Elevation in Hector Slam

[rob3a]

I am using hector slam but also going through ramps, I can get the tf from base_stabilizer to base_link with imu_to_tf node but the problem is how can I get the heigh in pose (z) which is the tf between base_footprint to base stabilizer. This references are from:
http://wiki.ros.org/hector_slam/Tutorials/SettingUpForYourRobot
Any help?