Anyone who has ever installed a GPS backed NTP appliance in a data center can quickly answer that.
For those who haven’t: it involves drilling holes in the roof of your data center for a satellite antenna.
For those who haven’t: it involves drilling holes in the roof of your data center for a satellite antenna.
If you mainly care about time and can tolerate a few microseconds of error, usually being able to see 4 satellites might well be enough.
I remember seeing a gps receiver designed just for time that could maintain sync using only one satellite (it assumed that it was bolted to an immovable object, and it might have needed to see 4 satellites at once at some point).
To get halfway decent holdover performance, you want all the precision you can get when the constellation is good. That requires the best skyview (and least multipath) you can manage.