Which topic to use

I am using px4 and making a simulation on gazebo I want my drone to keep moving in specific direction without keep updating this topic “mavros/setpoint_position/local” I mean for example a topic on which I keep it’s x = 1 so it keep my drone moving by 1 unit every publish
for clarification I am trying to do a line following drill using a drone and a camera pointing down so I want that my drone to keep moving forward and I just control it’s orientation