Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Environment - Non Weather Related
While in cruise; received several messages from ATC that we were slightly off course.  It appeared our FMS and GPS were not giving correct position information; despite following the procedure in the FOIB regarding the ADSB out of service.  We eventually had to request radar vectors until we could confirm green needle backup and continue our course via green needles.  Flight continued with no further problems. Discussed the issue with maintenance and they said to write up the FMS and GPS. FMS and GPS not giving correct location data to pilots. Request vectors earlier before problem continues to get worse.
Reporter offered no new information.
CRJ-200 First Officer reported navigation problems associated FMS and GPS related issues.