Mission in PX4

Hello everyone,
I am trying to create a mission in PX4 for fixed wing vehicle. I wonder few things:

  • Creating a landing pattern is really hard. Do you have any suggestions for this?
  • How to measure horizontal and vertical distances between different waypoints?
  • I am planning to assign a mission switch to an rc controller along with other modes such as manual, position, etc. to have a control in case of a problem. Is this the correct way to do this?
  • Do you have any other suggestions to have a better mission?

I really appreciate if someone could answer my questions.