None.

Rule & of the Navigation Rules states: Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.
It's a different contaxt but the principle applies.

You do not base decisions on scanty information, if you can avoid doing so. I'm with you in that I rarely use a GPS, for real navigation. When I do use it, it is almost exclusively to estimate the driving time to my destination.

When you are out in the middle of nowhere, you would not be wise if you rely solely on a GPS. If you cannot figure out how to navigate without the GPS, you are going to be in big trouble when it fails. But doesn't the same ring true when you cannot see the landmarks on the map?

When I went to sea, I used the satellites and took the celestial.