# What is the message of geometry_msgs/PoseWithCovariance

Hi, I'm using ROS kinetic in ubuntu 16.04 and still think I'm new to ROS.

Anyway, I'm making some packages above on people tracking so I need to estimate people's state and their covariance in 2D circumstance.

And I found the ROS message of geometry_msgs/PoseWithCovariance and geometry_msgs/TwistWithCovariance.

These covariance terms have 36-length of a list, so I think they correspond to [x, y, z, roll, pitch, yaw] terms row and column each other.

The problem is I have no idea how to access them. When I'm gonna get the value of (row 3, col 4), where is it? Is it CUSTOMIZED_MSG_NAME.covarianve[15] ?

In other words, when I inspect from CUSTOMIZED_MSG_NAME.covarianve[0] to [5], is these values correspond to the all first row of the covariance matrix(list in ROS message) ?? or column ??

Thanks in advance :)