alt Hacker NewsThis is a judgment issue more than a skill issue.
GPS NOTAM'd as unreliable on a dark, moonless night?
Fly the ILS approach (or fly a visual approach along the track of the ILS approach backing up your visual with the radio signals). That will give you terrain and obstacle clearance all along the route using locally generated navigation signals that will be entirely unaffected by GPS jamming.
Per other comments the ILS approach was not available due to the local weather service being NOTAM'd as unavailable, couldn't set local altitude. The judgment call was effectively whether to take the flight at all, as there was effectively no instrument approach available and the visual conditions precluded VFR.