Take off and Landing

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Hey, I am in the process of flying a drone and I need to do a takeoff, hover and land, should I just publish in /mavros/sepoint_attitude/cmd_vel a geometry_msgs/TwistStamped message to takeoff and for landing can I just do a for loop to decrease the published values to zero and for hovering I just do a PID to the IMU data. I am really new to this thing so Please can anyone tell if that might work or not and whether is there some already existing codes for that.

Knowing that I'm using Ardocopter

Another question in mavros extra there is a topic called ~vision_pose/pose

That uses IMU and Camera data to estimate the pose, In my case I don't have camera is that still working with just an IMU?

Thanks in advance