Bear in mind that I know very little about this system yet, but, AUIU, you kinda set that length of time based upon how you set the parameter, (something like) “acceptable precision.” It seems like a logarithmic response time. Past a certain setting, it can take DAYS to get even close to low centimeter precision at least in my environment. Some settings may never converge. However, after you get “close enough,” the rovers can lock in at 0.03 – 0.01 meters! Then, if you can relate the “frozen/locked” location/altitude to a real GCP, you can do some quick post processing and correct all the rover values to actual. For my applications (so far) less than a meter off of real is entirely satisfactory. Harder to get there in the vertical.
Sven, what message and content does one look for, please?
UBX-NAV-SVIN reports if the survey is ongoing or complete.
I would not use SURVEY-IN mode. Better to post-process raw measurements against a governmental reference (Marker, CORS, etc), or get a competent surveyor to do one.