Medium Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Confusion; Situational Awareness; Time Pressure
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew FLC Overrode Automation; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Airspace Structure; Environment - Non Weather Related
On the flight from IAD; after takeoff; the instruction to proceed LND VOR as part of the flight plan. After a short time after making our way to the previously mentioned navigational aid; ATC called us asking to confirm we were heading to the correct VOR. I was the pilot monitoring in the flight and because of the GPS outage; I had my needles in 'green' which is a ground base navigation as a backup for the FMS. We asked for vectors to proceed to the right direction and no issues or alerts associated. As we kept going along the route; we tried to navigate by VOR navigation only and the green needles in the two VOR's were giving us erroneous and unreliable information. ATC had to correct our course several times and at the end; the Captain advised that our plane was not the only one with this issue.
First Officer reported they were receiving erroneous and unreliable VOR information during a GPS outage.