I imagined this information would be easy to find but it has turned out far more difficult than expected.
I was hoping to find a well done comparison of the real world accuracy of the currently (partially/fully) operational GNSS systems. I'd like to first point out the problems I've noticed with the sources/methodology/info that I've come across in my search to better convey both what I hope to avoid and to find.
Problems with information I've stumbled upon so far...
1) simple claims of the superior accuracy of a certain GNSS, often made authorities/directors/admins with direct ties/stakes to said system (often quoted/repeated by lay media w/out "showing work").
2) simple statements that only reflects some idealized scenario (accuracy at a place with perfect atmospheric & geographic conditions and fully augmented by additional ground/location signals/sensors). Worse yet, a comparison of one system under the previously mentioned conditions vs another in adverse/non-augmented conditions.
3) some dude's blog where he took two receivers out on a hike, looked at them from a nice lookout spot, and reported which he thought was most accurate.
4) some extraordinarily detailed paper covered in greek letter filled integrals & derivatives that doesn't really answer my question as the main topic was some sort of doctoral thesis about some atmospheric effect on doppler and brownian motion bla blah. (I'm a scientist myself but this isn't my area, I'm looking for something understandable to an educated individual that's willing to suffer some hard reading but I have limits, hopefully you know what I mean as I think there are a ton of 'us' on this particular forum).
5) something published >10 years ago.
6) something about how multiple/fusion of GNSS systems is most accurate (see this all the time in my search results).
Now what I'm hoping to find...
1) something with the data/technicals, at least somewhere, to back up any findings/claims. I don't want to have to go learn/re-learn some advanced mathematics, would prefer a source/author that does enough 'handholding' for it to be understandable by a person without direct professional involvement in the area but with a technical aptitude & background, but it never hurts to have the hardcore stuff for a reference.
2) something contemporary (preferably at a point in time where each GNSS at least had enough birds in the sky to cover the test location with a quality of service that should reasonably represent expected quality of service once fully operational).
3) I would prefer the comparison be of the civilian signals with a high quality commercially available receiver. (I don't see how a comparison could possibly be made of military signals outside being purely theoretical estimates).
4) I would prefer a comparison of accuracy purely from space based signals at the receiver, as someone might experience in a vast desert as opposed to some lab or area with lots of ground based augmentation.
5) I understand that it's possible, probably even necessary for some people/professionals in the area, to be pedantic about certain aspects like "well, what do you mean by 'accuracy'?" or "sometimes 'accuracy' isn't the best measure of performance" or "there are other things to consider" or "that's not going to work in an 'urban canyon'" etc... That's not really what I'm curious to know/consider. Just simple stationary accuracy in 3-dimensional space of unaugmented and contemporary GNSS systems, head to head, as would be expected/possible using a high quality/pro-grade commercial receiver in an average, neither in an adverse(mid-town manhattan) nor ideal (Atacama?) conditions.
Is this a realistic hope/inquiry? I can't seem to find such source, which I find surprising for some reason. I would HUGELY appreciate some pointers/links to material that fits the bill on this. If you feel so inclined to take this question on in detail, personally, right here, just know that I will take up nightly prayer and beg the gods to bestow good health & riches on you and your family for the rest of time! It's worth a shot.