rviz odometry is doubling angle?

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Hello all, I'm having some problems visualizing odometry with rviz. The problem I am encountering is that rviz appears to be doubling the angle given by the odometry message published:

When the orientation.z of the odometry message is 0.00 (as viewed by rostopic echo odom), the arrow in rviz is aligned vertically with a gridline, as expected

When the orientation.z of the odometry message is 1.58, the arrow in rviz is anti-parallel to the 0.00 arrow from before (~180 degree rotation = ~3.14 radians is approx. 2 * 1.58 radians)

When the arrow on rviz is perpendicular to the initial 0.00 arrow, the orientation.z reads about .707 radians = ~40 degrees.

I'm not too sure if this is a configuration error or not - I originally thought I had written my odometry publisher incorrectly until I started echoing the topic.

Any help would be greatly appreciated.

Relevant Code:

                //since all odometry is 6DOF we'll need a quaternion created from yaw
                geometry_msgs::Quaternion odom_quat = tf::createQuaternionMsgFromYaw(
                                bot->m_odometry_yaw);

                //first, we'll publish the transform over tf
                geometry_msgs::TransformStamped odom_trans;
                odom_trans.header.stamp = current_time;
                odom_trans.header.frame_id = "odom";
                odom_trans.child_frame_id = "base_link";

                odom_trans.transform.translation.x = bot->m_odometry_x;
                odom_trans.transform.translation.y = bot->m_odometry_y;
                odom_trans.transform.translation.z = 0.0;
                odom_trans.transform.rotation = odom_quat;

                //send the transform
                odom_broadcaster.sendTransform(odom_trans);

                //next, we'll publish the odometry message over ROS
                nav_msgs::Odometry odom;
                odom.header.stamp = current_time;
                odom.header.frame_id = "odom";

                //set the position
                odom.pose.pose.position.x = bot->m_odometry_x;
                odom.pose.pose.position.y = bot->m_odometry_y;
                odom.pose.pose.position.z = 0.0;
                odom.pose.pose.orientation = odom_quat;

                //set the velocity
                odom.child_frame_id = "base_link";
                odom.twist.twist.linear.x = bot->m_velocity_x;
                odom.twist.twist.linear.y = bot->m_velocity_y;
                odom.twist.twist.angular.z = bot->m_velocity_yaw;

                //publish the message
                odom_pub.publish(odom);