Brainstorming: Improving navigation without using GPS

My narrowest passage is about 50 cm wide (the mower is 44 cm wide).
If the distance to drive in the passage is < 10 meters the RFID solution can help to localisation on perimeter and drive using IMU
Yes, I can well imagine.
Since the mower drives between the tightly laid perimeter wire, I steer against it when it crosses the wire (two perimeter sensors). To do this, I always stop the opposite rear wheel - the rest is calculated by the 4-wheel function. This works very well if the speed is not too high.

I do not want to accept that there is no other (simple) way to locate the mower in a coordinate system.