I’m surprised no one has mentioned OPUS – the Online Positioning User Service.
OPUS can help fix the absolute (real) location of a stand-alone (uncorrected) L1/L2 base station (such as the RS2) to within a few centimeters with observations of 15mins to >24 hours depending on the location & quality of GNSS reception:
https://www.ngs.noaa.gov/OPUS/about.jsp#about
Note: you do need an internet connection of some kind in order to submit (upload) raw GNSS / RINEX logs to the OPUS servers. This is a post-processing step that can be done any time, it does not require a real-time internet connection.