@Susan Smith great question, and honestly the constellation coverage detail is exactly the right thing to dig into before committing to a module for a multi-region build.
I don't have the full constellation breakdown documented in front of me right now, so I don't want to throw out a spec I'm not certain of — but given that 1.5m accuracy at 18Hz is what they're quoting, that kind of performance doesn't come from GPS-only. You'd typically need multi-constellation fusion to hit those numbers consistently, especially across different geographic regions. GPS-only at 18Hz in SE Asia or dense EU urban environments would degrade pretty noticeably.
My suggestion would be to post this directly to the RFOXiA team or tag Moamen in here — they're pretty responsive and this is exactly the kind of technical pre-sales question that deserves a straight answer from the source rather than community speculation. The urban canyon concern is legit and worth getting confirmed before you build your tracking architecture around it.
