diff --git a/README.md b/README.md
index fd992cd..d2635bb 100644
--- a/README.md
+++ b/README.md
@@ -35,7 +35,9 @@ catkin_make -DCMAKE_BUILD_TYPE=Release
 
 ## Parameters
 All configurable parameters are listed in *launch/hdl_localization.launch* as ros params.
-The estimated pose can be reset using using "2D Pose Estimate" on rviz
+The estimated pose can be reset using using "2D Pose Estimate" on rviz.
+The parametor *odom_covariance_coefficient* is a coefficient of odom covariance.
+Odom covariance is caluculated from ths fitness score of scan matching.
 
 ## Topics
 - ***/odom*** (nav_msgs/Odometry)