Air carrier Captain reported GPS jamming near Ankara airspace. The Captain states further west; when it was expected the instruments would operate; the GPS and ADS-C remained inoperative.

Narrative

As we approached the Ankara FIR on airway N37 we began to encounter the expected GPS interference for that area and switched off the GPS updating as per the GPS interference supplementary procedure. As one why flys this route regularly; this was routine for this area. When we were well to the west of the normal area of interference we determined that the aircraft was unable to reestablish GPS updating. We were also unable to establish CPDLC but frequently it is unavailable in that area so we were not concerned with that. We had no cockpit indications that CPDLC or ADS-C were inoperative; just inoperative GPS updating; Terr pos and ADS-B.At this point it was time for the relief crew to take over. When they came up to the cockpit; all four crew members remained in the cockpit and we conducted an extensive briefing on what we knew about the problem and the potential ramifications for the ocean crossing. I left the the cockpit with instructions to call me if it appeared that a diversion was going to be necessary and the understanding that the other crew would contact dispatch and maintenance control to formulate a plan. It is worth noting very specifically that the relief crew did exactly what I expected and reported to me exactly as I briefed. I was very comfortable with what they did.The relief crew reported that they determined that CPDLC and ADS-C was also inop and in coordination with dispatch determined that they had to do the Atlantic crossing at FL280. This left them without sufficient fuel to continue to ZZZ airport and a fuel stop in ZZZ1 airport was planned. The relief crew informed me of this; got my concurrence and made the necessary coordination with the cabin crew. I continued my rest.When I returned to the cockpit about an hour and a half out of ZZZ1 airport as a crew we noticed that there was significantly more fuel remaining than was planned. We did our own planning and then contacted dispatch for backup and determined that we could land in ZZZ with 13;000 pounds of fuel remaining; 8;000 pounds more than was originally thought. After recalculating and careful consideration we elected to continue to ZZZ. Dispatch re released us and the ATC desk notified ATC of our 'minimum fuel status.' We proceeded to ZZZ and landed with about 12;500 pounds of fuel on board. Although we did state minimum fuel; we did not; at any time request priority handling; nor was it necessary.I have several concerns; why was the fuel calculation to ZZZ1 so far off? 8;000 lbs seems a large discrepancy. Why did the CPDLC and ADS-C fail? Was this a separate or related problem? Why were we unable to restore GPS updating? Ultimately it did fix itself in the middle of the Atlantic. It is my understanding that this is not the first time this has happened; perhaps some guidance is appropriate? Maybe a procedure or an addition to the GPS spoofing procedure? There really needs to be better; more readily accessible information on what equipment is required to enter certain airspace. (IE NAT high level airspace) Ultimately it was pointed out to me where is was but; c'mon. Lastly; there was a huge amount of contradictory information given to the flight attendants and passengers regarding the divert to ZZZ1. The passengers were being given alternative routings from ZZZ1 (even though we were planned on a hardstand.) The Flight attendants were being told that the flight was being re crewed. Both situations were not legal for us. We were originally told that the flight was going to be recrewed; then that we were going to operate it (barely legal under the absolute best of circumstances. All of this generated confusion and potential distraction and was unacceptable from both a safety and passenger/crew service standpoint. Although this was emphatically not a factor in my decision to continue; it was clear to me that if we landed in ZZZ1; the aircraft was; in reality; not going anywhere for a long; long time because of the total lack of coordination.