Note the following:
These are extremely high accuracy (cm level accuracy with an active reference base station) that might be useful for truly autonomous robots.
The first is an extremely high accuracy GNSS (GPS) receiver for < $50.
The second is an insanely accurate GNSS receiver for about $300 (±)
I don’t know if you folks are interested in this, but here it is.
Waveshare has other, less accurate and less expensive options too.
They also have GPS systems that are anti-jamming and counteract multi-path reflected signal distortion.