/s)
+	be_t<f32> handle_accel[4]; // acceleration of controller handle (mm/s²)
 	CellGemPadData pad;
 	CellGemExtPortData ext;
 	be_t<u64> timestamp;