It might have happened to you: your RTK receiver is in RTK FIXED, reporting centimeter precision and you are happily doing very accurate measurements. You go back to your desk and compare your results with the measurements from another day or from another person. And you get a big surprise: there is an offset!
It’s a complex topic, but especially on applications that involve comparing to maps it is important to understand in which reference frame system are you doing your measurements?
u-blox just launched a very well explained white paper providing an overview of various coordinate reference frame systems and their role in calculating GNSS correction data. When evaluating a GNSS correction service, users often need to compare services. Detecting a significant offset between the two indicates using different reference frames.
You can learn more in the u-blox whitepaper about coordinate reference frame systems.