PX4FLOW with Offboard mode

Hi, I am working on autonomous hovering with

  1. Odroid XU4 (ubuntu 16.04)
  2. px4flow (http://wiki.ros.org/px4flow_node) .

I successfully achieved offboard hovering using using GPS (https://dev.px4.io/v1.9.0/en/ros/mavros_offboard.html).

What I want to do now is autonomous hovering using px4flow sensor (no gps) with offbaord mode.
I am still looking for tutorial of autonomous hovering, but I cannot any example for offboard mode with px4flow…

Could you help me to develop this quadrotor?
Is there anyone who can explain how to integrate and use it for hovering?

Thank you in advance.