Update README.md

Author: gitouni

README.md

@@ -12,7 +12,7 @@ Official Implementation of **Motion-based Lidar-camera Calibration via Cross-mod
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 |![](./doc/traj_04.jpeg)|![](./doc/traj_05.jpeg)|![](./doc/traj_07.jpeg)|
 
-These trajectories are not suitable for hand-eye calibration because of lack of adequent rotational motions in at least two directions. Other hybrid methods may also suffer from the bad initial extrinsic estimation from hand-eye calibration. We believe this proposed method offers a valuable tool to resolve this problem.
+These trajectories are not suitable for hand-eye calibration because of lack of adequent rotations around at least two directions. Other hybrid methods may also suffer from the bad initial extrinsic estimation from hand-eye calibration. We believe this proposed method offers a valuable tool to resolve this problem.
 # Performance on KITTI Odometry
 * `rotation units`: degree
 * `translation units`: cm