Defining space over 20 feet

Hey everyone, I have a 20 foot linear rail set up with UR10E and was looking at how to define the plane, any ideas on how to set it up so the robot knows its location within that span? we are working with some uneven floors, and the only solution I could think of was to set multiple plans and call them as needed. I’m fairly new to all of this so any and all help would be much appreciated. As of right now we are using manual indexing.