I would like to use either the RTK Express or Facet to take a measurement (over some time), submit it to a corrections for offline / non-realtime correction, and get my coordinate information there. This is an area without RTK source, and which I will only ever take the 1 measurement in this location.
I’ve done this when setting up a permanent base station, but the software I used for the base station kept the log and provided all the conversions, etc., and is definitely not for field use.
Do any of the android apps have a means by which they can collect the data file and then upload it for offline correcting?
If you can record UBX-RXM-RAWX (Observations) and optionally UBX-RXM-SFRBX (Navigation) you can generate RINEX files which can be post-processed.
Commercially tools like Carlson Survey GNSS, which uses WaSoft’s WA2
Depending on location NOAA has data from CORS sites in US and territories (including world-wide ephemeris station combination), Ordnance Survey in UK.