Start MAVROS (from anywhere):
roslaunch mavros px4.launch
And launch terpcopter:
roslaunch terpcopter_commander terpcopter_commander.launch
run offboard mode:
rosrun mavros mavsys mode -c OFFBOARD
arm the vechile:
rosrun mavros mavsafety arm
rossrv show [service name]
rosservice call [service name] [arg]