What datum is my data in

[DavidWLane]

I am collecting location data using high resolution GPS with RTK correction.  The equipment I am using is an arrow gold setup to collect using geoid 18 NAV88/NAD83(2011)

I have three known referenced locations that I have been tracking and we are getting altitude results within 0.1' of the reference and horizontal within 0.3' of reference.  The reference is using NAV88/NAD83(2011)

Being new in all of this, I noticed after a year of collecting data that the datum for my feature is WGS84 Web mercaptor.  If I am understanding things correctly, I should then see an offset of about 1.5 - 2 feet.  And I am not.

Is Suvey123 looking at that data and assuming that it is WGS84, and giving results as if it is?  If Survey123 is doing some kind of data transformation, what is it?

[ZenMasterZeke]

I think that AGOL, and possibly Enterprise, S123, etc., display data in Web Mercator, converting on the fly similar to Pro, where layers can have a different cs than the map. This doesn't change the features' actual cs. I'm not an expert on troubleshooting cs's though, so might well be wrong.

[DavidWLane]

Sorry, I am as dense as a rock what does "CS" stand for?

[DavidWLane]

I think I figured out CS coordinate system,  dang I can be slow some mornings.