Regional Jet 700 ER/LR (CRJ700)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Human Factors
Due to nationwide ADS-B and transponder issues; we were dispatched with 3 MELs covering the transponders and GPS system; and assigned an airway route clearance instead of the usual RNAV SID. The Captain (Pilot Flying) elected to fly in white needles; while I (Pilot Monitoring) used green needles to verify proper navigation. I informed both Norcal Departure and Center that we were negative GPS and could not accept direct clearances. Approximately halfway to ZZZ we were cleared direct ZZZZZ; an initial fix for the ZZZ ILS/DME 32. I told the Controller we could not accept a direct clearance; but could accept a vector. The Controller gave us a vector; which we complied with. However; I believe the Captain may have executed a 'direct-to' using the FMS; and flew white needles to ZZZZZ instead of the heading. I was distracted by the descent check and other duties; and did not notice that we were flying slightly off the assigned heading. As we neared ZZZZZ; the Controller told us that we were 10 to 20 degrees off course; and gave us a new vector which we complied with. We then picked up the localizer course and completed the approach. It was then that we finally realized that the FMS depicted position was about 15 miles off our actual position (it was VMC and we could see where we were.) This distraction resulted in much discussion about the navigational error; to the point that the Pilot Flying delayed the proper landing configuration calls beyond the usual point. At 1;500 feet AGL we were still at Flaps 8 with gear up; I asked 'Are you going to call for the gear?' The Pilot Flying called for gear down; Flaps 30 -- but we were only at Flaps 8 because he had only called for Flaps 8 previously. The end result was that we reached proper landing configuration at about 900 feet HAT; instead of 1;000 feet HAT.The cause of the navigational error was the Pilot Flying's decision to fly in white needles rather than green; and our shared (mistaken) belief that the FMS position would be relatively accurate despite the MEL. On my part as Pilot Monitoring; I should have requested that the Pilot Flying fly in green needles. I did not notice the fact that after the Controller had given us a heading direct ZZZZZ; the Pilot Flying flew that heading for a while but then switched into white needles and NAV mode; which is what resulted in the heading change. In terms of the late configuration; the cause was our distraction caused by the navigational error that had just happened.Pilots should be reminded that even though the FMS position may appear to be accurate; a GPS deferral means that the FMS position is completely unreliable; and the airplane should be flown in green needles; regardless of how accurate the FMS appears.
Reporter stated the cause was a Rockwell Collins GPS issue related to a software update.  15 miles off course; FMS showing no error message; received vectors from ATC. Next day FMS showed them on course but were 25 miles off course.
CRJ-700 pilot reported a problem with the GPS system and having to flying with white needles instead of the green needles.